Construction and Building Materials(2022 - 2023)
Investigating the effects of cracks and low-calcium supplementary cementitious materials on steel fiber corrosion in cement paste
Chaimongkhol C.; Medepalli S.; Zheng Y.; Matsuda T.; Ishida T.; Wang T.
Construction and Building Materials, Elsevier Ltd., Vol.399, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2023.132554)
Abstract
Exposure of steel fibre reinforced concrete (SFRC) to chlorides can result in corrosion that lowers its performance. However, studies examining the extent of corrosion in SFRC are currently limited, as existing corrosion monitoring techniques are either destructive or not applicable to steel fibres due to their small size. In this paper, a reliable non-destructive approach is developed based on electrical resistance technique to continuously measure corrosion development in steel fibre in cement paste. The effects of cracks and supplementary cementitious materials (SCMs) on steel fibre corrosion are investigated. The experimental results show that the corrosion rate of steel fibre is critically controlled by the [Cl?]/[OH?] ratio of the pore solution. Regardless of the chloride content, uncracked cement paste was found to effectively protect steel fibre from corrosion by reducing the likelihood of its exposure to oxygen and water. In cracked cement paste, pitting corrosion occurred only at a high chloride content, while showing high resistance at lower chloride contents. Different SCMs have shown different effects on corrosion resistance, mainly owing to their varying chloride binding capacity. Metakaolin blend efficiently resists the corrosion of steel fibre. Silica fume blends exhibit the highest corrosion levels, which are even higher than the corrosion exhibited by ordinary Portland cement in the presence of a crack. c 2023
Synergetic effect of fly ash and ground-granulated blast slag on improving the chloride permeability and freeze?thaw resistance of recycled aggregate concrete
Chen C.; Lu C.; Lu C.; Wei S.; Guo Z.; Zhou Q.; Wang W.
Construction and Building Materials, Elsevier Ltd., Vol.365, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2022.130015)
Abstract
In this study, the synergetic effects of fly ash (FA) and ground-granulated blast slag (GGBS) on the compressive behavior and durability of recycled aggregate concrete (RAC) were comprehensively investigated. FA and GGBS were incorporated separately or simultaneously into the RAC containing 0%, 35%, and 50% recycled coarse aggregate (RCA) to replace partial cement. Moreover, the frost resistance and chloride penetration resistance of RAC, respectively, were experimentally determined by the rapid freeze?thaw cycle test and rapid chloride permeability test (RCPT). Results showed that an optimum replacement ratio could exist for improving the properties of RAC by partially replacing cement with FA and GGBS. The optimum ratio of the simultaneous incorporation of FA and GGBS to replace partly cement for improving the 90-day-compressive strength and the chloride penetration resistance of RAC were 10% and 20%, respectively, but for enhancing the frost resistance of RAC were 15% and 15%. In addition, the synergetic effects of simultaneously incorporating FA and GGBS were more effective than the effects of separately incorporating FA or GGBS on enhancing the performance of RAC. When adopting the simultaneous incorporation of 15% FA and 15% GGBS, the 90-day-compressive strength, chloride penetration resistance, and frost resistance of RAC incorporating 50% RCA were better than those of ordinary concrete. c 2022
A new apparatus for investigating gas transport property in geomaterials with ultralow permeability
Cui L.-Y.; Ye W.-M.; Ji Y.-H.; Xu L.; Ye G.-L.; Ye B.; Chen B.; Cui Y.-J.; Zhang F.
Construction and Building Materials, Elsevier Ltd., Vol.385, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2023.131523)
Abstract
The gas flow in geological materials with ultra-low permeability can vary dramatically, i. e., from almost no measurable quantity of gas before breakthrough to a massive gas flux at breakthrough. It is a great challenge to realize the whole process measurement of gas transport in saturated geomaterials with ultra-low permeability. In this work, a newly designed temperature-controlled triaxial apparatus was developed. In which, a water-to-gas-exchanger was designed for precise injection of gas at a constant pressure or constant injection rate, due to that water is less compressible and much more difficult to leak through the seal of a regulator. Meanwhile, eddy current sensors and displacement transducer with high resolutions were utilized to accurately measure the specimen deformation at different locations in a non-contact way to explore the mechanism of gas entry and breakthrough. In addition, a gas flow detection device that contains four gas flowmeters with different measurement ranges and can automatically switch between these flowmeters was developed to monitor the gas outflow of the whole process. To validate the performance of the developed apparatus, systematic gas injection tests on Gaomiaozi (GMZ) bentonite were conducted, during which the helium gas was injected in a constant rate. Real-time data on inlet gas pressure, gas outflow rate, stress state (both isotropic and axial stresses) and volume deformation (both axially and radially) were monitored. Results show that the developed apparatus could successfully capture the gas entry and the subsequent breakthrough points of the compacted bentonite with ultralow permeability. For compacted bentonite with high saturation, capillary flow, dilatant flow and interfacial leakage could co-exist during the gas transport process and the dominated mechanism was closely related to the gas injection pressure. c 2023 Elsevier Ltd
Cyclic bond behavior and bond stress-slip constitutive model of rebar embedded in hybrid fiber reinforced strain-hardening cementitious composites
Ding Y.; Liu J.-P.; Yao G.; Wei W.; Mao W.-H.
Construction and Building Materials, Elsevier Ltd., Vol.369, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2023.130582)
Abstract
In this study, direct pullout tests were conducted to illustrate the influences of fiber types (polyethylene (PE) fiber, steel (ST) fiber and hybrid PE/ST fiber), rebar diameter (20 mm, 25 mm, 32 mm), matrix strength (50 MPa and 70 MPa), and loading procedure (monotonic and cyclic loading) on the bonding performance between rebar and strain-hardening cementitious composites (SHCC). The effects of design parameters on bond behavior under monotonic loading, as well as degradation laws of bond strength, bond stiffness, and energy dissipation capacity under cyclic loading are discussed in detail. Experimental results indicate the synergic effect of hybrid fiber is beneficial to crack arrest, bond strength, and bond strength and bond stiffness retention. Compared with those under monotonic loading, SHCC specimens under cyclic loading exhibit similar ascending behavior while an obvious performance degradation at descending. Additionally, ST fiber behaved more effectively than PE fiber in improving the energy dissipation capacity. Furthermore, a cyclic bond stress-slip constitutive model with acceptable accuracy is developed to predict the cyclic bond behavior of rebar embedded in SHCC. c 2023 Elsevier Ltd
Development of elastic and plastic strains in concrete damaged by alkali?silica reaction during various compression loading tests
Farooq S.; Aoki G.; Fujishima M.; Miura T.; Nakamura H.
Construction and Building Materials, Elsevier Ltd., Vol.393, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2023.132099)
Abstract
In this study, the fracture process of concrete in the presence of alkali silica reaction (ASR) cracks under compressive stress was evaluated. Concrete specimens damaged by ASR expansion at various expansion levels were tested under monotonic, stepwise cyclic, and sustained compressive loadings to evaluate the change in mechanical properties. The evolution of expansion cracks under these loading conditions was assessed using digital image correlation (DIC). In stepwise cyclic and sustained loadings, the elastic and plastic strains generated under different stress levels were separately investigated to elucidate the stress resistance mechanism and the impact of expansion cracks on mechanical properties. An increase in the expansion level was found to remarkably decrease the elastic modulus of concrete but only slightly reduce the compressive strength. Using DIC, expansion cracks were observed with the accumulation of principal strain development even at low stress level. Elastic strains linearly developed in specimens with and without ASR damage, whereas plastic strains increased non-linearly with expansion. Despite the high plastic strains observed before reaching the peak load under stepwise cyclic and sustained loadings, the compressive strength and elastic modulus of concrete remained unchanged regardless of the loading pattern. Based on this evidence, the stress resistance mechanism in the cross-section of ASR-damaged concrete was explained. c 2023 Elsevier Ltd
Investigation on the impact of Thermo-Drying towards Freeze-Thaw cycle processing for recycled coarse aggregate
Gong F.; Wang Z.; Ning Y.; Yang L.; Zeng Q.
Construction and Building Materials, Elsevier Ltd., Vol.392, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2023.131914)
Abstract
The use of recycled coarse aggregate (RCA) is limited due to the presence of attached mortar (AM), which affects its performance. To overcome this limitation, traditional methods such as mechanical and chemical techniques have been used to remove AM from RCA and obtain natural aggregate (NA). Freeze-thaw cycles (FTC) processing has shown high efficiency in removing AM while causing negligible damage to the NA. This paper aims to investigate the impact of thermo-drying (TD) on the FTC processing quantitatively. The experimental data, ranging from micro- to macro-scale, was used to reveal the mechanism behind the process. To further analyze the impact of TD, a theoretical model was established to calculate the strain distribution of AM during FTC processing while taking into account the influence of TD. The findings suggest that TD has a positive impact on FTC processing. However, an integrated analysis is necessary to balance processing efficiency and energy consumption. This analysis will allow for the development of an optimized TD-FTC processing scheme. c 2023 Elsevier Ltd
Mesoscale discrete analysis of mechanical properties of recycled aggregate concrete based on Voronoi mesh
Gong F.; Yang L.; Wang Z.; Jia J.; Ning Y.; Ueda T.
Construction and Building Materials, Elsevier Ltd., Vol.370, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2023.130649)
Abstract
The application of recycled coarse aggregate (RA) to produce recycled aggregate concrete (RAC) requires the investigation of its mechanical properties. From literature review, it is found that the experimental data scatters in large extent and even contradictory results exist. Therefore, numerical tool is an appropriate option to evaluate the mechanical performance of RAC. In this paper, a mesoscale approach is adopted to simulate the compressive and tensile behaviors of RAC with different strength levels of old mortar and new mortar, attachment ratio of old mortar within RA and replacement ratio of RA. The numerical study of RAC is followed by the validation on normal concrete with different shapes of natural coarse aggregate (NA). Then parametric studies on RAC are conducted, based on which an empirical model is proposed to predict the compressive strength of RAC with the above-mentioned factors. Experimental data are also summarized to validate the model, which shows satisfied correlation with the predicted value. c 2023 Elsevier Ltd
Performance of Compression-free turnbuckle braces using partially fibered CFRP under cyclic load
Hamasaki M.; Yamamoto R.; Taguchi T.; Shimizu K.; Komiya I.; Nakajima K.; Matsumoto Y.
Construction and Building Materials, Elsevier Ltd., Vol.366, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2022.130149)
Abstract
Turnbuckle braces have been widely used as the seismic-resistant member of steel structures. Being a very slender member, the compressive resistance capacity is not considered in the structural design, but these braces buckle easily due to compressive forces, and the buckling deformation damages the finishing material and causes local plastic strain concentration and plastic fatigue failure. Based on this, the authors of this study developed a compression-free brace that can be easily installed on existing steel turnbuckle braces. We focused on the use of lightweight, high-strength carbon fiber reinforced polymer (CFRP) as a brace material and joined the CFRP rod to the existing steel turnbuckle braces through a pipe style turnbuckle body. The proposed compression-free brace uses partially fibered CFRP (PFCFRP) rods to absorb compressive deformation so that only tensile forces are applied to the brace, and out-of-plane deformation due to buckling is significantly reduced. In addition, the combined use of steel turnbuckle braces can be expected to absorb seismic energy by the plastic deformation of steel. PFCFRP rods are only fiberized in the middle position and the unfiberized position (CFRP rods positions) at both ends are used for the joints. They are molded by pultrusion because of their excellent cost-effectiveness, superior mechanical performance, and stability. The partially fibered sections are created without resin injection. PFCFRP rods are connected to the braces using a pipe-style turnbuckle body. The method used to fix the PFCFRP rod and the pipe-style turnbuckle body involves widening the end of the PFCFRP rod to drive a wedge and insert it into the turnbuckle body. Then, it is filled with steel balls and epoxy resin to prevent it from pulling out. Furthermore, we use the pipe-style turnbuckle body to connect the steel structure like a sleeve joint to provide easy and useful assembly. Two different tests were carried out to confirm the effectiveness of the compression-free braces. Firstly, testing of materials used in compression-free braces was conducted. The results of the tests were used to compare the strength of steel turnbuckle braces to clarify the scope of the application of compression-free braces. Next, cyclic loading tests were carried out on a full-scale steel structural frame to simulate the actual seismic bracing situation. The results show that the proposed compression-free braces have similar historical behavior to existing steel turnbuckle braces. Because the PFCFRP rod absorbs the compressive axial deformation, the out-of-plane deformation can be significantly reduced. These results demonstrate that the proposed compression-free braces using PFCFRP can provide a safe and applicable seismic bracing system. c 2022 Elsevier Ltd
Shear behavior of reinforced concrete beams repaired using a hybrid scheme with stainless steel rebars and CFRP sheets
Hasan M.A.; Akiyama M.; Kojima K.; Izumi N.
Construction and Building Materials, Elsevier Ltd., Vol.363, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2022.129817)
Abstract
Repairing corroded flexural-deficient reinforced concrete (RC) structures using a hybrid scheme with stainless steel (SS) rebars and carbon-fiber-reinforced polymer (CFRP) sheets revealed excellent structural performance and contributes to lower maintenance costs in the remaining service life of the repaired structure. However, although cutting the bottom arm of stirrups in a hybrid repair method could affect the structural performance of shear-critical RC beams since this effect was not investigated in the past research. In this paper, structural performance of a group of shear-deficient RC beams repaired using the hybrid method is investigated experimentally to examine the effect of cutting the bottom arm of stirrup on the shear capacity of the repaired beams. The test variables included the longitudinal reinforcement types (i.e. carbon and SS), shear reinforcement configurations, and CFRP sheet wrapping schemes. Experimental results demonstrate that cutting the bottom arm of stirrup for replacing the corroded tensile rebar could significantly reduce the shear capacity of the retrofitted beams. Therefore, strengthening using CFRP sheet is needed to restore the shear performance of the retrofitted beams. Test results revealed that complete wrapping of CFRP sheet is effective to overcome the shear deficiency due to cutting the bottom arm of stirrup in the shear-critical RC beams. In addition, the effectiveness of CFRP sheet wrapping schemes on shear performance of SS-RC beams is approximately identical with that of CS-RC beams. Finally, a design methodology to repair the corroded RC bridge using hybrid method is developed and presented based on bending and shear tests. c 2022 Elsevier Ltd
Sonic-IR imaging technique for detection of crack interfaces in cementitious materials
Hashimoto K.; Shiotani T.
Construction and Building Materials, Elsevier Ltd., Vol.386, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2023.131549)
Abstract
Sonic-IR (Infrared) imaging technique was applied to detect defects of cementitious materials in the temperature rise of thermal imaging by ultrasonic excitation and infrared thermography on the target surface. It was investigated in this study to identify the fracture regions with cracks inside mortar and quantifying the epoxy resin filling situation at repaired crack in concrete. As the results, it was found that sonic-IR imaging technique can be utilized for detecting the fracture area and the crack propagation zone, although it is known that the technique is usually introduced for metals or composite materials which have high thermal conductivity. In particular, the shear fracture surface formed due to compressive stress could be detected as well as X-ray CT imaging. It was also enabled to quantitatively clarify the fracture progress with damage degree of mortar subjected to the compression stress and the epoxy resin injected depth at the simulated crack in concrete. c 2023 Elsevier Ltd
Insight on the mechanical properties of hierarchical porous calcium-silicate-hydrate pastes according to the Ca/Si molar ratio using in-situ synchrotron X-ray scattering and nanoindentation test
Im S.; Jee H.; Suh H.; Kanematsu M.; Morooka S.; Choe H.; Yuhei N.; Machida A.; Kim J.; Lim S.; Bae S.
