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In spite of the considerable research on the mechanical and durability properties of geopolymer concrete, its widespread applicability is hindered due to the difficulties involved in achieving ambient curing conditions and awareness of the effective utilization of industrial by-products. This study investigates the physical and microstructure characterization of sustainable geopolymer concrete (GPC) developed with copper slag as a replacement for fine aggregate. In total, forty-four geopolymer concrete mixtures were prepared to examine their fresh and hardened properties. Four different NaOH molarities (10, 12, 14 and 16) and the replacement levels of copper slag, ranging from 0 to 100% with an increase of 10%, were considered as variables in this research. The study parameters examined includes the fresh (slump) and hardened concrete properties. Additionally, the microstructural characterization for different mixes were studied using the Fourier Transform Infrared Spectroscopy (FTIR), Electron Dispersive Spectrum (EDS) analyses and Scanning Electron Microscope (SEM). Results indicated that replacing fine aggregate with copper slag up to 100% showed no strength reduction. Increasing the molarity of the NaOH solution to 16M led to an increased strength of about 35% compared to the concrete with 10 M in all the mixes. The microstructural analysis performed using SEM/EDS and FTIR showed that a cohesive and fully compact geopolymer matrix was achieved together with the use of low-calcium fly ash and copper slag under ambient curing conditions.

The shear behavior of innovative engineered cementitious composites (ECC) members with a hybrid mix of polyvinyl alcohol (PVA) and polypropylene (PP) fibers is examined. The overall objective of the investigation is to understand the shear behavior of ECC beams with different mono and hybrid fiber combinations without compromising the strength and ductility. Four different configurations of beams were prepared and tested, including 2.0% of PP fibers, 2.0% of PVA fibers, 2.0% of steel fibers and hybrid PVA and PP fibers (i.e., 1% PP and 1% PVA). In addition to the tests, a detailed nonlinear finite element (FE) analysis was accomplished using the commercial ABAQUS software. The validated FE model was used to perform an extensive parametric investigation to optimize the design parameters for the hybrid-fiber-reinforced ECC beams under shear. The results revealed that the use of hybrid PVA and PP fibers improved the performance by enhancing the overall strength and ductility compared to the steel and PP-fiber-based ECC beams. Incorporating hybrid fibers into ECC beams increased the critical shear crack angle, indicating the transition of a failure from a brittle diagonal tension to a ductile bending.

The present work investigates the mechanical and chemical characteristics and durability of high-strength geopolymer concrete (HSGPC) developed using high-volume copper slag and micro silica. The objective of the study was to explore the feasibility of deploying high-volume copper slag as a replacement for river sand in the fabrication of high-strength geopolymer concrete. In total, 11 different trials were cast by varying copper slag up to 100% as a potential alternative for the river sand. The mixture of alkaline activators for the preparation of the geopolymer concrete (GPC), such as sodium silicate (Na2SiO3) and sodium hydroxide (12 M NaOH), was used in the ratio 2.5:1. The optimum mix was selected from different copper slag dosages based on the characteristics of the HSGPC, such as mechanical strength and workability. For the selected optimized mix, micro silica was added up to 5% by volume of the binder (i.e., 1%, 2%, 3%, 4% and 5%) to improve the particle packing density of the developed HSGPC mix which in turn further enhances the strength and durability properties. Two different curing methods, including (a) ambient curing and (b) steam curing at 80 °C, were deployed for achieving the polymerization reaction (i.e., the formation of Na-Al-Si-H gel). Experimental outcomes reveal a maximum compressive strength of 79.0 MPa when 2% micro silica was added to the optimized GPC mix. In addition to the mechanical tests, the quality of the developed HSGPC was assessed using the ultrasonic pulse velocity (UPV) tests, water-absorption tests, sorptivity tests and microstructural analyses.

Maintenance of reinforced concrete (RC) structures has become a global issue due to the problems associated with the corrosion of steel reinforcement. Corrosion of RC structures results in severe serviceability and strength issues, which in turn necessitates major repair works. Though it is difficult to eliminate the risk of corrosion in RC structures, appropriate retrofitting procedures can be implemented to restore the lost strength. This paper presents a detailed analysis of the mechanism of corrosion in RC members and the procedure for retrofitting corrosion-damaged RC members subjected to different loading conditions. Moreover, the efficiency of existing strengthening techniques, such as steel jacketing, fiber-reinforced polymer (FRP) composites, engineered cementitious composites (ECCs), ferrocement jacketing, fabric-reinforced cementitious composites (FRCMs) and ultra-high-toughness cementitious composites (UHTCCs), are evaluated and compared in relation to restoring/enhancing the performance of corrosion-damaged RC members under different loading scenarios. Moreover, the paper provides a detailed comparison of the effects of different parameters governing the corrosion mechanism and suggests suitable design recommendations for improving the overall performance of corrosion-damaged RC members.