Alkali-activated system of carbide lime and rice husk for granular soil stabilisation

This study investigated the utilisation of an alkali-activated system to stabilise a granular soil. Rice husk ash (RHA) was used as the precursor and carbide lime (CL) as the activator. An experimental programme was carried out to analyse the strength and stiffness of sand–RHA–CL mixtures. Different binder contents (10 and 20%), densities (15.5, 16.5, 17.5 kN/m³), curing periods (7 and 28 days) and calcium/silicon dioxide (Ca/SiO₂) ratios (1, 1.5, 2) were evaluated. Microstructural analyses were conducted on the mixed materials. The increase in binder content, dry density and curing period led to the improvement of strength and stiffness, while the increase in calcium/silicon dioxide ratio hindered the mechanical behaviour. The statistical analysis revealed that all factors studied influenced the mechanical behaviour of soil–binder mixtures. The condition to obtain the highest strength and stiffness was evidenced in the combination of higher dry unit weight, binder content, curing period and lower molar ratio. The alkali-activated system was shown to be a promising binder agent for soil stabilisation for both strength and stiffness. Finally, two calcium aluminosilicate hydrate structures were identified in the soil–binder mixtures, soulunite and jaffeite, indicating ideal structures for the composition of cement hydrates.