Construction and Building Materials, Elsevier Ltd., Vol.365, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2022.130034)
Abstract
Nanocrystalline calcium?silicate?hydrate (C-S-H) is a typical heterogeneous material with a multiscale structure spanning a wide length scale from angstrom to micrometer, and whose structure is determined by the Ca/Si ratio. In this study, we directly applied compressive loads on synthetic C-S-H pastes with Ca/Si ratios of 0.6?1.2 and investigated their mechanical properties using the elastic modulus calculated at three length scale levels (i.e., angstrom to nanometer, micrometer, and millimeter) via in-situ synchrotron X-ray scattering, nanoindentation tests, and strain gauges, respectively. Further, 29Si nuclear magnetic resonance spectroscopy was conducted on the C-S-H pastes to elucidate the alterations in the silicate polymerization. The experimental results confirmed the deformation behavior of the C-S-H paste with different Ca/Si ratios under external loading, which was demonstrated to be transferred from the surface of the pastes to particles owing to the presence of multiscale pores. c 2022
A study on evaluating supporting condition of railway track slab with impact acoustics and non-defective machine learning
Inaba K.; Tanigawa H.; Naito H.
Construction and Building Materials, Elsevier Ltd., Vol.373, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2023.130905)
Abstract
Slab tracks are main ballastless tracks used in the high-speed railway system in Japan (Shinkansen). The track slab is a reinforced or pre-stressed concrete component in the slab track. This component is important to support traffic loading stably. We need to maintain the supporting condition of track slabs sustainably in the future because it has been passed nearly 50 years since the earliest of slab tracks have laid. Therefore, we need non-destructive testing methods to evaluating this condition of track slabs. We have been focused on non-destructive testing with impact acoustics. In this study, we improve this non-destructive testing by experiments in the full-scale models, eigenvalue analysis and non-defective machine learning. We have obtained the conclusion in this study as below: (1) Characteristics of impact acoustics depend on hammering position. For example, In the case of hammering at near the corner, impact acoustics is larger and damping more slowly than the case of hammering the center of long side. (2) It is desirable to measure near the hammering point or distance from not more than around 3 times the thickness of a track slab. (3) Principal component analysis and Autoencoder are useful for evaluating supporting conditions of track slabs. Both methods can discriminate the supported area and the voided one with accuracy rates of 81.92 % and 79.51 %, respectively. c 2023 Elsevier Ltd
Effect of numerous small deformations caused by moderate earthquakes on shear performance of wooden walls
Inoue R.; Mori T.; Matsumoto S.
Construction and Building Materials, Elsevier Ltd., Vol.364, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2022.130016)
Abstract
To confirm how repeated small deformations caused by moderate earthquakes during the use period of a wooden house affect the shear resisting wall, in-plane shear experiments with numerous small deformations on walls using plywood, gypsum board, and wooden braces were conducted. Even with small deformations, it was found that the load decreased, and the equivalent stiffness decreased because of the repetition of the same deformation for plywood and gypsum board wall. At 200 times repetitions of 1/450 rad, the load decreased to about 85 % for the plywood wall and 70 % for the gypsum board wall. The load reduction due to repeated deformation of gypsum board wall was larger than that of other walls. However, the characteristic values were not significantly affected, even if the wall received repeated small deformations. c 2022 Elsevier Ltd
Characterization of microstructures and micromechanical properties of naturally generated rust layer in 60-year old reinforced concrete
Jiang B.; Doi K.; Tsuchiya K.
Construction and Building Materials, Elsevier Ltd., Vol.366, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2022.130203)
Abstract
The mechanical properties of steel corrosion products reported in the literature present a great dispersion. The present study aims to explore the mechanical behavior of naturally generated corrosion products at the microscale level in relation with typical microstructural features. Microstructural characterization was performed on corrosion products by nano-indentation, Raman micro-spectrometry, scanning electron microscopy and electron backscatter diffraction. The Young's modulus and nanohardness range between 66.5 and 158.1 GPa and 2.97?11.71 GPa, respectively. The various morphologies and corresponding mechanical properties of goethite, maghemite and magnetite have finally been discussed, clarifying the influences of porosity, crystallinity and grain size on the mechanical properties. c 2022 Elsevier Ltd
Chloride diffusion along the interface between concrete matrix and repair materials under flexural loading
Li G.; Zhou Q.; Wang W.; Lu C.; Chen C.; Guo Z.; Lu C.
Construction and Building Materials, Elsevier Ltd., Vol.372, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2023.130829)
Abstract
The interface will be the weakest part after the rehabilitation of old concrete substrate; however, the durability of the interface has been unclear. To fill this gap, this study designed three typical interfaces to simulate those in field projects, i.e., the concrete-repair concrete interface, the concrete-repair cementitious grout interface, and the concrete-repair cementitious grout interface under flexural loading. An improved salt ponding test and a self-designed loading device for simulating the chloride contamination environment coupled with the loading were proposed. Results showed that as the water to cement ratio (w/c) of concrete decreased, the difference in chloride profile was also reduced in each part of the repair system, which presented no obvious difference when the w/c was 0.4. The chloride ion concentration was distributed in an asymmetric inverted V shape in all cases along the perpendicular direction of the interface. Besides, the influenced area of crack at the interface in the prefabricated concrete substrate was 10?20 mm, while that in the cast-in-place concrete substrate was 5?10 mm, along the direction perpendicular to the interface. The crack widths between 0.08 and 0.11 mm posed no great threat to the chloride diffusion at the interface under flexural loads. The present study suggests that the interface is the weakest part, for both mechanical properties and durability of a repaired concrete system. A novel model was proposed to describe the in-depth mechanisms based on complicated microstructure characteristics and particle?particle interactions at the interface. c 2023 Elsevier Ltd
Corrigendum to gNumerical method for thixotropic behavior of fresh concreteh [Constr. Build. Mater. 187 (2018) 931?941, (S0950061818318725), (10.1016/j.conbuildmat.2018.07.201)]
Li Z.; Cao G.; Guo K.
Construction and Building Materials, Elsevier Ltd., Vol.370, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2023.130689)
Abstract
The authors regret that Equation (12) in our paper was improperly edited: [Formula presented] Equation (12) should read: [Formula presented] We would like to confirm that all calculations conducted used the correct equation and that results published in the paper are correct. The authors would like to apologise for any inconvenience caused. c 2023 Elsevier Ltd
Experimental study on mortar with the addition of hydrophobic silicone oil for water absorption, strength, and shrinkage
Luan Y.; Asamoto S.
Construction and Building Materials, Elsevier Ltd., Vol.367, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2023.130323)
Abstract
In this study, a hydrophobic agent of silicone oil was used to treat mortar by directly mixing into the mixture and spraying it on the sand for pre-treatment, respectively, aiming to offer the mortar bulk water repellency that can be sustained even on the occurrence of cracking. Contact angle was measured for surface wettability, and water absorption and chloride penetration were tested on sound specimens that were pre-dried under two different conditions. Water absorption was further tested on the pre-cracked specimens to characterize water repellency with cracks. The mortar was also tested for compressive strength, Young's modulus, drying and autogenous shrinkage as well as setting times. The results indicated significant reduction of water absorption and chloride penetration with increasing addition and spraying amount of the agent than those of untreated mortar. Furthermore, for the pre-cracked specimens, water absorption was remarkably lower than that of untreated mortar, particularly under wetting/drying cycles, indicating that bulk water repellency can be preserved at a certain degree even if cracks occur. On the other side, the silicone oil reduced compressive strength and Young's modulus for both treatments. Autogenous shrinkage and drying shrinkage tended to decrease compared to untreated mortar. For direct mixing, the reduced drying shrinkage was partially attributed to its less water loss than that of untreated mortar, whereas for sand spraying, the weakened ITZ of the mortar was inferred to play a major role in reducing drying and autogenous shrinkage. c 2023 Elsevier Ltd
Development of machine learning methods to predict the compressive strength of fiber-reinforced self-compacting concrete and sensitivity analysis
Mai H.-V.T.; Nguyen M.H.; Ly H.-B.
Construction and Building Materials, Elsevier Ltd., Vol.367, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2023.130339)
Abstract
Fiber-reinforced self-compacting concrete (FRSCC), a great combination of self-compacting concrete (SCC) and fiber, plays a vital role as a potential construction material. Improving the accuracy of FRSCCf performance prediction methods is critical and challenging to reduce costly experiments and time. Therefore, this study developed and assessed the performance of three machine learning models, including Decision tree, Light Gradient Boosting Machine, and Extreme Gradient Boosting (XGBoost), for predicting the compressive strength (CS) of FRSCC. The models were developed based on 387 data samples with 17 input parameters. Monte Carlo and K-fold cross-validation techniques were used to assess the models' generalizability and predictive performance. The results showed that the XGBoost model has the highest predictive performance and stability, with typical results R2 = 0.992, RMSE = 1.892 MPa, MAE = 1.438 MPa. The sensitivity analysis of the models indicated that cement, coarse aggregate, fine aggregate, water, and sample age significantly influence the CS of FRSCC with inconsistent order. Finally, XGBoost was the most accurate and reliable model based on the final architecture analysis. c 2023 Elsevier Ltd
Toward improved prediction of recycled brick aggregate concrete compressive strength by designing ensemble machine learning models
Mai H.-V.T.; Nguyen M.H.; Trinh S.H.; Ly H.-B.
Construction and Building Materials, Elsevier Ltd., Vol.369, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2023.130613)
Abstract
The utilization of recycled brick aggregate concrete (RBC) is an area of active research, in which further investigation is needed to develop accurate models for predicting the behavior of RBC to ensure its safe and sustainable use in construction. This study presents an effective way to determine RBC's compressive strength (CS) based on an appropriate design of ensemble machine learning (ML) models, namely Gradient Boosting, Light Gradient boosting, AdaBoost, Extreme Gradient Boosting, Stacking, and Voting. A database covering 393 test results is compiled from the relevant literature for training and testing the models. In addition, 10-fold cross-validation and random splitting of data are used to ensure the reliability of predictions, as well as prevent overfitting. The findings reveal that the Stacking model has the greatest predictive ability, with a coefficient of determination of 0.95, root mean square error of 2.74 MPa, mean absolute error of 2.09 MPa, mean absolute percentage error of 0.10 on the testing dataset. In addition, Feature importance and Partial dependence plots analysis are utilized to investigate the impact of each RBC component on its CS. In RBC's mixed-component design, the outcomes of this research, along with a developed Graphical User Interface (GUI) for the CS, might be of great use to material engineers. c 2023 Elsevier Ltd
Investigating the fracture behavior of structural concrete shear key in prefabricated walls by discrete modeling
Mehrpay S.; Matsumoto K.; Zhu M.; Wang Z.; Ueda T.
Construction and Building Materials, Elsevier Ltd., Vol.397, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2023.132272)
Abstract
In this study, the cracking behavior of concrete-like materials in keyed shear joints of a structural member under the push-off test is investigated by employing discrete and continuum models. Initially, the behavior of the reinforced concrete member is simulated by a novel discrete element previously developed by the authors and referred to as the Rigid Body Coupled Spring model (RBCS). Shear key connections with different failure modes are modeled and compared to experimental observations. Following that, the numerical outcomes are discussed and compared with the outcome of Finite Element Method (FEM) models employing a continuum plasticity-based damage model. According to the obtained results, with the applied continuum method and constitutive model, unlike the experimental evidence, the modification of the shear key design did not have a significant effect on the failure mode of the modeled connection. On the other hand, the employed discrete element technique was able to represent the failure modes of the shear key connections. This study demonstrates the possibility of the application of discrete methods in studying the behavior of concrete in structural elements. c 2023 Elsevier Ltd
Appropriate geometrical factors for four-probe method to evaluate electrical resistivity of concrete specimens
Minagawa H.; Miyamoto S.; Kurashige I.; Hisada M.
Construction and Building Materials, Elsevier Ltd., Vol.374, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2023.130784)
Abstract
This study computes appropriate geometrical factors for the four-probe method to accurately evaluate the electrical resistivity of concrete specimens. The geometrical factors were obtained using the potential and current distributions in the specimens calculated by finite element method analyses adopting the Laplace equation, assuming a probe spacing of 1?9 cm for several types of specimens. Furthermore, a thorough discussion of the current distribution and the variation in the measurement results indicated that the probe spacing must be as wide as possible to evaluate the mean value of the electrical resistivity. c 2023 The Author(s)
Effect of limestone and granite stone powder on properties of cement-treated clay composites and their socioeconomic and environmental impacts
Nakayenga J.; Inui M.; Guharay A.; Hata T.
Construction and Building Materials, Elsevier Ltd., Vol.393, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2023.132064)
Abstract
Large volumes of stone powder, i.e., limestone and granite waste are produced annually. When reused in cement-treated clay, the granite stone powder particle size affected the composites' unconfined compressive strength (UCS). However, limestone's effect on cement-treated clay has yet to be addressed comprehensively. This paper presents the effects of uncalcined limestone of different sizes on the particle size distribution, consistency indices, and the UCS of cement-treated clay composites at curing periods of 1, 3, 7, and 28 days. A comparison between the performance of cement-treated clay-limestone, cement-treated clay-granite powder composites, and cement-treated clay and their effect on sustainable construction is also presented. After 1 and 3 days of curing, the UCS of cement-treated clay-limestone composites was higher than the cement-treated clay control sample. However, at 7 and 28 days, the cement-treated clay-limestone composites possessed similar UCS to the cement-treated clay control sample regardless of their particle size. Cement-treated clay-granite powder composites are stronger than cement-treated clay-limestone composites. Regardless of the performance differences, both limestone and granite powder can be reused in cement-treated clay without significant loss in UCS and provide environmental benefits such as reduced cement usage and embodied airborne emissions, energy, and abiotic depletion, among other factors. c 2023 Elsevier Ltd
New insights into restrained stress and deformation mechanisms of concretes blended with calcium sulfoaluminate and MgO expansive additives using multi-scale techniques
Ou G.; Kishi T.; Mo L.; Lin Z.
Construction and Building Materials, Elsevier Ltd., Vol.371, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2023.130737)
Abstract
The early-age cracking performance of expansive concrete relies heavily on the temperature, restraint and curing conditions. Empirical methods to use expansive additives are not always reliable in diverse engineering conditions. By using a novel approach with the self-developed temperature stress testing machine (TSTM), this study evaluates the early-age cracking sensitivity of concretes blended with Calcium Sulfoaluminate and MgO expansive additives under different engineering conditions. Their performances under wetting?drying cycles are also compared. To interpret the deformation mechanism in a microscopic scale, pore structures are characterized by mercury intrusion porosimetry and nitrogen adsorption/desorption tests. It is found that MgO concrete with proper reaction activity can offer more effective shrinkage-compensation effect than CSA concretes under high temperature or drying condition, due to its less demand for hydration water, delayed expansion and finer pore structure. The findings in this study offer us new insights in modelling and application of expansive concretes on site. c 2023 Elsevier Ltd
The influence of basalt fiber filament length on shear strength development of chemically stabilized soils for ground improvement
Owino A.O.; Hossain Z.
