Gypsum and rice husk ash for sustainable stabilization of forest road subgrade

Forest roads are crucial for economic development and resource accessibility, especially in regions with extensive wood demand driven by construction growth. These roads require consistent maintenance to prevent structural issues, even though they experience lower traffic. Traditionally, gypsum has been used for soil stabilization due to its cation exchange capability with clay minerals and flocculation properties. However, its water solubility in wet conditions necessitates innovative solutions. This study explores a novel approach by combining gypsum with rice husk ash (RHA), an abundant agricultural waste, to address the challenges posed by expansive and low-bearing clay soils in forest road construction. In this study, an expansive soil with high plasticity and swelling potential is treated with varying combinations of RHA (5–20%) and gypsum (2–6%), followed by curing for 7, 15 and 30 days. Mechanical property tests revealed reduced plasticity and swelling pressure, alongside increased unconfined compressive strength. Microscopic analysis illustrated the formation of calcium silicate hydrate (CSH) and calcium aluminosilicate hydrate (CAH) gels, which possibly contributes to improved stability. This research underscores the potential of sustainable soil stabilization using gypsum and RHA synergy to fortify forest roads against expansive clay soil challenges, promoting eco-friendly and resilient infrastructure solutions.