Investigation of eco-friendly fiber-reinforced geopolymer composites incorporating recycled coarse aggregates

Structural-grade geopolymer concrete (GPC) containing metakaolin (MK) was assessed by partial inclusion of recycled coarse aggregate (RCA) to produce environmental-friendly composites. Polypropylene (PP) fiber was also used at different weight ratios. Mechanical and durability properties of GPCs were then evaluated. The impact of fiber and RCA on the microstructure of geopolymer paste and interfacial transition zone in different parts were evaluated. The results indicated no significant change on compressive strength by the inclusion of PP fiber. However, a remarkable improvement in flexural and splitting tensile strength and drying shrinkage was observed through the inclusion of PP fiber. Load-displacement graphs revealed that PP fiber increases the GPC fracture toughness and improves the maximum load capacity. Although the compressive strength of samples decreased by the RCA inclusion, the strengths achieved were still appropriate for structural applications. From microstructural point of view, it was found that fiber and geopolymer paste have a firm bound, which would contribute to constraining the propagation of potential cracks. It was indicated that the combination of 1% PP fiber and 20% RCA in MK-based GPC leads to an eco-friendly concrete mix with appropriate hardening properties that would contribute to the sustainability in the construction industry.