Utilizing recycled plastic aggregates in geopolymeric composites

The global emphasis on low carbon construction materials has brought significant attention to a new class of materials called geopolymers (GPs). GPs have been considered as an alternative to ordinary Portland cement (OPC). The high carbon footprint associated with OPC production warrant looking for a low-carbon substitute. GPs have a significantly lower carbon footprint owing to the fact that it utilizes multiple aluminosilicate industrial wastes and byproducts. The use of recycled plastic aggregates (RPAs) to replace natural aggregates (NAs) in GP mixtures promises additional benefits in reducing the environmental impact in terms of saving natural resources and waste disposal as well as sequestering carbon contained in waste plastics into construction. Knowing the effect of fine and coarse plastic waste aggregates on the performance of GP matrix composites is essential for evaluating the potential of their practical applications and estimating service life. This chapter will analyze and discuss the ongoing research into the GP composites containing RPAs, focusing on material and geometrical properties of RPAs and the underlying mechanisms involved in aggregate–matrix interactions at fresh and hardened states, as well as mechanical strength, durability performance, and microstructural characteristics. Finally, knowledge gaps in the literature are identified and insights and perspectives pertaining to future research developments are offered.