Coal gangue is a type of rock waste product with dark gray color during coal mining and washing. The curing agent stabilizes soils by improving their physico-mechanical properties, allowing the soils to be reused in engineering as the subgrade fill. This study investigates the impact of SAHP curing agent on road performance parameters of coal gangue. The results showed that the road performance parameters of coal gangue increase with the curing agent content. The compressive resilience modulus of 7 days and California bearing ratio of coal gangue with 0.2% curing agent meet the specifications. The scanning electron microscope reveals the presence of agglomerated gels and hexagonal prism crystals between coal gangue particles. The observed crystals are ettringite, and the gels are silicate gel (nSiO2·mH2O) formed by the reaction of Na2O·nSiO2 with CO2 and H2O, as determined by combined X-ray diffraction and energy spectrum analysis. The improved coal gangue by the curing agent can be utilized as subgrade fill, supporting the reuse of coal gangue in highway engineering.
