Utilization of Glass Cullet As an Admixture to Cement Stabilized Black Cotton Soil

Abstract

Expansive soils such as black cotton soil (BCS) are a serious challenge in engineering construction owing to their heaving and shrinkage behaviour. Many techniques are used around the world to improve their engineering properties among which are soil modification and stabilization. This paper presents the efficacy of glass cullet (GC) when used in a mixture with cement for stabilization of BCS. Laboratory tests were conducted in accordance with the British Standards BS 1924-2:1990 on the BCS treated with 0, 2, 4, 6, and 8% ordinary Portland cement (OPC) as well as 0, 5, 10, 15 and 20% GC. The soil is categorised as A-7-5(17) based on the American Association of State Highway and Transportation Officials and CH agreeing to the Cohesive Soil Classification Scheme. Unconfined compressive strength and California Bearing Ratio tests were conducted using the British Standard Light (BSL) and British Standard Heavy (BSH) compactive efforts. The curing periods used were 7, 14, and 28 days. There was a significant improvement on the engineering properties of the soil. There was a decrease in plasticity characteristics and an increase in maximum dry density with increasing GC content for all cement proportions used and also for GC alone. The maximum UCS values of 1152 kN/m2 and 1568 kN/m2 for BSL and BSH were respectively obtained after 7 days curing. These are, however, much lower than the recommended value of 1720 kN/m2 for base course by the Nigerian General Specification (1997). The maximum CBR values of 53.8% and 63% were obtained for BSL and BSH compactive efforts corresponding to the blend containing 8% OPC and 5% GC. More importantly, with an 8% OPC content, all samples containing GC from 5% to 20% satisfied the sub-base requirements by the above specifications. The Specification of 30% CBR criterion for sub-base was achieved. BCS treated partially with OPC and GC within that range is therefore recommended for use as sub-base and subgrade materials for road pavement construction.