Compaction Behaviour of Lateritic Soils Stabilized with Blends of Groundnut Shell Ash and Metakaolin

Abstract

The study investigates the potential of groundnut shell ash (GSA) - Metakaolin (MK) blend for stabilization of lateritic soil, with a view to improving the properties of lateritic soils for road construction. In flexible pavements lateritic soil are used as materials for sub-grade and sub-base construction. In some cases lateritic soils pose serious challenges when encountered as road construction materials due to the presence of clay. The soil was classified as A-2-6(0) and CL according to the American Association of State Highway and Transport Officials (AASHTO) and Unified Soil Classification System (USCS) Classifications. Chemical analysis revealed that the soil is lateritic soil due to the Silica - sesquioxide ratio which falls within the ranged 1.33 to 2.00 as defined by Bell (1993). The soil was stabilized with increment of 2-10% GSA and 5-25%MK by weight of the dry soil. The laboratory tests were carried out using three energy levels such as British Standard light (BSL), British Standard heavy (BSH) and West African Standard (WAS). California bearing ratio (CBR), Unconfined Compressive strength (UCS), and Compaction test were also carried out. The result obtained showed a decrease in plasticity index (PI), Liquid limit (LL), plastic limit (PL), and water absorption. There was an increase in Maximum dry density (MDD) with increase in GSA and MK contents in the mix proportions used. There was also improvement in the CBR which resulted to an optimum of 36%, 154% and 81% using BSL, BSH and WAS compactive effort respectively; which met the acceptable requirement for sub-grade, sub-base and base course of highly trafficked roads in Nigeria. The UCS values at 7 days cured of 402, 731 and 530kN/m² fell short of 1710kN/m² and 1034.25kN/m² evaluated in the criteria recommended by TRRL road Note: 31 and Nigerian General Specification for Road and Bridges. The durability of specimen met 80% resistant to loss in strength.

Keywords: Metakaolin, Subgrade, Sesquioxide, California bearing ratio, Unconfined compressive strength