Investigation of the Impact of Lime and Nano-Silica on the California Bearing Ratio of Treated Lateritic Soil

Abstract

This study assessed the effect of lime and nano-silica additives on the engineering behavior of lateritic soil from Iyamho, Edo State, Nigeria, with emphasis on index properties, compaction, and California Bearing Ratio (CBR) performance. Laboratory tests were conducted in line with ASTM standards, and a Taguchi L25 orthogonal array experimental design was adopted to optimize additive proportions while reducing experimental runs. The results revealed that stabilization reduced the plasticity index from 7.72% to 3.42%, signifying improved workability and reduced shrink–swell potential. Compaction tests showed an increase in optimum moisture content (from 13.25% to 15.25%) and a decrease in maximum dry density (from 1.90 g/cm³ to 1.75–1.78 g/cm³), reflecting higher water demand and partial replacement of soil particles.

The CBR values declined from 15.15% in untreated soil to 5.15–6.15% in treated samples, although partial recovery (14.06%) was observed at 10% additive content. Regression modeling indicated a negative linear relationship (R² = 51.36%) between additive content and short-term CBR, while Taguchi optimization identified the best performance at 80–85% soil, 2.5–5% lime, and 0–2.5% nano-silica, yielding CBR values above 17%. The study concludes that moderate lime contents (2.5–5%) combined with minimal nano-silica provide the most effective balance between soil strength and workability, making this approach a cost-efficient and sustainable solution for pavement subgrade improvement in tropical environments.