Study on the Improvement of Red Clay Cracks Using SA-LRS Crosslinking Material

Red clay is prone to softening upon water infiltration and cracking after dehydration; its internal structure easily deteriorates under dry-wet cycles, which limits its application in slope ecological restoration and resource utilization of engineering spoil. To improve its crack resistance, water stability, and environmental friendliness, sodium alginate (SA) and lotus rhizome starch (LRS) were selected to modify red clay using single-admixture and composite crosslinking schemes. Through six dry-wet cycles, combined with crack observation, image binarization, and surface crack ratio analysis, the evolution law and mechanism of cracks were revealed. The results show that after six dry-wet cycles, the crack ratio of raw red clay increased from 0.89% to 2.75%, and the cracks gradually developed into a penetrating network structure, resulting in irreversible structural damage. Single addition of LRS can inhibit cracking through flexible cementation and pore filling, achieving an optimal crack ratio of 1.82%. Low dosage of SA presents a favorable modification effect, while excessive SA dosage aggravates crack development. The SA-LRS crosslinked group exhibits the best crack resistance; the 1:1 proportion group records a crack ratio of only 0.90%, which is 1.85% lower than that of raw soil. The composite network formed by crosslinking can strengthen particle bonding, optimize pore structure, slow down water migration, and relieve shrinkage stress, thereby effectively restraining the initiation, propagation, and connection of cracks.