Laboratory Assessment of Metakaolin Effect on the Volumetric Shrinkage of Black Cotton Soil for Flexible Pavement Construction

A dark grey Black Cotton soil treated with up to 24% Metakaolin content was compacted using British standard light (BSL),West African standard (WAS) or “intermediate”and British standard heavy (BSH) compactive efforts at moulding water contents -2, 0, 2, 4 and 6% of optimum moisture content. Specimens where extruded from compaction moulds and allowed to air dry on the table in the Laboratory in order to assess the effect of Volumetric Shrinkage on the material for use in Flexible Pavement construction. Results recorded showed that Volumetric Shrinkage strain (VSS) values were large within the first 5 days of drying; VSS values increased with higher moulding water content,water content relative to optimum. Generally, the Metakaolin improves the Shrinkage properties of the expansive soil irrespective of the compactive effort. Volumetric Shrinkage potential reduced by about 76%, 61% and 42% at 24% Metakaolin for the WAS, BSL and BSH compactive efforts respectively, as compared to the Virgin soil. It can be concluded that the Metakaolin had shown promising influence on the Shrinkage properties of expansive soil, thereby giving an advantage in improvement of problematic expansive soils. Keywords: Expansive soil, Volumetric Shrinkage Strain, Metakaolin, Compactive effort,Moulding Water content, Flexible Pavement