Journal of Materials in Civil Engineering(2022 - 2023)
Subgrade Strength Performance Behavior of Alkali-Activated Binder and Cement Stabilized Expansive Soil: A Semifield Study
Syed M.; Guharay A.; Raju S.
Journal of Materials in Civil Engineering, American Society of Civil Engineers, Vol.35, 2023, .
(https://doi.org/10.1061/JMCEE7.MTENG-15580)
Abstract
Expansive subgrade soil possesses a dual nature of swelling and shrinkage, resulting in a premature failure on pavement surfaces. In the present investigation, an effort has been made to compare the field performance of expansive subgrade soil stabilized with cement and an alkali-activated binder (AAB). A 12-m-long semifield test section with cement, AAB treated, and untreated expansive soil as a subgrade was constructed to evaluate the strength properties. The AAB was produced by combining dry pozzolanic precursors (steel slag and fly ash) with an activator solution (sodium silicate and sodium hydroxide) in a 0.4 w/s ratio. The in situ subgrade strength behavior was evaluated by embedding a series of stress meters and strain gauges in the subgrade layer and applying a load through a dual wheel truck load (12-t rear axle load) on the test section. The influences of AAB, curing time, and steel slag/fly ash proportion in alkaline soil mixture on microstructural and geomechanical properties of soil were analyzed on samples collected from the field section. It is observed that the AAB treated subgrade layers achieved higher geomechanical strength than cement treated and untreated layers. The combined inclusion of slag-fly ash in the AAB mixture increases the subgrade strength by 23%-26% compared to cement treated soil. The recommendations for practical implementation of AAB stabilization for expansive soils as a subgrade are provided based on the semifield test section studies. c 2023 American Society of Civil Engineers.
Compressive Behavior and Durability Performance of High-Volume Fly-Ash Concrete with Plastic Waste and Graphene Nanoplatelets by Using Response-Surface Methodology
Adamu M.; Trabanpruek P.; Limwibul V.; Jongvivatsakul P.; Iwanami M.; Likitlersuang S.
Journal of Materials in Civil Engineering, American Society of Civil Engineers, Vol.34, 2022, .
(https://doi.org/10.1061/(ASCE)MT.1943-5533.0004377)
Abstract
Plastic waste (PW) generation continuously increases every year due to the growing population and demand for plastic materials. This situation poses a challenge to many countries, including developed ones, on how to dispose of PW. Accordingly, PW was utilized in this study to replace coarse aggregates partially in high-volume fly-ash (HVFA) concrete. However, PW decreased the strength and durability of concrete. To address this issue, graphene nanoplatelets (GNPs) were added to mitigate the negative consequences of PW and HVFA on concrete's properties. The objective of this study is to investigate the influences of PW and GNP contents on the durability and deformation of HVFA concrete. Response-surface methodology (RSM) was used to design and optimize a series of cement mixes to achieve the most desirable properties. Independent variables included PW content as partial replacement for coarse aggregates (0%, 15%, 30%, 45%, and 60% by volume), fly ash as partial substitute for cement (0%, 20%, 40%, 60%, and 80% by volume), and GNPs as additives (0%, 0.075%, 0.15%, 0.225%, and 0.3%). The considered responses were concrete unit weight, modulus of elasticity (MoE), and Cantabro abrasion loss at 300 revolutions. Results showed that PW and HVFA decreased concrete unit weight and MoE but increased Cantabro abrasion loss. By contrast, GNPs increased concrete unit weight and MoE but decreased Cantabro abrasion loss. PW and HVFA also increased the compressive toughness and porosity of concrete, while GNPs increased its stiffness but decreased its compressive toughness and porosity. The mathematical models developed to predict the unit weight, MoE, and abrasion resistance of concrete were significant, with errors of less than 6%. An optimized mix was achieved by partially replacing 12.44% of coarse aggregates with PW and 24.57% of cement with fly ash and adding 0.279% GNPs with a desirability of 100%. c 2022 American Society of Civil Engineers.
Modeling the Drying Shrinkage of Cement Paste Prepared with Wastewater
Kong Y.K.; Chu S.H.
Journal of Materials in Civil Engineering, American Society of Civil Engineers, Vol.34, 2022, .
(https://doi.org/10.1061/(ASCE)MT.1943-5533.0004249)
Abstract
In the majority of the world, tap water is not available for construction and water containing various salts is the only choice. However, the effect of such water has not been scrutinized systematically. In this work, the mechanism of the drying shrinkage of ordinary Portland cement paste prepared with various salts was investigated systematically. The paste was prepared with wastewater containing three types of salts, i.e., sodium hydroxide (NaOH), sodium sulfate (Na2SO4), and calcium sulfate (CaSO4), and cured at two different relative humidity (RH) conditions. Various fresh and hardened properties of the mixtures were examined. Tests results showed that the workability decreased with the addition of various salts, among which NaOH produced rapid setting, whereas Na2SO4 was more effective than NaOH and CaSO4 at improving the strength of cement paste. Moreover, the addition of various salts produced a larger magnitude of drying shrinkage, and the drying shrinkage of cement paste was less at higher RH. A robust mathematical model for drying shrinkage of cement paste was established considering physical and chemical meanings. The mechanism is discussed using a conceptual model. c 2022 American Society of Civil Engineers.
Prediction of the Maximum Compressive Strength Geopolymers Using the Method of Weighted Chemical Compositions of Binders
Koumoto T.; Kang H.-B.; Takahashi A.; Komoto S.
Journal of Materials in Civil Engineering, American Society of Civil Engineers, Vol.34, 2022, .
(https://doi.org/10.1061/(ASCE)MT.1943-5533.0004464)
Abstract
Geopolymers are composite hard materials made by mixing solid binders such as fly ash and slag, and alkaline liquid activators such as NaOH and sodium silicate. Geopolymers have recently been developed to be used as a replacement for portland cement concrete. Industrial by-products, such as fly ash, steel making slags and garbage melting furnace slags, can be used to create geopolymers in a process that emits less carbon dioxide than does cement making. This reduction in CO2 emission is important because CO2 is one of the substances known to contribute to global warming. In the future, further uses of these fly ashes and slags must be explored. The development of high compressive strength geopolymers using fly ash and slags will strongly contribute to the fields of construction, geotechnical engineering, and architecture. The compressive strength of geopolymers, qu, is generally considered to be a function of the weight ratio of activator to binder, w, and the weight ratio of NaOH to sodium silicate, ā. The maximum compressive strength, qumax, is determined as the maximum value among the peak values of qu, which were obtained for various values of w and v. The values of w and ā that yield the maximum compressive strength, qumax, are defined as the optimum values wopt and āopt, respectively. When designing geopolymers, it is essential to establish a method to predict qumax using the chemical compositions of the binders only. This research first determines the chemical and physical properties of geopolymer materials by using scanning electron microscopy (SEM) and X-ray diffraction (XRD) observations, and then determines the mechanical properties of qumax, and finally devises a method to predict qumax by combining SiO2, Al2O3, and CaO in binders. c 2022 American Society of Civil Engineers.