Construction and Building Materials, Elsevier Ltd., Vol.374, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2023.130930)
Abstract
In recent years, adding fiber reinforcements into chemically stabilized weak soils to resolve brittleness at the post-peak shear strength state is becoming an increasingly popular research area. However, there is little to no research investigating the shear developments initiated through the hybridization of ground improvement techniques using high-strength basalt fibers and sustainable chemical stabilizers such as rice husk ash (RHA). This study investigated how different basalt fiber filament lengths can reinforce and consequently influence shear response in such chemically stabilized soils. A series of triaxial compression tests, scanning electron microscopy (SEM), and X-ray powder diffraction (XRD), considering curing periods, were carried out on fiber-reinforced and unreinforced chemically stabilized specimens containing: weak clay soil, varied lengths of basalt fibers filaments, RHA, and cement in their specified combinations. Based on the results, an increment in basalt fiber filaments length significantly increased the deviatoric stresses, increasing cohesion and angle of internal friction by 81% and 63%, respectively. SEM imagery showed a highly reinforced soil composite at the microstructural level. At the same time, XRD analysis justified the presence of solid calcium aluminosilicate hydrate bonds, a product of pozzolanic activity. The fiber reinforcing mechanism through interfacial contacts between basalt fiber filaments and the new stabilized soil composite was investigated and validated to form a new construction material for use as a base course during ground improvement. c 2023 Elsevier Ltd
Experimental study on time-dependent DC resistivity of cement-based material considering microstructure and ion concentration
Peng Y.; Gong F.; Wang Z.; Zhao Y.; Jin W.; Meng T.; Maekawa K.
Construction and Building Materials, Elsevier Ltd., Vol.363, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2022.129830)
Abstract
This study aims to investigate the time-dependent direct current (DC) resistivity of cement-based materials considering various influential factors. Results show that a decreasing water-cement ratio, saturation degree, ion concentration and applied voltage, or an increasing curing age and amount of aggregate will lead to an increasing resistivity. In addition, it is found that the changing DC resistivity mainly results from the migration of conductive ions. Finally, the DC resistivity model proposed in the research has an accuracy of error less than } 10 %. c 2022 The Authors
Direct synthesis of construction material from low-quality sand reacted with KOH and ethanol
Qiu P.; Sakai Y.; Tamura Y.; Ogiwara N.; Uchida S.
Construction and Building Materials, Elsevier Ltd., Vol.392, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2023.131906)
Abstract
A strong construction material was synthesised directly from low-quality sand (defined as the sand that particle size smaller than 250 ƒÊm) via the sol?gel method with ethanol as the solvent. Appropriate KOH content and ethanol concentration could improve the reaction degree and promote the compressive strength. The main results indicated that the specimen with 50 mass% KOH and 80 v/v% EtOH had the highest strength (>25 MPa) with the lowest porosity (5.79%). The high strength was attributed to microcline and tetraethoxysilane formation. Microcline was formed due to the dissolution and reorganization of Si-O-Si(Al) bonds in the raw sand, leading to a more homogenous structure and the decrease in the porosity. Formed tetraethoxysilane was a good consolidate, which could function as glue to further increase the strength. The carbon emission of the sand-based material in the construction phase was 233 kg CO2 eq/m2, which could be greatly reduced after reusing waste solution and utilizing waste heat. Therefore, a tough construction material was synthesised, which can partially substitute concrete, thus addressing the problem of insufficient concrete raw materials. c 2023 Elsevier Ltd
Evaluation of the water penetration depth in mortar using water indicator and hyperspectral imaging
Rath S.; Sakai Y.
Construction and Building Materials, Elsevier Ltd., Vol.380, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2023.131269)
Abstract
Water penetration is a potential cause of premature deterioration of reinforced concrete structures. The water indicator used for water detection cannot detect water penetration depths in samples containing high amount of blast furnace slag (BFS). Hence, hyperspectral imaging (HSI) was introduced in this study. Mortar specimens with different water-to-binder (w/b) ratios and BFS replacements were prepared. The moisture content distribution, water indicator, and HSI were used to measure the water penetration depth in the samples after water absorption exposure. The effects of the pore size and moisture content on the mechanisms of the water indicator were also investigated. HSI successfully detected the penetration depth of water in all mortar samples, even in those where detection by using the water indicator was not possible. The moisture content distribution and HSI yielded similar results for water penetration depths. The water penetration depths measured by applying the water indicator and HSI were similar in the mortars without BFS substitution. The water indicator underestimated the water penetration depths in the samples that contained BFS. The amount free water in the pores of mortar was the main factor controlling the applicability of the water indicator. c 2023 Elsevier Ltd
Recycling and conservation of calcium carbide slag in dispersive soil modification: An evaluation of early age performance
Ren G.; Fan H.; Gao Y.; Guo H.; Wu T.; Zhao G.; Zhu Z.; Li X.; Chun P.-J.
Construction and Building Materials, Elsevier Ltd., Vol.393, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2023.132079)
Abstract
The disposal of calcium carbide slag (CCS) is still a serious problem for areas that rely on the polyvinyl chloride industry, especially in the northern part of China. To assess the early effectiveness of CCS in treating dispersive soil, mechanical, chemical, and microscopic tests were conducted. The pH and conductivity EC were also measured to evaluate the effect of active ions. Validation test was also conducted on a natural dispersive soil from northern Shaanxi to prove the improving effectiveness of CCS on the dispersivity of soil. Results showed that adding 2% CCS significantly limits the dispersivity of the soil and improves its resistance to water erosion and mechanical properties. Increases of 11 times and 4.8 times were observed when CCS content increased from 0% to 5% and curing time increased from 0 to 28 days for compressive and tensile strength, respectively. The correlation between dispersivity and mechanical properties with pH and EC during curing was found to be significant. This relationship is closely linked to the dissolution and consumption behavior of the active ions that are abundant and contributed by the functional oxides in the CCS. Microscopic tests indicated that the porous particle structure of CCS improves the mechanical properties and limits the dispersivity of soil, due to physical strengthening and carbonization reaction in the early stage of CCS application. The subsequent release of Ca2+ and the formation of C-S-H/C-A-H cementitious hydrates played a vital role in controlling chemical dispersivity and further improving the mechanical properties of the dispersive soil. This was accomplished through ion replacement and pozzolanic reactions that were supported by the abundant active ions. Validation test show that CCS could efficiently improve the engineering properties of dispersive soil and the recommended mixture ratio is 2?5%. c 2023 Elsevier Ltd
Shape optimization of Hourglass-shaped damper using Fe-Mn-Si-Based alloy considering target Load-displacement relationship and target fatigue characteristics
Suzuki T.; Motomura S.; Kinoshita T.; Inoue Y.; Kushibe A.; Iida T.
Construction and Building Materials, Elsevier Ltd., Vol.366, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2022.130091)
Abstract
To reduce the response of buildings during earthquakes, the use of various hysteresis dampers for passive control is increasing. For effective application to buildings, these dampers must meet both load displacement relationship and fatigue property requirements. In this study, shape optimization of an Fe-Mn-Si-based alloy damper was conducted to improve the fatigue property while maintaining the target load displacement relationship, and the obtained optimized damper was examined. First, shape optimization was conducted using the modal iterative error correction (MIEC) inverse analysis method. Subsequently, a loading test on the damper fabricated based on the optimized shape was conducted, and its effectiveness was confirmed. As a result, it was confirmed that the optimized shape of the damper, which improves the fatigue performance while maintaining the load displacement relationship, was successfully searched using the MIEC inverse analysis method. In addition, it was confirmed that the fatigue performance of the test specimen based on the optimized shape was improved compared to that of the initial-shape. c 2022 The Authors
Durability enhancement mechanism of mortar using blast furnace slag fine aggregate against combined deterioration of frost and salt damage
Ta Y.; Minagawa H.; Takahashi H.; Takahashi K.; Miyamoto S.; Hisada M.
Construction and Building Materials, Elsevier Ltd., Vol.367, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2022.130237)
Abstract
The effect of BFS (Blast Furnace Slag Fine Aggregate) on the freezing and thawing resistance under chloride environment was evaluated, and the freezing and thawing resistance was proven to be improved by using BFS with fine grain size and by increasing the mixing ratio of BFS to natural sand. The electrical resistivity and effective chloride ion diffusion coefficient were measured in order to evaluate the effect of BFS on the resistance of the penetration of chloride ions into concrete, and the mortar using BFS had higher electrical resistivity and lower effective chloride ion diffusion coefficient than the mortar using mountain sand. In order to elucidate the reaction products at the interface between cement paste and BFS, which cause densification of the BFS interface when BFS is used as fine aggregate in concrete, an investigation and analysis of the reaction products were conducted using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). As a result, it was found that a reaction phase is formed in the BFS-cement paste interfacial transition zone (ITZ), and its thickness is 0.45 to 1.4 ƒÊm. TEM observation and selected-area diffraction (SAD) analysis revealed the existence of hydrotalcite-like compounds in the BFS-cement paste ITZ. The chloride enrichment in hydrotalcite-like compounds at ITZ was confirmed by TEM observation and TEM-EDS of mortar with BFS after freeze?thaw tests under chloride environment. Therefore, it was considered to contribute to the improvement of the resistance of the penetration of chloride ions into concrete mixed with BFS. c 2022 The Author(s)
Evaluation of transport properties of deteriorated concrete due to calcium leaching with coupled CT image analysis and random walk simulation
Tan Y.; Sugiyama T.; Hashimoto K.
Construction and Building Materials, Elsevier Ltd., Vol.369, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2023.130526)
Abstract
Concrete may deteriorate when chronically in contact with water due to the leaching of calcium ions. This study conducted a natural diffusion test for calcium ions with a minute cylindrical specimen of 3 mm in diameter and 6 mm in height to determine leaching at 20 and 80 ‹C in 33 days. One piece of limestone as aggregate was inserted inside each specimen to investigate the effect of the interfacial transition zone (ITZ). Changes in mass transfer in the leaching and non-leaching regions in bulk cement paste were evaluated using synchrotron X-ray computed tomography (CT) in a micrometer order. A deeper dissolution front of Ca(OH)2 inside the specimen was observed for a higher temperature leaching test. Random walk simulation was performed to obtain diffusion parameters. Results showed that the calcium diffusion coefficient of non-deteriorated ITZ is about ten times as high as that of the non-leaching region. For the leaching region, the diffusion coefficient is about 50 times and 100 times as high as that of the non-leaching region at 20 ‹C and 80 ‹C, respectively. In addition, the Ca(OH)2 dissolution front appeared deeper inside the specimen in the direction where aggregate is close or exposed to the dissolution front because of ITZ. c 2023 Elsevier Ltd
Estimation of actual pore-size distribution by inverse analysis of mercury intrusion
Tanaka S.; Sakai Y.
Construction and Building Materials, Elsevier Ltd., Vol.366, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2022.130208)
Abstract
Intrusion curves under mercury intrusion porosimetry (MIP) severely underestimate pore sizes below the actual pore-size distribution (APSD), owing to the ink-bottle effect, producing difficulties in interpreting the dominant pore structure in various performances of concrete. This study proposes a method to estimate APSD from a MIP intrusion curve for understanding the pore structure accurately and easily. A model for calculating the volume of the ink-bottle pores was derived and incorporated into the inverse analysis system to obtain the APSD through a three-dimensional intrusion simulation. The APSD estimation results of the proposed and existing methods agreed well. c 2022 Elsevier Ltd
Production of green, low-cost and high-performance anorthite-based ceramics from reduced copper slag
Xu L.; Liu Y.; Chen M.; Wang N.; Chen H.; Liu L.
Construction and Building Materials, Elsevier Ltd., Vol.375, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2023.130982)
Abstract
Waste slags are promising sources of ceramic materials, but slag-derived ceramics also show inferior whiteness and quite different constituents compared to commercial products due to the introduction of impurity elements. To solve this issue, in this work, reduced copper slag after iron and copper extraction was used as a new raw material to prepare novel anorthite-based ceramics. The role of slag addition in the sintering, microstructure, physical and mechanical properties, leaching behavior, and color quality was investigated by using different characterization techniques such as DSC-TG, XRD, SEM, spectrophotometer, Archimedes method, 3-point bending method, and acetic acid buffer solution method. The results show that the ceramics are more effective in liquid generation with the slag addition, significantly enhancing the sintering and reducing the porosity. The slag also favors the development of anorthite grains as it is an Al2O3-SiO2-CaO-based system. As a result, a dense and well-bonded structure with few impurity phases and fine rounded pores is produced with 40 wt% of slag addition. These effects contribute to a remarkable improvement in flexural strength (87.6 MPa) and good maintenance of whiteness (?90). Moreover, its leaching toxicity is ? 3 orders of magnitude lower than the thresholds. The high strength, appearance quality and cleanliness are the competitive advantages of the designed ceramics compared to other slag-derived ceramics. However, limited densification and severe blisters and bloating appear after introducing more than 50 wt% of slag, leading to a much inferior mechanical and color performance. c 2023 Elsevier Ltd
Adding dry ice into ultra-high-performance concrete to enhance engineering performances and lower CO2 emissions
Xuan M.-Y.; Lee S.-H.; Hu H.-Q.; Wang X.-Y.
Construction and Building Materials, Elsevier Ltd., Vol.392, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2023.131858)
Abstract
Developing low-carbon cement-based materials is crucial to address the pressing sustainability concerns the construction industry faces. This study elucidates the effect of adding dry ice on the micro-meso-macro properties of ultra-high-performance concrete (UHPC). The main original points of the method were summarized as follows: simple operation, low technical difficulty, no specific equipment required, and solving the problem that the carbonation curing method is difficult to use in low water-cement ratio concrete. The results show that adding dry ice generates microscopic CO2 bubbles that react with the carbonation of Ca(OH)2 and improve the later-stage strength and electrical resistivity. And adding dry ice reduces the heat of hydration and promotes ettringite formation. The results of microscopic analyses confirmed that increasing the dry ice content results in a decrease in Ca(OH)2; hence more calcium carbonate is formed. It was also observed that the carbon conversion effect became more apparent when the curing period was 28 days. And optical micrograph analysis showed that adding dry ice increased the total bubble content of the matrix and decreased the average bubble diameter, thus affecting the change in macroscopic properties. Moreover, as the addition of dry ice increased from 0 to 15%, the CO2 emission per unit strength decreased from 6.5 to 4.5 kgECO2Em?3EMPa?1 (30% reduction in CO2 emission). Therefore, adding dry ice to UHPC is an effective way to utilize carbon and is crucial to achieving carbon neutrality in the concrete industry. c 2023
Influence of chloride solutions on the leaching of heavy metals from cement hydrates
Zhou S.; Ogawa Y.; Kawai K.
Construction and Building Materials, Elsevier Ltd., Vol.378, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2023.131108)
Abstract
This study investigates how chloride-based salts affect the immobilization and leaching of Cu, Zn, and Pb from cement hydrates and analyzes the associated internal changes in crystalline phase. Results showed that the amount of Pb leached is highest in mortar when it contacts with CaCl2 solution. A key reason for this outcome is that calcium silicate hydrate (CSH) has the lowest Pb adsorption in CaCl2 solution. Exposure to MgCl2 solution resulted in the decomposition of most portlandite to form brucite in mortars, lowering the pH to ?9. This caused the lowest leaching rate of Cu, Zn, and Pb in MgCl2 solution. c 2023 Elsevier Ltd
Bond performance of carbon fiber reinforced polymer rebars in ultra-high-performance concrete
Zhu H.; He Y.; Cai G.; Cheng S.; Zhang Y.; Si Larbi A.
