Potentials of Metakaolin and Sand as Liner Materials for Waste Containment Application

Abstract

The study investigated the suitability of Metakaolin (Mk) admixed with River sand in the stabilization of Black Cotton Soil (BCS). The suitability of material for constructing a liner or cover depends primarily on low hydraulic conductivity; however, most of the construction works involve the use of soil materials. Some of these soil materials, when encountered, may not be suitable or adequate for use due to their poor strength; therefore, there is a need for their stabilization. For this reason, there is a need for effective utilization of different stabilizers to improve the geotechnical properties of liner materials. Hence, the research uses Metakaolin and sand as liner materials for waste containment applications. The BCS was classified as A-7-6 and CH according to the American Association of State Highway and Transportation Officials (AASHTO) and the Unified Soil Classification System (USCS). The soil was stabilized with Metakaolin blended sand at various percentages. A series of tests, such as Compaction test (OMC, MDD), Unconfined Compressive Strength (UCS), Volumetric Shrinkage Strength (VSS) and Hydraulic Conductivity Test (K), were carried out. Optimization and models for estimation of the responses were done by central composite design (CCD). The result showed that the BCS was classified as A-7-6 and CH according to the AASHTO and USCS. The OMC was 9.8%, MDD was 1.69 Mg/m3. The soil has a specific gravity of 2.19, Natural moisture content of 0.71%, LL of 44.9% and PL of 25.8%. The replacement of black cotton soil with Metakaolin and sand reduces the hydraulic conductivity and Volumetric Shrinkage of the soil. The hydraulic conductivity of black cotton soil was 1.66397E^06 while its shrinkage was 8.98%. The best result recorded was achieved at 20% Mk and 20% sand, with hydraulic conductivity and volumetric shrinkage of 1.601E^06 and 4% respectively. Optimization was carried out and models were developed for the estimation of OMC, MDD, VSS, hydraulic conductivity and UCS of admixed black cotton soil. The numerical optimization was done using central composite design, and the ramp plot gave 20% Mk, 5% Sand, 12% OMC, 1.85% MDD, 345 kN/m2 for UCS at 28 days, VSS at 4.4% and 1.7 cm/s for hydraulic conductivity. Finally, 20% Mk and 5% sand were recommended for use as a replacement for BCS.