High water content material modified collapsible loess subgrade: concept and behaviour

This paper proposed a conceptual material to construct the road subgrade, for which the high water content and quick setting material (e.g., high water material) is adopted to modify the collapsible loess. To verify the feasibility and easy-to-construct of this innovative construction material, a series of static tests were carried out to investigate the compressive and shear behaviour of high water content material modified Ili loess. The results demonstrate that the high-water rapid-setting material significantly enhances the early-stage strength of loess. Mechanical analysis revealed that the unconfined compressive strength (UCS) and elastic modulus peaked at a soil-to-binder ratio (S/C) of 3:1, decreasing with increasing water-to-binder ratio (W/C). Cohesion (c) declined as W/C increased, while the internal friction angle (φ) showed the most pronounced improvement at S/C = 3.0. 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 S/C ratios reduce porosity. Water immersion tests identified the optimal mix ratio as W/C = 1:1 + S/C = 3:1, achieving a softening coefficient K = 0.89 and superior water resistance. An integrated engineering adaptation model was established by correlating mix parameters with mechanical properties, balancing strength and cost-effectiveness. that is, the high-water material demonstrate effective improvement of collapsible loess, significantly enhancing its engineering performance and validating its suitability for loess subgrade construction.