Abstract: To investigate the influence of lignin on the water-stability performance of red clay, this study conducted indoor wetting-disintegration tests and performed a systematic analysis on lignin-fiber-reinforced red clay, from which corresponding disintegration curves were obtained. The results show that, without curing, the incorporation of lignin weakens the water-retention capacity of red clay and reduces its water stability. As the lignin content increases, the disintegration time of red clay exhibits a general increasing trend. For cured specimens, the disintegration amount decreases progressively with higher lignin-fiber content, and a relatively stable disintegration process is observed within the first two hours, although complete disintegration does not occur. The study further reveals that curing age has a significant effect on the water stability of red clay: with longer curing periods, the soil’s water stability improves and its resistance to disintegration increases. In uncured specimens, the average disintegration rate first increases and then decreases with rising lignin-fiber content. In contrast, after curing, the average disintegration rate decreases steadily as lignin content increases. An inverse relationship is observed between the average disintegration rate and curing age.

Key words: Red Clay, Wetting Disintegration Test, Lignin, Curing age