Feasibility of the use of recycled geopolymer concrete coarse aggregates (RGCCA) in pavement quality geopolymer concrete (PQGC)

This paper discusses the findings of an experimental investigation on the effect of recycled geopolymer concrete aggregates as coarse aggregates (RGCCA) in pavement quality geopolymer concrete (PQGC). This study evaluated the replacement of coarse natural aggregates (CNA) with coarse recycled geopolymer concrete aggregates (RGCCA) at 0%, 25%, 50%, 75% and 100% in ambient-cured PQGC mixes. A wide variety of fundamental and mechanical properties of GPC mixes, such as slump, density, ultrasonic pulse velocity (USPV), compressive strength, split and flexural tensile strength, modulus of elasticity and durability properties, such as water absorption, porosity, sorptivity and drying shrinkage, were explored. The findings show that RGCCAs in PQGC have great potential for compressive, split, and flexural tensile strength and modulus of elasticity with less than 10% and a decrease in 50% replacement of CNAs with RGCCAs. The adhered geopolymer mortar on the natural coarse aggregate in RGCCA resulted in reduced mechanical performance, increased water absorption, and higher drying shrinkage. The mixes with up to 50% RGCCA in PQGC met the required strength parameters as per MoRTH 2013 PQC standards. However, an additional inclusion of RGCCAs content in PQGC has been shown to have more substantial negative impacts on the mechanical performance. Based on laboratory investigation, it has been found that using up to 50% coarse RGCA in PQGC mixes is suitable for the construction of major highways without substantially compromising strength. On the other hand, it is recommended to use 100% RGCCA for low-volume roads and in lower layers of pavement.