Bituminous stabilization of clay soils for road construction

Thesis Abstract

The rate at which roads fail in Nigeria should worry any responsible citizen. Considering the enormous resource expended to construct a kilometer of road, it is heart breaking when the same road fail barely six (6) months after construction. For in the life of our dear country, the all important economic theory of opportunity cost is applicable just as it is elsewhere in the world. Stabilization is a viable alternative to achieving a durable road construction regime. Soil stabilization is not new, even in this part of the world, but as dynamic as the world is, more cost effective and less problematic means of stabilization is being researched or reviewed daily. Bitumen stabilized materials (BSM) either as subgrade or road base is still new or nonexistent in this part of the world. In some part of Africa especially Southern Africa it is already in use to construct rural roads without any further surfacing. The cohesion between the bitumen and the soil particles brings about a decrease in moisture and an increase in density and ultimately results in a durable road. For this research, soil sample was obtained from a supposed problematic soil along KM 105 Port Harcourt –Aba, expressway, Umuahia. The soil was analysed for Atterberg’s limits, compaction (moisture-density relationship) and California bearing ratio at 6%, bitumen content. It was analyzed for compaction and CBR again to compare with the result obtained prior to stabilization. A further stabilization was done with 8% bitumen content and another with 10% bitumen content and in both cases moisture-density test and CBR test performed. The results showed a significant positive improvement in the index properties of the soil, but also showed a decline in CBR value as the bitumen content increased from 6% to 10%. Thus there was need to get the optimum quantity, and so I had to carry out same procedure this time with 2% and 4% bitumen content and the results showed 4% bitumen content as the optimum.