Construction and Building Materials, Elsevier Ltd., Vol.387, 2023, .
(https://doi.org/10.1016/j.conbuildmat.2023.131646)
Abstract
This paper investigated the bond performance between carbon fiber reinforced polymer (CFRP) bars and ultra-high-performance concrete (UHPC) by a hinged beam test investigation. A total of 11 sets of beam tests were carried out to investigate the effect of different parameters on the bond performance, including steel fiber volume fraction, bonded length, reinforcement diameter, and concrete cover. The tests showed that the bond damage modes between CFRP bars and UHPC were dominated by pull-out damage, with the surface of the bonded section of CFRP bars being peeled off from the internal core and no damage observed in the UHPCs. An increase in the cover and steel fiber volume fraction improves the bonding performance, while an increase in diameter reduces the bond performance. Based on this study, the formulae for calculating the ultimate bond strength and development length that integrated the effects of CFRP bar diameter, bonded length, and cover thickness were proposed. The bond-slip curve shows three stages, i.e., ascending section, descending section, and a residual section showing periodic fluctuations. The fluctuation period showed a certain degree of linear correlation with the rib spacing of CFRP bars. Based on the characteristics of tested curves, a bond-slip constitutive model was proposed to simulate the bond-slip behavior of CFRP bars in UHPCs with good agreement to test results. c 2023 Elsevier Ltd
Investigation of premature failure mechanism in pavement overlay of national highway of Bangladesh
Abadin M.J.; Hayano K.
Construction and Building Materials, Elsevier Ltd., Vol.318, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2021.126194)
Abstract
Roadway is the economic lifeline of Bangladesh. Maintenance of this roadway is main challenge of Roads and Highways Department (RHD). Overlay is the most common maintenance practice for National Highways, which design life is five years. However, it's been reported, the overlay failed prematurely with cracking and rutting within one year even 6 to 9 months in some cases. This study aiming to investigate the premature failure mechanism of national highway pavement. Several field investigations were done on national highway namely N2. A numerical parametric study was also conducted with variable interfacial bond condition, overloading and layers stiffness. To investigate the pavements failures, conventional fatigue and rutting criteria were considered. Laser crack measurement system showed that alligator cracking is dominant failure mode followed by rutting. Alligator crack pattern indicated about slippage failure and overloading induced fatigue failure. Core cutting confirmed that interface de-bonding and cracking are strongly related. Bitumen samples were found highly temperature susceptible which could be correlated slippage failure. Moreover, Base layer stiffness variation was observed from Dynamic Cone Penetration test. Numerical analysis revealed that poor interfacial bonding significantly affects horizontal and vertical strain distributions; subsequently reduce pavement life but only it is not enough to fatigue and rutting failure of N2 within one year. Overloading found more significant than de-bonding especially for rutting. Analysis also suggested that fatigue and rutting failure within one year should be associated by coupling effect of poor bonding and overloading. Variation of base layer stiffness might be exacerbated the coupling effect in N2. c 2021 Elsevier Ltd
Material comparative analysis of crack-bridging degradation of SFRC structural beams under flexural fatigue loading
Adel M.; Matsumoto K.; Ueda T.; Nagai K.
Construction and Building Materials, Elsevier Ltd., Vol.339, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.127642)
Abstract
This study experimentally investigates the influence of several material parameters on steel fiber reinforced concrete (SFRC) structural beams and their crack-bridging degradation over constant and variable amplitudes of flexural cyclic loading. Crack-bridging stress is evaluated using inverse analysis and its degradation against maximum rebars strain is derived. Four series of SRFC beams are prepared and characterized with different concrete compressive strengths, hooked-end steel fiber shapes in two different volume fractions, and two longitudinal reinforcement ratios. The results reveal lower crack-bridging degradation rates, and associated longer fatigue life and higher residual capacity, for beams with higher concrete strength. Further, SFRC fracture energy is shown to have a significant effect on fatigue response, with higher fracture energy associated with lower rates of crack-bridging degradation. However, steel fibers with double hooks are shown to have a relatively insignificant effect on controlling crack-bridging degradation rates and the flexural cyclic responses of SFRC beams as compared to single hook fibers. Also demonstrated is that a lower longitudinal reinforcement ratio leads to higher rebar strain rates with no influence on crack-bridging stress. Crack-bridging degradation diagrams are proposed for SFRC beams that quantitatively capture several material parameters effects based on their mechanical properties over the fatigue life. c 2022 Elsevier Ltd
3D mesoscale simulation of the influence of corrosion on loss of tension stiffening in reinforced concrete
Avadh K.; Jiradilok P.; Bolander J.E.; Nagai K.
Construction and Building Materials, Elsevier Ltd., Vol.339, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.127684)
Abstract
Corrosion-induced bond degradation leads to changes in deformation characteristics, cracking patterns, and loss in tension stiffening in structural members. Since the induced damage is dependent upon multiple inter-related parameters, prediction of post-corrosion deformation behavior requires sophisticated numerical simulations. This study integrates corrosion expansion and bond degradation models into a discrete analysis framework, 3D RBSM (Rigid Body Spring Model), to simulate post-corrosion loss of tension stiffening. Uniaxial tensile loading is applied to reinforced concrete models with different degrees of corrosion to obtain plots of load versus average strain and surface cracking patterns. Simulated surface cracking patterns due to corrosion and uniaxial loading in uncorroded and corroded models are similar to experimental results. As the degree of corrosion increases, the number of transverse cracks on the concrete surface decrease and the load at first cracking also decreases. Further, internal stress and bond stress investigation directly illustrate the decrease in stress transfer from reinforcing bar to concrete due to corrosion. c 2022 Elsevier Ltd
Experimental analysis and numerical simulation of flow behavior of fresh steel fibre reinforced concrete in magnetic field
Cao G.; Li Z.; Jiang S.; Tan Y.; Li Z.; Long S.; Tong Z.
Construction and Building Materials, Elsevier Ltd., Vol.347, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.128505)
Abstract
Fluidity is an important index to describe the performance of fresh concrete, which has a great influence on the transportation and casting process of concrete. By applying a magnetic field to steel fibre reinforced concrete, in which steel fibre can be oriented to improve flow performance and strength. In this paper, the mechanical model of steel fibre in magnetic field was established in EDEM, and the simulations of magnetic field orientation as well as slump of steel fibre concrete were carried out and compared with the experiment. The errors between numerical and experimental results are less than 5%, which confirms the validity of the model. The effects of magnetic flux density and duration on the orientation of steel fibre and the effect of orientation on flow of mortar were analyzed. It was found that the larger the magnetic flux density, the better orientation of steel fibre. And regardless of the magnitude of magnetic flux density, most steel fibres can be oriented in a relatively short time. Due to the effect of gravity, orientation of mortar in the bottom is more difficult than that in the upper. The magnetic flux density, the initial position of the steel fibre and the resistance to the steel fibre affect the final orientation. When the magnetic field direction is horizontal, the fluidity of mortar along the magnetic field direction decreases with the increase of magnetic flux density, while the fluidity along the vertical magnetic field direction increases. The vertical magnetic field has no obvious effect on the fluidity. c 2022 Elsevier Ltd
Experimental and analytical studies on mechanical performance of innovative energy-dissipating hold-down for CLT structures
Chen J.; Xiong H.; Furuta T.; Lu Y.; Abbas N.
Construction and Building Materials, Elsevier Ltd., Vol.317, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2021.125966)
Abstract
Connection is the most important part in cross-laminated timber (CLT) buildings as it guarantees necessary strength, stiffness, ductility, and integrality for the whole CLT structure. This paper proposes an innovative energy-dissipating hold-down connection for CLT structures, which combines the advantages of the soft-steel bracket and high-damping rubber for providing great energy-dissipating capacity and high ductility. A series of tests were performed under quasi-static monotonic and reversed cyclic loading to investigate the failure mechanisms and mechanical properties of the novel hold-down connection. Test results demonstrate that the connections can continue to work as a whole even after the occurrence of preliminary failures of steel ribs rupture and weld fracture. Final failure modes, including debonding between the rubber and steel plates, rupture of the front steel plate and breakage of screws, caused the invalidation of the connection. Meanwhile, load?displacement curves of the connections usually exhibit a bi-linear form, and the connection's yielding is caused by the yielding of steel ribs. All the tested specimens exhibited stable energy-dissipating capacity in the working stage and were all classified as highly ductile. Furthermore, efforts were made to develop a simplified analytical model for estimating the basic mechanical properties of the novel hold-down connections. Comparison with test results shows that the analytical model can provide reasonable estimations of the initial stiffness, post-yield stiffness, yield force and failure force. The test results and analyses presented herein provide useful technical bases for supporting future studies and practical applications of the novel hold-down connection for CLT buildings. c 2021 Elsevier Ltd
Virtual mix design: Prediction of compressive strength of concrete with industrial wastes using deep data augmentation
Chen N.; Zhao S.; Gao Z.; Wang D.; Liu P.; Oeser M.; Hou Y.; Wang L.
Construction and Building Materials, Elsevier Ltd., Vol.323, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.126580)
Abstract
The adding of industrial wastes, including blast furnace slag and fly ash, to concrete materials will not only improve the working performance, but also significantly reduce the carbon emissions and promote the green development in civil engineering area. The traditional material designs are mainly indoor laboratory-based, which is complex and time-consuming. In this study, a virtual material design method, including deep data augmentation methods and deep learning methods, was employed to predict the compressive strength of concrete with industrial wastes. Three types of Generative Adversarial Networks (GANs) were employed to augment the original data and the results were evaluated. The test was conducted based on a small experiment dataset from previous literature, comparing with traditional machine learning methods. Test results show that the deep learning methods have the highest accuracy in compressive strength prediction, increasing from 0.90 to 0.98 (Visual Geometry Group, VGG) and from 0.83 to 0.96 (One-Dimensional Convolutional Neural Network, 1D CNN) after deep data augmentation, where the prediction accuracy of Random Forest (RF) and Support Vector Regressive (SVR) in traditional machine learning algorithms increase from 0.91 to 0.96 and from 0.78 to 0.86, respectively. In addition, a lightweight deep convolutional neural network was designed based on the augmented dataset. The results show that the lightweight model can improve the computation efficiency, reduce the complexity of the model compared with the original model, and reach a great prediction accuracy. The proposed study can facilitate the concrete material design with industrial wastes with less labor and time cost compared with traditional ones, thus can provide a cleaner solution for the whole industry. c 2022 Elsevier Ltd
Combined effect of rice husk ash and superabsorbent polymer on self-healing capability of mortar
Chindasiriphan P.; Yokota H.; Kawabata Y.; Pimpakan P.
Construction and Building Materials, Elsevier Ltd., Vol.338, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.127588)
Abstract
This paper deals with combined effect of rice husk ash (RHA) and superabsorbent polymer (SAP) on self-healing capability of mortar with cracks. RHA is commonly used in concrete as supplementary cementitious materials (SCMs). RHA, due to its silica-rich composition, is characterized by long-term strength enhancement that results from the pozzolanic reaction. However, RHA consumes large amount of portlandite, which is one of the sources of Ca for self-healing of cracks. Therefore, using RHA may result in less self-healing performance than other types of SCM, such as fly ash. SAP is used as a water-entraining admixture that supplies moisture to damaged parts of concrete and is used for self-healing material. Therefore, the combination of RHA and SAP potentially enhances the self-healing performance compared to the system only with RHA. From this context, this study investigates the potential for combination of RHA and SAP as self-healing additives. High-Ca fly ash is also used for comparison. Six mix proportions of cement mortar were developed, with the mortar set to almost uniform flowability. Pre-cracked specimens were healed either by continuous water immersion or by exposure to wet?dry conditions. Self-healing performance was evaluated by the following: permeability recovery (i.e., permeability reduction), as monitored by temporal decreases in water discharge through a crack. As the results, the RHA-based system turned out to have lower self-healing performance in terms of crack closure than fly ash-based system. This is because portlandite is the main source of Ca-based healing products, and less portlandite was found to be available in the RHA-based systems than in the FA-based systems. On the other hand, the self-healing performance of RHA-based systems was effectively improved with combination with SAP. c 2022 Elsevier Ltd
Prediction of interlayer shear strength of double-layer asphalt using novel hybrid artificial intelligence models of ANFIS and metaheuristic optimizations
Dao D.V.; Bui Q.-A.T.; Nguyen D.D.; Prakash I.; Trinh S.H.; Pham B.T.
Construction and Building Materials, Elsevier Ltd., Vol.323, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.126595)
Abstract
The pavement damages such as slipping, rutting, top-down cracking of flexible pavement are very common during the operation process. These damages are mainly caused by interlayer shear stress acting between the asphalt layers during traffic movement. This is one of the main reasons for reduced pavement service life and increased maintenance costs. Therefore, the Interlayer Shear Strength (ISS) parameter needs to be evaluated and accurately predicted. Generally, ISS of double?layer asphalt concrete is measured directly in the field or on the samples in the laboratory, which involves much time and cost. Therefore, in this study, we have estimated ISS of asphalt pavement based on three input parameters: temperature, normal pressure and aggregate diameter using novel hybrid machine learning models namely Culture Algorithm based Adaptive Neuro Fuzzy Inference System (ANFIS-CA), Differential Evolution based Adaptive Neuro Fuzzy Inference System (ANFIS-DE) and Invasive Weed Optimization based Adaptive Neuro Fuzzy Inference System (ANFIS-IWO). Estimated shear strength was compared with the direct measured shear strength for the validation of model's performance. In this study results of 180 double-layer asphalt samples which were fabricated by three different mixtures of Dmax 12.5, Dmax 19 and Dmax 25 and tested by shear device in the laboratory with five levels of normal pressure (0, 0.14, 0.2, 0.4, 0.6 MPa) at three temperature levels (25, 40 and 60 ‹C) were considered. Standard statistical measures namely Mean Absolute Error (MAE), Root-Mean-Square Error (RMSE), and Correlation Coefficient (R) were used to assess the modelsf prediction capabilities. The results exhibit that all the suggested models have high accuracy of prediction, but performance of ANFIS-IWO (MSE = 0.02, MAE = 0.024, RMSE = 0.047, and R = 0.953) is slightly better than ANFIS-CA (MSE = 0.04, MAE = 0.031, RMSE = 0.047, and R = 0.966) and ANFIS-DE (MSE = 0.03, MAE = 0.034, RMSE = 0.057, and R = 0.953). Therefore, all the proposed models are suitable and powerful potential tools for the accurate prediction of the ISS for the proper consideration of pre-construction and post-construction pavement asphalt mixture design but the ANFIS-IWO model is the best. c 2022 Elsevier Ltd
Stress reduction effects of ultra-high performance fiber reinforced concrete overlaid steel bridge deck developed with a new interfacial bond method
Deng P.; Mi H.; Mitamura H.; Matsumoto T.
