Flexural fatigue behavior of low-carbon pavement materials using geopolymer stabilized recycled concrete and recycled glass blends

The growing demand for sustainable construction practices has promoted interest in the adoption of low-carbon materials for pavement infrastructure. Engineered geopolymer binders have emerged as a promising and environmentally friendly alternative to traditional cementitious binders in soil stabilization, offering reduced carbon emissions, while maintaining comparable mechanical properties. This study investigates the feasibility of using two-part geopolymer stabilized recycled concrete aggregate (RCA) and recycled glass (RG) mixtures in sustainable pavement construction. In this regard, RCA and RG were blended in different proportions and stabilized with alkali-activated fly ash (FA), slag (S), and a binary precursor of (FA+S) at a fixed 50:50 ratio for pavements. The effects of RCA/RG proportion, precursor type and dosage, and curing regime on geopolymer stabilized RCA/RG mixtures were investigated by performing unconfined compressive strength (UCS). The optimum geopolymer stabilized RCA/RG mixtures were further characterized for their resilient modulus and flexural performance through conducting repeated loaded triaxial (RLT) and four-point bending tests. The microstructure of geopolymer stabilized RCA/RG samples were studied scanning electron microscopy (SEM) to understand the reinforcing mechanisms for strength gain. The test results suggested that increasing the RG content led to a decrease in the strength of the geopolymer stabilized RCA/RG mixtures. In contrast, increasing the precursor dosages generally resulted higher UCS values of the stabilized RCA/RG mixtures. Overall, FA geopolymer stabilized RCA/RG mixtures had lower UCS compared to S and (FA+S) geopolymer stabilized RCA/RG mixtures. Most of S and (FA+S) geopolymer stabilized RCA/RG mixtures complied the minimum UCS requirement of 3 MPa stipulated by the local road authority, expect for few stabilized RCA/RG mixtures with addition of 5% precursor dosage. Both curing time and temperature play a critical role influencing the strength development of the geopolymer stabilized RCA/RG mixtures. The RLT and four-point bending test results demonstrated that the addition of RG decreased the resilient modulus and fatigue performance of the geopolymer stabilized RCA/RG mixtures. The findings of this study highlight the potential of geopolymer stabilized RCA/RG mixtures as greener construction materials for pavement structures. • Two-part geopolymer stabilization of recycled concrete aggregates (RCA) and recycled glass (RG) for pavement applications. • FA, S and binary (FA+S) based geopolymer was trailed as a low-carbon binders for RCA/RG blends stabilization. • Acceptable strength development and fatigue performance of stabilized RCA/RG blends for pavement construction.