Improvement in Strength Properties of Black Cotton Soil Reinforced with Metakaolin and Calcium Chloride

This study covers the improvement in strength properties of black cotton soil (BCS) using metakaolin (Mk) and calcium chloride (CaCl₂) as stabilizing agents. BCS material when encountered may not be suitable or adequate for use as subbase material due to poor strength, therefore the need for its stabilization.To maximize the enhancement of the geotechnical properties of BCS, the proportions of Mk and CaCl₂ were optimized using a central composite design (CCD). The findings of the preliminary investigation indicated that BCS had moisture content of 25.3%. The soil's high flexibility was validated by the BCS's liquid limit, plastic limit, and plasticity index, which were 66.8, 35.2, and 31.6%, respectively. According to the American Association of States Highway and Transportation Officials, the soil was categorized as clay of high plasticity (CH) and A-7-6 (13) by the Atterberg limits and sieve analysis test. The UCS and CBR of admixed black cotton soil with metakaolin and calcium chloride were optimized. The central composite design was used for numerical optimization, and the ramp plot revealed that the optimal replacement was 18% Metakaolin and 2% Calcium Chloride. Regression models for prediction of CBR and UCS were developed. Finally, this study revealed that more studies should be conducted to assess the impact of more locally accessible resources that may be utilized to enhance black cotton soil.