Construction and Building Materials, Elsevier Ltd., Vol.328, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.127104)
Abstract
The effects of a 25 mm of UHPFRC overlay on reducing the stress of the open ribs-stiffened orthotropic steel decks (OSDs) are assessed experimentally and analytically. To integrate the UHPFRC overlay and the OSDs, an adhesive-based bonding technique is developed and evaluated beforehand using a pull-off test and a three-point bending test, where a 3 MPa of excellent bond strength and an invisible slip demonstrate the reliability of the technique. With the developed bonding technique, an up to 80% of strain reduction and a peak clipping phenomenon are observed in the strain of the critical locations of the steel deck and structural members in the hotspot areas due to the UHPFRC. In addition, it is found that the superior high strengths and the strain-hardening of UHPFRC can postpone the initiation and propagation of cracks. As a result, an effective enhancement of stiffness of OSDs and an apparent fatigue life extension can be achieved even with a thin layer. c 2022 Elsevier Ltd
Evaluations of frost and scaling resistance of fly ash concrete in terms of changes in water absorption and pore structure under the accelerated carbonation conditions
Ding Z.; Quy N.X.; Kim J.; Hama Y.
Construction and Building Materials, Elsevier Ltd., Vol.345, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.128273)
Abstract
In this study, the frost and scaling resistance of concrete with various fly ash (FA) replacement ratios exposure to air and accelerated carbonation conditions were investigated. The changes in water absorption were measured by RILEM / CIF test and in pore structure were measured by the Archimedes method and the mercury intrusion porosimetry method due to carbonation. Results show that the influence of FA and carbonation on the frost and scaling resistance of concrete can be ignored due to air bubbles by air entraining (AE) admixture in case of AE FA concrete. For Non-AE FA concrete, carbonation of FA concrete does not change the gel porosity/capillary porosity ratio, which is the reason for the frost resistance is not influenced by carbonation of FA concrete. Additionally, it is noteworthy to note that the scaling resistance is strongly connected to the pore volume above 75 nm, and that when exposed to carbonation, the scaling resistance tends to rise as a result of the increase in pore volume above 75 nm that occurs as a result of carbonation. Because of the addition of FA and carbonation, the frost and scaling resistance are far more reliant on the changes in pore structure than they are on the water absorption. c 2022 Elsevier Ltd
A study on the change in frost resistance and pore structure of concrete containing blast furnace slag under the carbonation conditions
Ding Z.; Quy N.X.; Noguchi T.; Kim J.; Hama Y.
Construction and Building Materials, Elsevier Ltd., Vol.331, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.127295)
Abstract
In this study, the change in frost resistance and pore structure of concrete containing blast furnace slag with various replacement ratio due to carbonation were investigated. As a result, there is a close relationship between the carbonation speed and 28-day compressive strength in blast furnace slag concrete. The frost resistance, carbonation resistance and scaling resistance of blast furnace slag cement concrete decrease as blast furnace slag replacement ratio increases. Furthermore, due to carbonation, the frost durability of ordinary Portland cement concrete and the concrete with a low replacement ratio of blast furnace slag tends to decrease. However, the concrete with a high replacement ratio of blast furnace slag tends to increase. Under the carbonation conditions, the pore volume decreases due to carbonation of calcium hydroxide, and the pore structure will be coarsened due to carbonation of C-S-H. In addition, it is expected that permeability of concrete is raised and scaling is inhibited due to carbonation, and the surface area with a certain thickness in the carbonated concrete will be scaled due to freeze?thaw. c 2022 Elsevier Ltd
Influence of hydrothermal synthesis conditions and carbonation on physical properties of xonotlite-based lightweight material
Duc Van N.; Imasawa K.; Hama Y.
Construction and Building Materials, Elsevier Ltd., Vol.321, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.126328)
Abstract
This paper investigates the effect of the hydrothermal synthesis conditions on the formation of xonotlite and the change of xonotlite-based lightweight material's (Xo_AAC) physical properties under carbonation. Experiments included: quantitative X-ray diffraction, scanning electron microscopy, thermogravimetric differential thermal analysis, drying shrinkage, carbonation shrinkage, compressive strength, mercury intrusion porosimetry, thermomechanical analysis, solid-state nuclear magnetic resonance, water vapor absorption isothermal, and nanoindentation test. The pure crystalline xonotlite was formed at 230 ‹C for the autoclaving time of more than 18 h and at short heating time (2 h). The drying shrinkage and dimensional change rate of Xo_AAC were smaller than that of autoclaved aerated concrete (AAC). The compressive strength of Xo_AAC was slightly increased after carbonation. The carbonation of Xo_AAC occurred more quickly than AAC containing silicone oil. However, the amount of carbonation shrinkage was almost the same for both Xo_AAC and AAC in a later period. c 2022 Elsevier Ltd
Expansion characteristics of concrete with free lime based expansive additives under uniaxial restraint conditions
Gupta M.; Pen K.; Igarashi G.; Takahashi Y.; Ishida T.
Construction and Building Materials, Elsevier Ltd., Vol.356, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.129330)
Abstract
Expansive additives in higher dosages induce chemical prestress in concrete by imparting higher early-age expansion. However, induced stress and concrete expansion can vary significantly, depending on different restraint conditions. In addition, concrete expansion can be highly anisotropic depending on the nature of external restraints and boundary conditions. Experimentations have been performed to study the effect of uniaxial (anisotropic) restraint on the concrete expansion (in both restraint and stress-free directions) and induced prestress. A higher degree of restraint resulted in a substantial decrement in the longitudinal expansion. In contrast, expansion in the stress-free (lateral) direction was not much affected by the restraint in other direction. As a result, an overall decrement in the volumetric expansion was observed with an increase in the reinforcement ratios. Stress induced in concrete due to the restraint expansion in the longitudinal direction was found to be higher for a higher reinforcement ratio. Data provided from the current work can be used for the comprehensive modelling of expansive concrete under external restraints. c 2022 Elsevier Ltd
Long-term corrosion resistance of Cu-Al-Mn superelastic alloys and steel rebar for use in bridges
Hong H.; Gencturk B.; Brown S.A.; Hosseini F.; Jain A.; Aryan H.; Saiidi S.; Araki Y.; Kise S.
Construction and Building Materials, Elsevier Ltd., Vol.350, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.128795)
Abstract
Cu-Al-Mn (CAM) superelastic alloys (SEAs) have been shown to improve the seismic performance of bridges and buildings by replacing the plastic hinge steel reinforcement. Despite research on mechanical performance at the material and structural scales, there is limited data on the degradation in the properties of CAM SEAs under harsh environmental conditions; particularly, under long-term corrosion that are relevant for civil engineering structures. This research aims to fill this knowledge gap by studying the long-term corrosion resistance of CAM SEAs in comparison with different types of steel reinforcing bars (rebar) used in construction. Long-term accelerated corrosion testing of CAM SEAs and four types of commonly used steel rebar, namely, mild steel (MS), high chromium steel (XS), epoxy coated steel (ES), and stainless steel (SS), was conducted up to 1,051 days. Three different diameters (U.S. #3, ƒ³ = 9.53 mm; U.S. #5, ƒ³ = 15.88 mm, and U.S. #10, ƒ³ = 32.26 mm) of steel rebar were considered to determine the effect of bar size on the corrosion rate. Mechanical tests were conducted after specimens reached predetermined corrosion levels. The critical mechanical properties of CAM SEAs and four steel rebar were extracted and analyzed. In addition, potentiodynamic polarization tests were performed and the Tafel curves were employed to determine the corrosion rates of CAM SEAs, steel rebar and NiTi SEAs. NiTi alloy was used as a reference for being the more traditional composition used as SEAs. It was found that the corrosion resistance of CAM SEAs is higher than MS and XS, but lower than NiTi SEA, SS and ES. The superelasticity, particularly the strain recovery, of CAM SEAs showed almost no degradation after over three years of corrosion. The experimental data and control groups in this research provide detailed evaluation of the corrosion resistance of CAM SEAs and guides the application of CAM SEAs in harsh environmental conditions. c 2022 Elsevier Ltd
Effect of thermal treatment on strengthening recycled compacted concrete incorporating iron, steel, and blast furnace slag
Ibrahim Mostazid M.; Medepalli S.; Sakai Y.
Construction and Building Materials, Elsevier Ltd., Vol.347, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.128623)
Abstract
High-pressure compaction recycling is a relatively recent method of manufacturing compact (recycled compacted concretes) from concrete wastes. Elevated-temperature treatment was found to be effective in producing normal strength compact (21 MPa); however, its strength and microstructural behavior has not yet been thoroughly investigated. This study investigates how thermal treatments (drying, high-temperature exposure, and autoclaving) affects the strengthening of compact based on microstructural analyses. Compact is prepared from the powder of ordinary concrete incorporating blast furnace slag and iron and steel slag as aggregate substituting materials. Microstructure analyses are conducted using mercury intrusion porosimetry, thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy. The test results reveal that thermal treatment induces a change in the microstructural configuration, thereby enhancing the compact strength. Reorientation of the interfacial transition zone, production of secondary hydrates, and pore refinement improve the compact strength. These effects are prominent when the aggregate substitution is 50 %. This article will assist in understanding strengthening mechanism and choosing an appropriate treatment environment to produce strong compact. c 2022 Elsevier Ltd
Hybrid biocomposites with high thermal and noise insulation from discarded wool, poultry feathers, and their blends
Ilangovan M.; Navada A.P.; Guna V.; Touchaleaume F.; Saulnier B.; Grohens Y.; Reddy N.
Construction and Building Materials, Elsevier Ltd., Vol.345, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.128324)
Abstract
Sheep wool and poultry feathers have unique properties that provide excellent noise and thermal insulation, and flame resistance when used as reinforcement for poly propylene. Discarded wool and poultry feathers are not only available in large quantities at low cost but have distinct characteristics that make them ideal to develop composites for various applications. In this study, we have studied the changes in tensile properties, thermal conductivity, sound absorption, and flame resistance of composites fabricated using wool and poultry feathers individually and as blends in various proportions. Reinforcing with sheep wool provided higher tensile and flexural strength compared to feathers. Compared to neat PP, higher tensile strength and modulus were obtained with 70% sheep wool as reinforcement but the flexural strength and modulus of the individual wool or feather and hybrid composites were considerably lower. When equal proportions of wool and feathers are used, the strength and modulus decreased compared to using the reinforcements individually. However, combining wool and feathers in 50/50 ratio and with 80% reinforcement, the composites had high sound absorption co-efficient of 0.55 with peak sound absorption found throughout the 1000 to 6000 Hz range depending on the proportion of wool and feathers. A flame resistance rating of V1 and thermal conductivity of 0.630 W/mK was obtained for the composites. Biocomposites with desirable properties could be obtained by blending sheep wool and poultry feathers for specific applications, particularly where acoustic, thermal and flame resistance is necessary. c 2022 Elsevier Ltd
Evaluation of single shear performance of nailed joint damaged by cyclic deformation due to moderate earthquakes
Inoue R.; Mori T.; Ariki A.; Matsumoto S.
Construction and Building Materials, Elsevier Ltd., Vol.342, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.128044)
Abstract
A single face shear experiment with numerous small deformations of the nailed joint was performed on plywood, OSB, MDF, and gypsum board to confirm whether cyclic deformations caused by moderate earthquakes affect the shear resisting wall of a wooden house. As a result, it was found that the maximum load and yield load are not significantly affected even when repeatedly small deformed. The reduction ratio of the load of gypsum boards was higher than that of other boards due to repeated deformation. Additionally, the equivalent stiffness of repeated specimens was reduced accordingly. It was supposed that the equivalent stiffness of the shear resisting wall decreases when it is repeatedly deformed. c 2022 Elsevier Ltd
Investigating the effect of rebar corrosion order and arrangement on cracking behaviour of RC panels using 3D discrete analysis
Joshi S.S.; Avadh K.; Singh Kuntal V.; Jiradilok P.; Nagai K.
Construction and Building Materials, Elsevier Ltd., Vol.325, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.126730)
Abstract
In real structures, corrosion cracking patterns tend to be complex as a result of congested rebar arrangements and non-uniform corrosion distribution. It is challenging to understand the internal corrosion cracking behaviour based only on the limited amount of visible surface cracks. The present study attempts to use a meso-scale discrete element method, the three-dimensional rigid body spring model (3D-RBSM), to simulate factors that affect corrosion cracking. Factors considered in reinforced concrete panels with multiple corroded rebar includes, corroded rebar location, corrosion order among rebars and rebar arrangement. Three different cases are simulated and the results are compared with previously published experimental results. In one set of simulations, the non-uniform rebar corrosion profiles obtained in the experiments are utilized, with the results showing similar cracking patterns to the experimental ones. In a second set of simulations, uniform corrosion is assumed so as to conduct a parametric study of the same specimens for an accurate understanding of each influencing factor. It is observed that when all rebars corrode simultaneously, the initial cracks propagate along the outer rebars because this is where the confinement effect is minimum. Cracking along inner rebars is delayed due to strong compression zone resulting from mechanical interaction among corroded rebar stresses. However, this compression zone is reduced when the rebars corrode in two stages and cracking occurs at all the rebar locations. Cracks that initially form along the inner rebars can close up when corrosion of the outer rebars occurs later. c 2022 Elsevier Ltd
Spark plasma sintering using calcareous waste concrete powder
Kanda Y.
Construction and Building Materials, Elsevier Ltd., Vol.349, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.128726)
Abstract
In this study, spark plasma sintering (SPS) was performed using calcareous waste concrete powder. In particular, we examined the sintering temperature for SPS. This improved the flexural strength and flexural modulus. Two types of calcareous waste concrete powders were prepared: waste mortar powder (WMP) and waste coarse aggregate powder (WCAP). The characteristics of the sintered bodies were evaluated using a three-point flexural test and powder X-ray diffraction (XRD). As the main crystalline component of the raw powder, WMP included calcite and quartz, and WCAP included calcite and hematite. Regarding the flexural strength of the sintered body, WMP had 52.6 MPa at a sintering temperature of 900 ‹C, and WCAP had 42.4 MPa at a sintering temperature of 850 ‹C. These values are higher than the value of 35 MPa of ISO 13,006 standard, which prescribes porcelain stoneware tiles. XRD analysis reveals the synthesis of spurrite, gehlenite, wollastonite, and larnite in WMP, and in WCAP, spurrite and magnetite are confirmed. The synthesis of these chemical compounds is attributed to the decarbonation reaction of calcite at 760 ‹C. Therefore, calcareous concrete can be used as a raw material for construction ceramics when applied to SPS. c 2022 Elsevier Ltd
Application of bio-based materials to crack and patch repair methods in concrete
Kawaai K.; Nishida T.; Saito A.; Hayashi T.
Construction and Building Materials, Elsevier Ltd., Vol.340, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.127718)
Abstract
This study explored the application of bio-based repair materials to concrete for crack repair and patch repair methods. First, the concept of crack repair using Bacillus subtilis (natto) under wet conditions is presented. In addition to the self-healing efficiency, enhancement of corrosion resistance owing to consumption of dissolved oxygen by bacteria which could work as a cathodic inhibitor is theoretically explained by electro-chemical reactions. And then, this study exemplified the application of the bio-based repair material to concrete with respect to crack repair and patch repair methods. First, alginate-based self-healing materials (in-situ encapsulation) are newly developed in this study to improve the resistance against ingress of water in cracked mortar specimens, which is demonstrated by the reduced absorption of water. This is adequately explained by the fact that the calcite precipitation in gel films formed in crack is highly effective in sealing crack in mortar specimen. In addition, the healing agents could reduce the concentration of dissolved oxygen in concrete, which is found to contribute to reduction of the macrocell corrosion current density in which the corrosion rate is determined by the cathodic reactions associated with diffusion of dissolved oxygen. The use of Bacillus subtilis (natto) is highly advantageous in preventing re-deterioration owing to macrocell corrosion taking place between patch repair region and surrounding concrete containing chloride. c 2022 Elsevier Ltd
Phenomenological process of rebar corrosion in reinforced concrete evaluated by acoustic emission and electrochemical noise
Kawasaki Y.; Fukui S.; Fukuyama T.
