Performance of Lateritic Soils Stabilized With Both Crushed Rock Aggregates and Carbon Black as a Pavement Base Layer

Abstract

The increased crushed rock aggregate consumption resulting from road construction has greatly contributed to the depletion of national rocks in Uganda, hence environmental degradation. The purpose of this study was therefore to investigate the use of carbon black in reduction on the amount of crushed rock aggregates used in mechanical stabilization of unsuitable lateritic soils for road base construction. Preliminary tests on the lateritic soil were carried out to determine if the soil required stabilization. The test results classified the soil as Clayey Gravel with Sand of high plasticity based on the Unified. Soil Classification System (USCS) and it required stabilization for use on road base. The combined effect of carbon black and crushed rock aggregates was investigated based on the compaction characteristics, Atterberg Limits, Particle size distribution and California Bearing Ratio tests. Results obtained were analyzed graphically and a blend of 50% lateritic soil, 40% aggregates and 10% carbon black was found to be the most effective in producing a suitable base material. It gave a CBR of 69.4 at 95% relative compaction and a plasticity index of 7 which meet the requirements of CBR above 60% as per the General Specifications for Road and Bridges (2004) of the Ministry of Works, Housing and Communication in Uganda. In relation to previous research, by Jjuuko et al. (2014) which recommended 50% aggregates and 50% lateritic soil, there is a 10% reduction in crushed rock aggregate consumption.