Compressive and shear behaviour of high-water quick-setting material modified collapsible loess subgrade

This paper proposed a conceptual material to construct the road subgrade, for which the high-water quick-setting material is adopted to modify the collapsible loess. To verify the feasibility and easy-to-construct of this innovative construction material, a series of mechanical tests were carried out to investigate the compressive and shear behaviour of high-water quick-setting material modified Ili loess. The results demonstrate that the high-water quick-setting material significantly enhances the early-stage strength of loess. The mechanical analysis indicates that both the unconfined compressive strength and elastic modulus reach their maximum values at a soil-to-binder ratio (S/B) of 3:1, but gradually decrease as the water-to-binder ratio (W/B) increases. Cohesion shows a continuous decline with higher W/B ratio, while the internal friction angle is most significantly improved at the optimal S/B ratio of 3:1. the scanning electron microscope (SEM) results confirmed that ettringite (AFt) and calcium silicate hydrate (C-S-H) gel are key contributors to strength enhancement, with NMR analysis indicating optimized porosity at favorable mix proportions. Water immersion tests identified an optimum formulation that maintained high structural stability under wet conditions, as evidenced by its exceptional softening characteristics. An integrated engineering adaptation model was established by correlating mix parameters with mechanical properties, balancing strength and admixture content. The high-water material demonstrate effective improvement of collapsible loess, significantly enhancing its engineering performance and validating its suitability for loess subgrade construction.