Construction and Building Materials, Elsevier Ltd., Vol.352, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.128829)
Abstract
Rebar corrosion was evaluated by monitoring reinforced concrete specimens. An electrical corrosion test accelerated the corrosion, and non-destructive evaluation of the acoustic emission (AE) and electrochemical noise (EN) was applied. Because AE phenomena were detected during rebar corrosion, the rise time and maximum amplitude increased, showing waveform variations. The AE activity was attributed to oxide film peeling of the rebar surface. The pitting index of the EN analysis ranged from ?1 to 0, indicating localized corrosion. The EN method can detect pitting corrosion on rebar surfaces. AE and EN can be combined to phenomenologically evaluate early-stage rebar corrosion in concrete. c 2022 Elsevier Ltd
Mechanisms of high frost scaling resistance of SHCC
Kobayashi K.; Miura S.; Oshima E.; Yun H.-D.
Construction and Building Materials, Elsevier Ltd., Vol.324, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2021.126300)
Abstract
This study aimed at evaluating the scaling resistance of strain-hardening cement-based composite (SHCC) exposed to freezing and thawing cycles. RILEM-CDF test was conducted to clarify which parameters of the composition of SHCC have an impact on the scaling resistance. The investigation was made to determine the influence of the following parameters on the scaling: water cement ratio of the mortar matrix, fiber volume, air volume, and the mixing ratio of non-binding materials, namely limestone powder, quartz sand, and sand. The water cement ratio was set to 0.3, 0.4, and 0.55. The volumetric ratio of fiber and air ranged from 0 to 1.2% and 0.8 to 11.0%, respectively. The CDF test was conducted on trowel-finished surfaces for 60 cycles, and the scaling mass was measured every 6 cycles. The specimen surfaces were observed after the test. Samples were taken out from the center part of the test specimens and pore size distributions were measured. The results indicated a generally high scaling resistance of SHCC, its scaling mass being lower than that of ordinary mortar with the same water cement ratio. Even an SHCC mortar matrix without fiber suffered less scaling than the ordinary mortar having the same water cement ratio. The scaling amount reduced proportionally to the particle size of the non-binding materials, i.e., the finer the non-binding material, the lower the scaling amount, presumably because finer particles make the microstructure denser. The fiber apparently also improved the resistance against the progress of scaling by bridging cracks. c 2021 Elsevier Ltd
The effect of heat treatment on the kinetics of the delayed ettringite formation ? An improved chemo-thermal-hygral model
Kothari C.; Takahashi Y.
Construction and Building Materials, Elsevier Ltd., Vol.331, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.127358)
Abstract
This study investigates the effect of heat treatment on the kinetics of precipitation of the delayed ettringite in concrete structures and a chemical model for concrete expansion due to delayed ettringite formation (DEF). The expansion of concrete structures due to DEF majorly depends on the amount of sulfate, aluminate, and alkali content present in the cement. Apart from these parameters, environmental conditions like saturation, temperature, and duration of heat treatment also play a major role in the kinetics of the formation of delayed ettringite. The thermal energy, which is a function of concrete's high temperature and its duration, can change the concrete's microstructures affecting the kinetics of release of sulfate from the C-S-H gel. Such high temperature curing can also affect the leaching of alkali by modifying the pore structure. A comprehensive chemo-thermo-hygral model for DEF is discussed in this study based on study conducted by previous research. The previous model defines the kinetics of three major phenomenon related to DEF: dissolution of ettringite and monosulfate at high temperature; fixation of aluminate into hydrogarnet during the high-temperature curing; precipitation of delayed ettringite. In the current work, the model is integrated with a multi-component hydration heat model and a new thermal energy factor governing the precipitation kinetics which not only correlates well the final expansion with experimental values, but also closely simulates the kinetics of expansion. A multi-ionic transport model is considered for alkali equilibrium. Finally, the kinetics of DEF along with the chemical expansion is validated with the experimental results from literature. c 2022 Elsevier Ltd
Experimental study on the dynamic properties of rigid polyurethane foam in stress-controlled cyclic uniaxial tests
Koyama A.; Suetsugu D.; Fukubayashi Y.; Mitabe H.
Construction and Building Materials, Elsevier Ltd., Vol.321, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.126377)
Abstract
Frequent major earthquakes in Japan necessitate earthquake-resistant infrastructure. The dynamic deformation characteristics of rigid polyurethane foam, used as a lightweight embankment material, is examined in this study. The effect of the initial static stress on the shear modulus of single-layer samples was small, while the shear modulus of two-layer samples increased with increasing initial static stress. The damping ratio of single-layer samples converged to 4?5%, but decreased with increasing initial static stress up to 30 kPa in two-layer samples before increasing above 40 kPa. Results from cyclic uniaxial and triaxial tests were compared. The dynamic properties depended on restriction conditions and the deformation direction. c 2022 The Authors
Modeling of hydration products and strength development for high-volume fly ash binders
Krishnya S.; Herath C.; Elakneswaran Y.; Gunasekara C.; Law D.W.; Setunge S.
Construction and Building Materials, Elsevier Ltd., Vol.320, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2021.126228)
Abstract
Partial replacement of cement using fly ash, as an environmentally friendly approach, has gained increased attention in construction practice. The realistic prediction of microstructure and mechanical properties of fly ash blended cement paste is therefore noteworthy for many practical applications including selection of construction material and their appraisal of design. In this research work, an integrated framework is proposed and demonstrated for predicting the hydration products and compressive strength of high-volume fly ash binders. The prediction framework is designed to have multiple stages. For computing the hydrates of blended cement paste, a coupled hydration model with thermodynamic modelling is developed. A hierarchical model that captures the development of the paste via multiple levels (from C-S-H globules to blended cement paste) is used subsequently to predict the compressive strength as a function of hydration period. Here, unlike previous works, the formation of C?S?H is realistically modelled by distinguishing it into low- and high-density C?S?H. A series of experiments (including XRD Rietveld analysis, thermo gravimetric analysis, selective dissolution, mercury intrusion porosimetry and compression tests) are performed; hence the predictability of the developed work is assessed by comparing the predicted results with experimental data. A very good agreement is seen between the predicted results (hydration products, pore volume and compressive strength) and experimental results, indicating that the proposed model can be applicable to the high-volume fly ash cement paste to reliably capture the hydrates and compressive strength. It is further noted that with an increase in fly ash replacement ratio, the capillary porosity increases, while the reaction rate and compressive strength decrease. c 2021 Elsevier Ltd
Investigating the hydration characteristics of a new composite cementitious binder containing of slag and calcite
Li C.; Krishnya S.; Ogino M.; Owaki E.; Elakneswaran Y.
Construction and Building Materials, Elsevier Ltd., Vol.361, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.129629)
Abstract
The influence of the filler content, filler fineness and water to powder ratio (W/P) on hydration kinetics and microstructure behaviour of a new clinker-free material made of calcium hydroxide, blast furnace slag (BFS), calcite and expansive agent are explored in this study. The hydration characteristics of the proposed material were investigated by multiple experimental programmes including X-ray diffraction (XRD), TG-differential thermal analysis (DTA), selective dissolution measurement and mercury intrusion porosimetry (MIP). The experimental results revealed that slag reaction degree is enhanced by increasing the filler content and fineness of the filler in high W/P ratio. However, the filler fineness does not show significant improvement in the hydration degree of slag with low W/P ratio in later curing period due to the reduced amount of available water for the hydration reaction. Another interesting finding of this study is that the hemicarboaluminate which is thermodynamically unstable than monocarboaluminate, stably formed even at the later age of hydration reaction in the presence of calcium carbonate. The amended thermodynamic model also well agreed with the tendency of the experimental results in terms of hydration products and porosity of the hardened matrix as a function of curing period. c 2022 Elsevier Ltd
Molecular progress of the corrosion of passivated Iron: The effects of structural strain
Li M.; Wu S.; Wang P.; Zhang J.; Dong B.; Ma M.; Wang Z.; Hou D.; Wang M.
Construction and Building Materials, Elsevier Ltd., Vol.360, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.129537)
Abstract
Structural strain of steel is a general phenomenon in reinforced concrete, which significantly affects the performance of the passivation film but is still unclearly due to its nanoscale characteristics. In this work, the process of the chloride attack on ƒÁ-FeOOH is revealed by the molecular dynamics simulation with different structural strains. It is found that the properties of the ƒÁ-FeOOH structure changed significantly with the increase of strain. In the low strain status, the ƒÁ-FeOOH structure exhibit typical ductility. However, it exhibits obvious brittleness in the high strain state. The analyses of molecular interaction indicate that the chloride is easier to penetrate the layer structure of ƒÁ-FeOOH in high strain status, thus resulting in a huge shift in the ƒÁ-FeOOH properties. The generation of iron hydroxyl induces the penetration of chloride ions and is regarded as the origin of the ƒÁ-FeOOH deterioration. c 2022 Elsevier Ltd
Time-dependent retardation effect of epoxy latexes on cement hydration: Experiments and multi-component hydration model
Li P.; Jiang Z.; An X.; Maekawa K.; Du S.
Construction and Building Materials, Elsevier Ltd., Vol.320, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2021.126282)
Abstract
The kinetics and thermodynamics of the retardation effect of epoxy latexes on cement hydration were investigated using isothermal calorimetry and in-situ x-ray diffraction. The experimental results showed that the retardation effect of epoxy latexes on cement hydration was time-dependent. When the epoxy latexes were added to cement pastes, heat-generation rate was slowed, the hydration induction and acceleration periods were delayed, and the heat-flow maxima were suppressed. The addition of epoxy latexes markedly retarded silicate and aluminate hydrations by retarding both the dissolution of cement clinker minerals and the precipitation of hydration products. Higher epoxy latex content led to even slower cement hydration. Based on these results, a multi-component hydration model for composite cementitious materials, considering the time-dependent retardation effect of epoxy latexes on cement hydration, was established. The numerical results showed that the model showed great potential to predict the kinetics and thermodynamics of cement hydration with different epoxy latex contents, and provided more details about the phase evolution of the clinker minerals during cement hydration. c 2021
Lab-scale reproduction test method for temperature-driven movement of through-thickness cracks in concrete exterior walls for crack repair evaluation
Li Y.; Ohkubo T.; Teramoto A.; Saga K.; Kawashima Y.
Construction and Building Materials, Elsevier Ltd., Vol.331, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.127169)
Abstract
Crack repair is an important process for extending the service life of buildings. Crack movement is one of the factors that affect the durability of crack repair; however, there is no existing method to evaluate the repair under the influence of crack movement. To this end, this paper proposes a lab-scale crack movement reproduction test method to evaluate the effectiveness and durability of the repair. The movement of cracks penetrating the thickness of the concrete wall (through-thickness cracks) was monitored on both the indoor and outdoor sides. The results showed that the through-thickness cracks produced a bending-like movement with movement amplitudes of about 0.03 to 0.08 mm, driven by indoor and outdoor temperature differences; the resulting deterioration pattern in the repair area was a combined outcome of temperature and mechanical loading. The reproduction experimental method was established in reference to numerical simulation. Experimental results verified that the proposed test method satisfies the relationship between movement amplitude and the temperature difference, restraining force, and initial crack width in actual buildings. In addition, the method is stable, with a coefficient of variation of 7.73% in the movement amplitude for ten experimental groups. Furthermore, it was suggested that reducing the temperature gradient in the wall cross-section can reduce the deterioration caused by crack movement. c 2022 Elsevier Ltd
Optimization of mechanical properties and water absorption behavior of building gypsum by ternary matrix mixture
Li Z.; Wang X.; Hou Y.; Wu Z.
Construction and Building Materials, Elsevier Ltd., Vol.350, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.128910)
Abstract
Building gypsum has the disadvantages of low strength and poor water resistance, which limits its wide use. In this paper, the mechanical properties and water absorption behavior of building gypsum by ternary matrix mixture (including cement, fly ash and lime) were optimized. Three maximum levels under the influence of different factors (including cement, fly ash and lime) were initially obtained through single-factor experimental analysis. Next, multifactor experiments were performed using the Box?Behnken design approach. The effects of different multifactor were analyzed using response surface methodology, and relevant prediction models were established and verified. Subsequently, the effects of different factors were verified through optimization mechanism analysis, including thermogravimetric analysis, X-ray diffraction, and scanning electron microscope. The results indicated that the maximum compressive strength and water absorption values were observed at a single-factor impact (including cement, fly ash, and lime) content of 20 %. Prediction models of the compressive strength and water absorption were established, and the proposed models exhibited a high degree of fitness. In addition, the optimum content ratios for the compressive strength and water absorption were cement: fly ash: lime = 10 %: 20 %: 14.86 % and 20 %: 20 %: 14.29 %, respectively. Furthermore, the optimal group exhibited a high intensity, the total weight loss decreased by 35 %. at high temperatures, and a homogeneous structure and distributed crystalline network of gypsum crystals were formed. c 2022 Elsevier Ltd
A study on properties, static and dynamic elastic modulus of recycled concrete under the influence of modified fly ash
Lin H.; Takasu K.; Suyama H.; Koyamada H.; Liu S.
Construction and Building Materials, Elsevier Ltd., Vol.347, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.128585)
Abstract
The effects of modified fly ash (MFA) on the replacement rate of cement, the quality and replacement rate of recycled fine aggregates (RFA), the mechanical properties of concrete, such as compressive strength (fc), static elastic modulus (Ec), dynamic elastic modulus (Ed), and durability, i.e., drying shrinkage (ƒÃ), were investigated in this study. Based on the data and discussion of the results, different linear correlations were found between Ec and Ed, and the concrete's age was found to be an important influencing factor. A new equation about Ec and fc of concrete was proposed, as well as the relationship between Ed and fc, and the correlation coefficients were analyzed by the quality and substitution of recycled fine aggregates, and it was confirmed that they were two important influencing factors. Finally, the correlation between Ed and ƒÃ and the pore volume in the pore diameter interval of concrete was investigated under the influence of the quality and replacement rate of aggregates and the replacement rate of MFA, and it was found that the variation of Ed and ƒÃ on the pore volume correlation coefficient was highly consistent. c 2022 Elsevier Ltd
Research on in-situ corrosion process monitoring and evaluation of reinforced concrete via ultrasonic guided waves
Liu Y.; Ding W.; Zhao P.; Qin L.; Shiotani T.
Construction and Building Materials, Elsevier Ltd., Vol.321, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.126317)
Abstract
A simply strategy for monitoring the corrosion process via the peak-to-peak amplitude of ultrasonic guided waves is performed to capture the initial and cover cracking stage of reinforced concrete. In this study, the accelerated corrosion process of steel in concrete is traced, and three factors (steel type, water-to-cement ratio, and concrete cover thickness) are investigated and analyzed. The results show that the amplitude variation can obey a similar pattern that the minimum value (valley) can identify the initial cracking while the maximum value (peak) can represent the cover cracking condition. Moreover, the steel type shows little effect on the amplitude value, but the higher water-to-cement ratio and the thicker concrete cover thickness can significantly decrease the amplitude value in each monitoring period. This study indicates the potential application of the ultrasonic guided waves amplitude for monitoring the corrosion process. c 2022 Elsevier Ltd
A study on engineering properties and environmental impact of sustainable concrete with fly ash or GGBS
Liu Z.; Takasu K.; Koyamada H.; Suyama H.
