Investigation on the Stabilization of High Compressibility Soil with Wood Ash and Cement

Abstract

Weak and soft soils pose serious problems in many areas, especially in Bangladesh, and frequently lead to the structural failure of roads, pavements, embankments, and other crucial infrastructures underscoring the vital role of geotechnical engineering in fostering sustainable and resilient construction. This study explores the effectiveness of wood ash (WA) and cement (C) as stabilizing additives for enhancing the engineering characteristics of highly compressible silty clay soils. XRF analysis confirmed the presence of reactive oxides conducive to pozzolanic reactions. Laboratory investigations were performed on soil samples incorporating varying proportions of WA (0%, 4%, 8%, 12%, and 16%) and equivalent WA contents supplemented with 2% C. The findings indicated that specific gravity decreased progressively with increasing WA content but exhibited a slight increase when C was incorporated. Both the liquid limit and plastic limit rose with WA and WA–C additions, whereas the plasticity index and linear shrinkage declined consistently. The unconfined compressive strength (UCS) demonstrated an upward trend with increasing WA, achieving further enhancement upon C inclusion. Consolidation test results showed a reduction in the volume compressibility (m_V) and compression index (C_C) with higher WA content, which further decreased upon the addition of 2% C. These findings suggest that combining WA and C significantly enhances soil performance, providing an economic and environmentally sustainable method for stabilizing weak subgrade soils.