Design and Properties of Sustainable Geopolymeric Recycled Aggregate Concrete

University of Technology Sydney. Faculty of Engineering and Information Technology.Geopolymeric recycled aggregate concrete (GRAC) is a type of geopolymeric concrete that recycled aggregate (RA) was utilized to replace the virgin aggregate. Thus, GRAC can provide the environmental benefits of both geopolymeric concrete and recycled aggregate concrete (RAC). Specifically, geopolymeric concrete offers a valuable method for recycling industrial byproducts and reducing greenhouse gas emissions associated with the production of ordinary Portland cement. As for the RAC, the merits consist of, but not limited to, the avoidance of natural resource extraction, reduced landfills of construction and demolition waste (C&DW), and diminished transportation of wastes. Accordingly, GRAC suggests a route with a high degree of environmental friendliness for concrete materials. In this study, fly ash and ground granulated blast furnace slag combination based geopolymeric concrete incorporating C&DW based RA was developed and evaluated. Firstly, the engineering properties of GRAC were studied. Subsequently, quasi-static and dynamic compressive tests were conducted on GRAC, respectively, by using a high-force servo-hydraulic test system and a Ø80-mm split Hopkinson pressure bar apparatus. Special attention was devoted to the failure patterns, stress-strain curves, and energy absorption capacity. Moreover, the failure process and mechanism of GRAC under compression was investigated with the help of a digital image correlation system. Existing studies have validated that external confinement by confining materials is an effective strategy to enhance the mechanical and long-term performance of RAC or even to qualify RAC with structural purposes. Therefore, carbon fiber-reinforced polymer (CFRP) material was utilized in this study to provide external confinement for GRAC. Experimental studies on the mechanical behaviors of CFRP-confined GRAC under monotonic and cyclic compression were carried out. The failure model, stress-strain relationship, and axial-lateral strain relationship were investigated. Further, the results were compared with the predictions by existing models to evaluate these models' applicability to CFRP-confined GRAC. Overall, this study could support the producers of C&DW to gain considerable interest by applying the C&DW-based RA into geopolymeric concrete and can benefit the stakeholders of geopolymeric material industries who seek more sustainability in their products