Construction and Building Materials, Elsevier Ltd., Vol.316, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2021.125776)
Abstract
In this study, we investigated the compressive strength, drying shrinkage, creep, and CO2 emissions per unit volume of concrete containing fly ash or ground granulated blast-furnace slag (GGBS) as part of cement or fine aggregate. We introduced a parameter KL to capture the effect of fly ash content in the creep prediction model. The results showed that mixing fly ash as part of the fine aggregate in concrete can effectively increase the strength of concrete and reduce shrinkage and creep. Therefore, introducing a parameter to capture the effect of fly ash content in the prediction model can accurately predict the creep strain of concrete. c 2021 Elsevier Ltd
Properties investigation of recycled aggregates and concrete modified by accelerated carbonation through increased temperature
Lu Z.; Tan Q.; Lin J.; Wang D.
Construction and Building Materials, Elsevier Ltd., Vol.341, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.127813)
Abstract
Carbonation can modify waste concrete aggregate and sequester CO2; however, the slow reaction speed in a room environment limits its industrial application. In this study, the carbonation reaction of recycled coarse aggregates were accelerated at 70 ‹C. The physical properties of the recycled coarse aggregate before and after accelerated carbonation treatment and the mechanical properties of recycled concrete were tested and evaluated. Based on the results, an increased carbonation temperature can accelerate the carbonation reaction rate of the recycled concrete aggregate. The calcium hydroxide contained was fully carbonated in the first 12 h. Carbonation modification reduced the water absorption rate to 23.6% and the crushing value to 36.2%. Moreover, the mechanical performance of recycled concrete mixed with carbonation-modified aggregates was evaluated through a uniaxial stress?strain constitutive test. The 28 d compressive strength showed a 14.2% increase at 100% substitution of recycled modified aggregates relative to recycled aggregates. The elastic modulus and brittleness of the recycled concrete were also improved. c 2022 Elsevier Ltd
An analytical investigation of bond deterioration between rebar and ASR/DEF-damaged concrete with and without stirrup confinement using 3D RBSM
Luo J.; Asamoto S.; Nagai K.
Construction and Building Materials, Elsevier Ltd., Vol.351, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.128923)
Abstract
The bond performance between rebar and concrete is essential for the safety of RC structures. There is a need for research on bond deterioration due to the alkali-silica reaction (ASR) and delayed ettringite formation (DEF) damage which affects real structures. In this paper, a parametric study is conducted to quantitatively study the effect of slight-to-severe ASR/DEF damage in the presence of stirrup confinement on the pullout behavior between concrete and reinforcement using three-dimensional rigid body spring model (3D RBSM) simulation. It is found through the simulation that the bond stress in ASR damaged cases increases when ASR expansion before pullout is small and then decreases as the damage level rises, while the bond stress in DEF damaged cases keeps decreasing from the beginning. Besides, higher stirrup confinement effectively mitigates bond deterioration in both ASR and DEF damaged cases when damage is serious. More importantly, stress development and crack propagation during the expansion stage and the pullout stage are visualized. Interface cracking condition varies according to the damage type (ASR or DEF) and the level of stirrup confinement due to different cracking mechanisms. However, the tendency for the number of cracks in the concrete to increase, which reflects the overall damage level in ASR and DEF damaged cases, is similar, resulting in a similar trend for bond stress to decrease. c 2022 Elsevier Ltd
Turning incinerator waste fly ash into interlocking concrete bricks for sustainable development
Nguyen M.H.; Huynh T.-P.
Construction and Building Materials, Elsevier Ltd., Vol.321, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.126385)
Abstract
The reuse of industrial waste plays a vital role in sustainable development in recent years. In this study, the potential of using the densified mixture design algorithm (DMDA) to utilize waste incineration fly ash (IFA) as a cementitious replacement in interlocking concrete brick (ICB) was investigated. The differences in dimensions, visible defects, engineering properties, and long-term performance of ICB samples produced using different IFA replacement ratios (0%, 15%, 30%, 45%, and 60%) were examined. The results indicate that the IFA replacement level affects ICB properties significantly with increasing levels of IFA replacement associated with decreasing compressive strength, abrasion resistance, bending strength, and bulk density whereas increasing water absorption and void volume. The results of a scanning electron micrograph analysis indicate that higher IFA content is associated with a progressively less-homogeneous microstructure. The effectiveness of the DMDA algorithm was clearly verified, as all of the samples were found to comply fully with relevant Vietnamese standards. The relationships among the tested properties were then established and discussed. The findings of this study prove a promising approach for the combination DMDA algorithm and IFA materials in the production of interlocking bricks adapting sustainable development. c 2022 Elsevier Ltd
Effect of temperature on nondestructive measurements for air permeability and water sorptivity of cover concrete
Nguyen M.H.; Nishio S.; Nakarai K.
Construction and Building Materials, Elsevier Ltd., Vol.334, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.127361)
Abstract
The influence of temperature on the transport properties of cover concrete is crucial for adjusting in situ measurements. This study investigated the effects of storage room temperature on air permeability and water sorptivity measurements. Four temperature conditions (5, 20, 30, and 35 ‹C) with constant relative humidity (60%RH) were applied to 11 specimens produced using two types of cement, five water-to-cement ratios, and four curing periods. Three nondestructive methods, namely the Torrent air permeability, surface water absorption, and water intentional spraying tests, were used to monitor the air permeability and water sorptivity changes. With an increase in the temperature, an increase in air permeability and water sorptivity was observed. This increase could primarily be explained by the corresponding changes in the viscosity, surface tension, and surface moisture content under temperature changes. Subsequently, the applicability of three nondestructive methods and strong positive relationships between the obtained results under temperature changes were determined and discussed. c 2022 Elsevier Ltd
Assessment of consistency and strength properties of clays treated with paper sludge ash-based stabilizers using the water absorption and retention rate
Nguyen Phan B.; Sekine R.; Hayano K.; Yamauchi H.
Construction and Building Materials, Elsevier Ltd., Vol.351, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.128936)
Abstract
Paper sludge ash-based stabilizers (PSASs) have recently been developed in Japan as sustainable construction materials for soil stabilization. PSASs are produced by the in-solubilization of heavy metals in paper sludge (PS), which is generated as a by-product of the de-inking and re-pulping of paper. PSASs can improve the stability of high-water-content clays immediately after mixing owing to their good water absorption and retention performance. However, mixture design methods that consider time variations of the water absorption and retention performance of a PSAS are lacking. Therefore, in this study, the effects of a PSAS on the physical and mechanical properties of the treated clay were experimentally investigated, considering the change in the water absorption and retention performance of the PSAS with curing time. The water absorption and retention rate, Wab, of the PSAS, is defined as the ratio of the mass of water absorbed and retained by the PSAS to its dry mass. Physical tests and cone index tests were conducted on different types of clays treated with different types of PSASs. The test results showed that different Wab values were obtained depending on the type of the PSAS and that the Wab value increased with curing time. From the experiments, it was found that the liquid limits, wL, and plastic limits, wP, of the PSAS-treated clays with different curing times could be evaluated from the Wab values of the PSAS and the particle sizes of the PSAS and untreated clays. A clear correlation was also found between the cone index, qc, and liquidity index, IL, of the treated and untreated clays. Based on the results, a new approach for mixture design was proposed. The applicability of the proposed method was investigated, and the results showed that the measured qc value of the PSAS-treated clay was close to the target qc value. The average measured qc was approximately 1.1 times the corresponding target qc. The maximum error between the measured qc and target qc values was approximately 30%. c 2022 Elsevier Ltd
Cold reaction sintering for preparation of ultra-dense geopolymer products
Nishikawa K.; Hashimoto S.; Imai H.; Rossignol S.
Construction and Building Materials, Elsevier Ltd., Vol.328, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.127101)
Abstract
Geopolymers are attractive materials that contribute to carbon neutrality because they can significantly reduce CO2 emissions compared to traditional Portland-based cement manufacturing. Geopolymers generally take several days to weeks to cure and have low mechanical properties. This paper proposes a new hardening method using a warm press, called gcold reaction sinteringg, in order to obtain a hardened body with high strength in a shorter time than conventional geopolymers. In general, to harden geopolymers use an alkaline solution such as NaOH. In this study, sodium metasilicate hydrate (Na2SiO3EnH2O) was used instead of the alkaline solution. As a result of examining the composition, temperature and holding time, the maximum compressive strength value of 425 MPa was obtained when hardened at uniaxial pressure 100 MPa, 130‹ C for only 10 min with fly ash: Na2SiO3: Na2SiO3E9H2O (68: 16: 16 wt%, respectively). In addition, dimensional change measurements during hardening, FTIR and NMR analysis were preformed to investigate and discuss the mechanism of geopolymer hardening. c 2022 Elsevier Ltd
Swelling and strength characteristics of sand treated with paper sludge ash-based stabilizer
Otieboame Djandjieme M.; Hayano K.; Yamauchi H.; Maqsood Z.
Construction and Building Materials, Elsevier Ltd., Vol.341, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.127849)
Abstract
The aim of this study is to investigate the potential of using a paper sludge ash-based stabilizer (PSAS) to improve the properties of sand proposed to be used as a backfill material around underground pipes. The swelling potential and strength of the sand treated with PSAS are investigated by conducting a series of laboratory tests. Similar tests are conducted on sand treated with ordinary Portland cement (OPC). Swelling potential tests show that the PSAS-treated sand with a water content of 0% show significant expansion during soaking, similar to the OPC-treated sand. However, the test results reveal that an appropriate moisture content of the PSAS-treated sand reduces its potential for expansion, depending on the duration of its temporary placement at the construction site. Unconfined compression tests show that the compressive strength of the PSAS-treated sand is significantly lower than that of the OPC-treated sand under the same mixing conditions, even though the chemical composition of PSAS is relatively similar to that of OPC. The increase in compressive strength with the curing time is more gradual in the PSAS-treated sand than in the OPC-treated sand, suggesting that the former is easier to re-excavate. X-ray diffraction profiles showed that the formation of calcite is dominant in the PSAS-treated sand, and that berlinite may be an additional contributor to the increase in strength of PSAS-treated sand in the long term. c 2022 Elsevier Ltd
Dimensional influence of basalt fiber reinforcements on the consolidation behaviour of rice husk ash stabilized soils
Otieno Owino A.; Nahar N.; Hossain Z.; Tamaki N.
Construction and Building Materials, Elsevier Ltd., Vol.339, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.127686)
Abstract
The development of reinforcement techniques in soils with various fibers has been a common practice since the early days. Recently, fibers and materials considered waste are being used to develop sustainable solutions in designing new soil reinforcing and stabilizing materials. In this paper, an investigation has been carried out to evaluate the dimensional influence of basalt fiber on the compressibility and swelling of soils stabilized with rice husk ash (RHA) and cement. Incorporating a nominal dosage of basalt fibers into the soil?cement-RHA composite produces a strong composite with smart material properties. Specimen containing expansive clay soil, basalt fibers (lengths 3 mm, 6 mm, 12 mm), RHA (5%, 10%, and 15%), and cement (3%), in their specified combinations, were prepared and tested. The influence of fiber length and variation of RHA-cement content was quantified using the consolidation curves (compression curves and normalized compression curves), compression index, and swelling index, which provided a detailed behavioral modification upon consolidation. Scanning Electron Microscopy (SEM) and X-ray powder diffraction (XRD) were also used to examine the reconstituted soil structure and chemical components. It is demonstrated that a reconstituted clay soil combination of 12 mm basalt fibers, 5% RHA, and 3% cement, enhanced the ultimate yield pressures and the resistance to excessive swelling. This paper emphasized the projected responses during the loading and unloading phases on the specimen and discussed the consolidation characteristics of the newly reconstituted soil composites. c 2022 Elsevier Ltd
Estimation of restrained expansion strain of reinforced expansive concrete considering mixture and curing conditions
Prayuda H.; Dumaru R.; Tanapornraweekit G.; Tangtermsirikul S.; Saengsoy W.; Matsumoto K.
Construction and Building Materials, Elsevier Ltd., Vol.322, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.126386)
Abstract
Several standards have been used as guidelines for expansive concrete design. However, all of these standards still do not consider several factors that affect the level of expansion such as the incorporation of fly ash, curing temperature, and curing condition. The main objective of this study is to estimate the restrained expansion strain of reinforced expansive concrete by including several factors which affect level of expansion. This research determines the effective free expansion strain of expansive concrete, which is the expansion strain after eliminating the loss of expansion due to the effects of pores filling by expansive products and compression creep during early age restrained expansion. This effective free expansion strain is used as the input of finite element (FE) analysis to estimate the restrained expansion strain. A reduction factor is introduced to account for the loss of expansion. It was found that by the application of the proposed reduction factor, the tested restrained expansion results of specimens with various mixture and curing conditions can be predicted satisfactorily. c 2022 Elsevier Ltd
Field investigation and finite element analysis on expansion and shrinkage strains of expansive concrete structures
Prayuda H.; Tanapornraweekit G.; Tangtermsirikul S.; Matsumoto K.; Jongvisuttisun P.; Snguanyat C.
Construction and Building Materials, Elsevier Ltd., Vol.360, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.129598)
Abstract
This study investigated the strain behavior of various reinforced concrete structures cast with expansive concrete. Laboratory tests, field measurement, and finite element (FE) analysis on the expansion and shrinkage were investigated. Field measurement and numerical simulation were carried out on three different structures, i.e., slab on grade (SG), slab on beam (SB), and water tank wall (WT). Strain gauges are installed in several locations in each structure to study the effects of type and amount of expansive additive and restraining conditions on the level of expansion and shrinkage. To increase the flexibility and versatility of the design process, FE analysis is one of the comprehensive methods for estimating the expansion and shrinkage strain in expansive concrete structures under restraint. FE analysis in this study applies free expansion strain as an input, with the consideration of expansion loss due to pores filling of expansive products and early age compressive creep. The field measurement results indicated that the restraint (internal and external restraint) significantly affects the expansion and shrinkage strains in the structures. Furthermore, it was found that the application of effective free strain as the input in the FE analysis made it possible to predict the level of restrained expansion strain in expansive concrete structures. The expansion and shrinkage strains can be estimated accurately using the FE analysis by considering several factors such as degree of restraint, curing conditions, and mix proportions. c 2022 Elsevier Ltd
Shear-bond behavior of self-compacting geopolymer concrete to conventional concrete
Purwanto; Ekaputri J.J.; Nuroji; Indriyantho B.R.; Han A.; Gan B.S.
