CONSTRUCTION AND BUILDING MATERIALS(2022 - 2022)
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
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
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
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, = 9.53 mm; U.S. #5, = 15.88 mm, and U.S. #10, = 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
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
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 (), 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 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 on the pore volume correlation coefficient was highly consistent. c 2022 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
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
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