The Effectiveness of Heated Black Cotton Soil as a Low Calcium Pozzolanic Alumino-silicate Precursor in Lime-activated Stabilization of Black Cotton Soil for Use in Flood Prone Areas

Abstract

The aim of this study was to investigate the effectiveness of heated black cotton soil as a precursor in lime-activated stabilization of black cotton soil in-place for use in flood-prone areas. Most methods used to improve expansive soils include the use of lime or lime-activated materials, cut to spoil followed by replacement and thermal treatment. Most lime treatment methods yield a material that cannot withstand high moisture levels and long flooding periods. Cut to spoil results in high costs and negative environmental consequences. Lime activated Ground Granulated Blast Furnace Slag (GGBS) has been found to be effective in flood conditions, but it has to be locally available. In this study, Unconfined Compressive Strength (UCS) tests were done on 50 mm diameter by 100 mm long stabilized soil specimens using various mixes of heated black cotton soil and lime which established an optimal mix of 14% heated black cotton soil at 400°C and 6% lime as the binders with 80% neat black cotton soil. Investigations of properties of this mix subjected to moist curing periods of 7, 14, 28, and 90 days followed by soaking them in water for 4 and 10 days after each curing period to simulate flash and severe flooding respectively were done. The durability reduction indices for each flooding scenario were computed. The mix yielded a strong durable product able to withstand flooding conditions. The heated black cotton soil at 400°C is, therefore, an effective low calcium aluminosilicate precursor with lime as the alkali activator.