Construction and Building Materials, Elsevier Ltd., Vol.321, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2021.126167)
Abstract
The shear-bond behavior of two mechanically different concretes is fundamental when conducting external reinforcement, retrofitting, or repair. The two components are designed to possess full strain compatibility in sustaining the stress transfer between the two parts throughout the loading sequence. This work investigated the shear-bond behavior between conventional and self-compacting geopolymer concrete based on the push-off method. The influence of surface roughness on the bond behavior was studied, and a finite element model was constructed and validated to the experimental data. Surprisingly, the chemical bond characteristics of geopolymer concrete have little effect on the bond strength as compared to conventional concrete having the same compression strengths, but significantly influences the load-slip pattern of the interface. As expected, the bond strength was positively influenced by the interface roughness. All failure modes were unmistakably brittle. The strain deformation pattern generated from the finite element model underlined that large strains and stresses were present at the far ends in the interface, where initial cracking was detected in these regions. The study concluded that self-compacting geopolymer concrete is a perfect solution for older structure's external strengthening or retrofitting. This material has a better sustainable and a more environmentally friendly character. c 2022 Elsevier Ltd
Compressive strength development and durability properties of high-calcium fly ash incorporated concrete in extremely cold weather
Pushpalal D.; Danzandorj S.; Bayarjavkhlan N.; Nishiwaki T.; Yamamoto K.
Construction and Building Materials, Elsevier Ltd., Vol.316, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2021.125801)
Abstract
This research paper takes into account of three mineralogically different high calcium fly ashes (HCFA) consisted of anhydrite, generated in power plants in Ulaanbaatar, Mongolia. The purpose of this research is to understand how the morphology and mineralogy of HCFA influence the fresh and hardened properties of concrete; how pre-curing condition influences the long term strength development in different seasons; and to investigate the durability of HCFA concrete in extreme outdoor exposure conditions and freezing and thawing environment. Compressive strength development of fly ash concretes up to 540 days in extremely cold weather, strength dependence on pre-curing condition, freezing and thawing durability and the influence of ash mineralogy on durability were investigated. As a part of the investigation, the concrete specimens were kept outdoor at sub-zero temperature for more than four months. This paper concludes that strength approximately equal to that of the control can be obtained at early ages by 20 wt% replacement of total cementitious content by fly ash. When a comparison is made with equal mixtures, but equal pre-curing, winter concrete can only be achieved approximately 80% strength of autumn concrete after 3 months and then no considerable improvement happens even at one year. When a comparison is made with equal mixtures, but different pre-curing, the specimens exposed to the outdoor a day after placement show a permanent strength loss of 24%, with compare to the specimens cured in water at 20 ‹C for 28 days before exposing to the outdoor in winter. Durability factors of all fly ash incorporated concretes determined by freezing and thawing test were in the range of 78?91 at 300 cycles, satisfying the threshold in which concrete is likely to perform well. c 2021 Elsevier Ltd
Evaluating compressive strength of concrete made with recycled concrete aggregates using machine learning approach
Quan Tran V.; Quoc Dang V.; Si Ho L.
Construction and Building Materials, Elsevier Ltd., Vol.323, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.126578)
Abstract
To reduce the environmental impact of construction and demolition waste of concrete, recycled concrete aggregate (RCA) has been widely utilized in concrete. The compressive strength of recycled concrete is one of the most important parameters governing the quality of concrete. The compressive strength is determined from the compression test, which requires a huge amount of materials as well as consumes cost and time. Thus, to solve those limitations, this study focused on evaluating the compressive strength of concrete made from RCA using different single and hybrid models of machine learning. Six machine learning models including Gradient Boosting (GB), Extreme Gradient Boosting (XGB), Support Vector Regression (SVR), and three hybrid models of those single models with Particle Swarm Optimization (PSO) namely GB_PSO, XGB_PSO, and SVR_PSO were used to estimate the compressive strength of recycled concrete. The input variables for modeling consisted of cement content, water content, aggregate content, natural aggregate content, recycle concrete aggregate content, sand content, water absorption rates of natural aggregate and RCA. The results of this study show that hybrid models performed better than single models in terms of prediction accuracy. The results indicated that the GB_PSO has the highest prediction accuracy with R = 0.9356, RMSE = 5.5604 MPa, and MAE = 4.2882 MPa. The results of feature importance analysis and partial dependence plots (PDP) analysis revealed that the most important variable effect on compressive strength of concrete made with RAC is cement content, whatever performance strategies of concrete made with RAC. From the results of PDP, the quantity of each material can be computed easily for the designed compressive strength. In the end, this study provides a systematic evaluation of the compressive strength prediction of recycled concrete and has a significant contribution to literature and practice. c 2022 Elsevier Ltd
Experimental investigation on the mechanical and interfacial properties of fiber-reinforced geopolymer layer on the tension zone of normal concrete
Shirai K.; Horii J.; Nakamuta K.; Teo W.
Construction and Building Materials, Elsevier Ltd., Vol.360, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.129568)
Abstract
This study aimed to understand the mechanical and interfacial properties of fiber-reinforced geopolymer (FRG) layer on the tension zone of normal concrete. A trial mix of FRG using local materials obtained in Hokkaido was investigated. Compression and splitting tensile tests on the FRG test pieces were conducted under different mixing procedures, constituents, volume fractions of the polyvinyl alcohol fiber, curing conditions, and ages. Flexural tests using FRG-normal strength concrete (NSC) composite specimens with different FRG layer thicknesses were carried out. By placing the FRG layer on the tension side of the composite specimen, the flexural strength and energy absorption were significantly increased. The flexural strength for the NSC alone was 3.5 MPa, while the FRG-NSC composite specimens showed higher flexural strengths of 6.1?6.6 MPa. Also, XRD, FTIR, and SEM analyses were carried out for the FRG samples. c 2022 The Author(s)
Analytical model of corrosion-induced cracks in concrete considering time-varying deformations of layers, mechanical properties of rust
Tang Bui H.; Maekawa K.; Hai Tan K.
Construction and Building Materials, Elsevier Ltd., Vol.316, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2021.125883)
Abstract
This paper presents an analytical model to simulate the evolution of corrosion-induced cracks in concrete considering the combined effects of time-dependent deformations of layers and mechanical properties of corrosion products applying the principle of equilibrium of force and compatibility of deformations. Stress, strain and deformation in respective layers of corroding steel, rust and uncracked concrete are determined based on elasticity theory, while coupling tensile softening model and elastic modulus reduction is applied to simulate the cracked concrete. Time-varying deformations of four layers and the influence elastic modulus and Poisson's ratio of rust are considered in force equilibrium and compatibility conditions to determine crack length, stress and strain distributions. It is shown that not only the time-to-surface cracking is shortened, the trend of crack development is also altered if the deformations of layers are considered. A higher elastic modulus results in a faster time for cracks to reach the concrete surface, while a larger Poisson's ratio would lead to slower propagation of cracks. By analysing the results obtained from the proposed model and test data, a semi-empirical relationship between applied current density and elastic modulus of rust is recommended. This correlation could be used to predict the elastic modulus of rust which is an important parameter in modelling corrosion-induced cracks in concrete. c 2021
Predicting failure modes and load-capacity of fiber-reinforced polymer rods in adhesively bonded anchorages based on numerical modeling
Vo V.-N.; Nguyen S.-N.; Yoshitake I.
Construction and Building Materials, Elsevier Ltd., Vol.318, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2021.126135)
Abstract
The tensile properties of fiber-reinforced polymer (FRP) rods in adhesively bonded anchorages are expected to be studied in detail. Therefore, the study aims to predict the failure modes and load-bearing capacity (load-capacity) of FRP rods subjected to direct tensile force. The cohesive zone models were employed to evaluate the interfacial bond between materials. Firstly, two representative volume element models of fibers and matrix were proposed to predict engineering constants and strengths of the FRP material in three dimensions. Then, the main simulation, including the FRP rod, filling material, and steel tube, was carried out to analyze FRP rods under the variation of cohesive zone model parameters. The load-capacity, failure modes, shear-lag effect were predicted based on the maximum stress criterion. The results revealed that the FRP material strengths enforce the failure in two modes associated with the transverse and longitudinal directions of FRP rods. In addition, diameter is a significant factor that increases the shear-lag effect and reduces the tensile strength of the FRP rods. The numerical simulation provided a new method to predict the load-capacity of FRP rods. c 2021 Elsevier Ltd
Strategies to accelerate CO2 sequestration of cement-based materials and their application prospects
Wang D.; Xiao J.; Duan Z.
Construction and Building Materials, Elsevier Ltd., Vol.314, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2021.125646)
Abstract
In the past twenty years, significant researches have been conducted on the accelerating fixation technologies of carbon dioxide through the carbonation reaction of cement-based materials. In this study, the published literature on the application of carbonation of cement-based materials for carbon dioxide sequestration has been reviewed, the carbon dioxide sequestration capacity, the carbonation effect on the physical and mechanical behavior of recycled aggregates and concrete, the efficiency improvement methods, and the acceleration methods on the mechanical behavior of cement-based materials are discussed and summarized in detail. The comparative discussion results show that carbonation could effectively improve the mechanical performance of recycled aggregates and concrete. The parameters of liquid water content, sample size, environmental pressure, carbon dioxide concentration, and temperature significantly affect the sequestration efficiency of carbon dioxide of cement-based materials. Besides, the future application proposals of fast carbon dioxide sequestration technologies in the industrial areas and cement-based material recycling have been put forward. This review could facilitate the investigation and application of fast carbon dioxide sequestration technologies through the carbonation of cement-based materials. c 2021 Elsevier Ltd
Effects of phosphorus content on fatigue performance of friction stir welded mild steels
Wang Y.; Tsutsumi S.; Kawakubo T.; Fujii H.
Construction and Building Materials, Elsevier Ltd., Vol.324, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.126682)
Abstract
The weathering steels for bridge construction joined by fusion welding often suffer from the hot cracks due to the phosphorus segregation. The present study assessed the fatigue performance of newly developed weathering steels with high phosphorus content joined by friction stir welding (FSW) below A1 temperature, by which the heat affected zone (HAZ) softening and weld defects were successfully inhibited. The fatigue life of the FSW joints of three mild steels was evaluated and compared to the design curve. The accumulation of plastic deformation in different regions was analysed and various ratcheting behaviors were studied. The influence of weld defects on the fatigue life due to the inadequate downward loading was also classified. The results showed that the fatigue strength of three mild steels was much higher than the FAT112 design curve, and the S-N curves were extremely flat. The base metal region of the FSW specimens where the fracture usually occurred illustrated a larger accumulation of plastic deformation than the weld nugget. The fatigue fracture at the weld nugget was induced by weld defects and the fatigue life was decreased by as long as 14.7 times. c 2022 Elsevier Ltd
Mechanical behavior and models for porosity-free concrete reinforced with high amounts of steel fiber
Yanagida R.; Nakamura T.; Kono K.; Niwa J.
Construction and Building Materials, Elsevier Ltd., Vol.354, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.129098)
Abstract
A new cementitious composite characterized by an extremely high compressive strength (>400 MPa), known as porosity-free concrete (PFC), has been recently developed. Many tests have been conducted to formulate appropriate stress?strain laws for compression and tension. This study clarified that PFC has extremely high compressive strength and post-cracking toughness owing to the reinforcing fibers. In addition, the flexural strength of porosity-free concrete was investigated by combining experimental and numerical analyses. Furthermore, the formulation of the stress?strain law in tension introduced gequivalent characteristic lengthsh to convert the crack width into an equivalent strain. (93 words) c 2022 Elsevier Ltd
Mechanisms of inorganic salts on Ca(OH)2-activated ground granulated blast-furnace slag curing under different temperatures
Zhai Q.; Kurumisawa K.
Construction and Building Materials, Elsevier Ltd., Vol.338, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.127637)
Abstract
This study investigated in detail the coupling effects of curing temperatures (5, 20, and 35 ‹C) and additional activators (Na2SO4, Ca(NO2)2, NaCl, and Na2S2O3) on Ca(OH)2-activated granulated blast-furnace slag (GGBFS). The results show that the early strengths, hydration degree and microstructure of samples depend strongly on the curing temperature and the nature of activators. Activators influence considerably the initial pore solution composition and pH value, while low-pH values and high-Ca2+ activity suppress the dissolution of Ca(OH)2 and the reaction of GGBFS. Elevated temperatures mainly accelerate the hydration of GGBFS in all samples at early age. However, owing to the cross-over effect, there is a negative effect on the properties of the samples with added sodium salts in the middle and late stages of hydration. For samples in which Ca(NO2)2 was added, the early hydration is low owing to the common ion effect, and high temperature plays a facilitating role instead. Furthermore, the apparent activation energy of GGBFS hydration was also determined to explain the observation. Results show that the sample in which the additional activator was added was influenced considerably by the curing temperature, while samples in which Ca(NO2)2 was added were more sensitive to curing temperature changes. c 2022 Elsevier Ltd
Effect of rock shear keys on the shear performance of cold joints in rock-filled concrete structures: Experimental and numerical investigation
Zhou H.; An X.; Ren M.; Li P.; Wang C.
Construction and Building Materials, Elsevier Ltd., Vol.336, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.127315)
Abstract
Rock shear keys have been applied in rock-filled concrete (RFC) cold joints to improve the shear resistance through aggregate interlocking action. However, the failure mechanism of RFC cold joints remains unclear, and the role of rock shear keys has not been quantitatively evaluated. To investigate the effect of rock shear keys, a series of small-scale shear tests of RFC cold joints using experimental and numerical methods were conducted. Various influential factors were considered, including normal pressure, material strength, and the distribution of rock keys. Failure mode, shear capacity, deformation, and their relationship with the influencing factors were analyzed. The results show there are two typical failure modes deriving respectively from self-compacting concrete (SCC) (Mode II) and rocks (Mode I). It's observed the shear capacity is positively correlated with normal pressure, the exposed height, and the number of rock keys. Moreover, the influence of material strength depends on the failure mode. In Mode I, shear capacity increases with the increment of SCC strength. While in Mode II, increasing the rock strength can effectively improve shear capacity. The study of the distribution of rock keys found that when the exposed height is half of the diameter, and the distance is greater than the diameter, rock keys work optimally. Finally, an empirical formula was proposed based on current test results. c 2022 Elsevier Ltd
Degradation behavior of multifunctional carbon fabric-reinforced cementitious matrix composites under anodic polarization
Zhu M.; Zhu J.-H.; Ueda T.; Matsumoto K.
Construction and Building Materials, Elsevier Ltd., Vol.341, 2022, .
(https://doi.org/10.1016/j.conbuildmat.2022.127751)
Abstract
A sustainable repair method that combines impressed current cathodic protection (ICCP) and structural strengthening (SS), called ICCP-SS, has been proposed for reinforced concrete structures suffering from steel corrosion. The key component in an ICCP-SS system is a multifunctional carbon fabric-reinforced cementitious matrix (MCFRCM) composite that simultaneously functions as a tensile reinforcement and an impressed current anode. The MCFRCM composite is investigated in terms of its electrochemical performance and interfacial performance and the degradation caused by anodic polarization in alkaline solution. The results show that a relatively stable electrochemical performance can be maintained for composites polarized at a current density up to 125 mA/m2, while an exponential increase in cell voltage can be seen at higher current densities. The charge density corresponding to the occurrence of the exponential increase in cell voltage is nearly the same for all composites polarized above 125 mA/m2. Besides, the composite shows a decreased maximum pullout force and a failure mode conversion from partial rupture to complete rupture of the carbon fabric with increasing current density. The composite is degraded by the dissolution of carbon filaments due to the anodic oxidation of hydroxyl ions from the pore solution in the matrix, which results in changes in the chemical composition and morphology of the filaments. The degradation of the composite can be further correlated with the electrochemical performance and interfacial performance. c 2022 Elsevier Ltd