Study on road, mechanical, interface performance, and sustainability of semi-flexible pavement using geopolymer as grouting material

Geopolymers utilize industrial waste as raw materials, offering benefits such as environmental sustainability, rapid strength development, accelerated hardening and high-temperature resistance. They serve as an effective alternative to Ordinary Portland Cement (OPC) for semi-flexible pavement (SFP) grouting applications. This study first involved the mix design of open-graded asphalt (OGA) mixtures and geopolymers, including the original geopolymer (OG) and modified geopolymer (MG). Furthermore, the SFP mixtures infused with two types of geopolymers were cured, and the road and mechanical performance were evaluated at the specified time intervals (7 days, 14 days, and 28 days). Finally, the failure mode of SFP mixtures and the adhesion characteristics of OG and MG with asphalt were examined comprehensively by macroscopic test (low-temperature bending beam test), mesoscopic test (pull-out test), and microscopic tests (contact angle and infrared spectroscopy tests). The results indicate that, in comparison to OG, the SFP mixtures utilizing MG as the grouting agent exhibit superior performance at each stage of the curing cycle. The geopolymer-asphalt interface remains the vulnerable junction in SFP mixtures. MG shows improved bonding strength with asphalt throughout a range of curing ages and greater adsorption ability with asphalt. During the entire life cycle (LC), SFP-MG can reduce the number of maintenance times, resulting in high sustainability.