Soil Stabilization Experimentation with Natura l Pozzolana for Cost Effective Road Construction Projects in Tanzania

Abstract

Subgrade plays an important role in safe and cost-effective pavement construction, given that the materials are suitable but there is a requirement for improvement of both the plasticity and the bearing capacity of local existing soils especially in Dar es Salaam. Laterite soil is a residual soil that has a tendency of being soft when excluded from air and rapid hardening when exposed in air with high resistance to water and air penetration. As a result of wetting and drying process, vertical movements take place in the soil mass that leads to failure of pavement in the form of settlement, cracking and unevenness. Also, the scarcity of the utilization of crushed rock (CRR) and crushed stone (CRS) as base courses material for road pavement construction constitute a problem in some location within Tanzania due to the far location of quarry site and the overall transportation and material costs. Laterite soil is one of the local materials available in some areas, but this type of soil has low strength for road base construction since it exhibits certain unique properties of thermal and mechanical instabilities that make them different from other road construction materials.  This often results to their tests results not conforming to conventional specifications requirements and the materials being rejected for use due to much poorer gradings than the local residual granitic gravels such as crushed rock CRR, despite performing very well when used in roads. Statistically, Tanzania reportedly imports about 40,000 tons of fly ash on annual average in the construction sectors. Soil stabilization will go a long way to reduce costs of these importation. The objective of this research is to determine the laterite soil properties after stabilization and the research question is how can we use the natural pozollana to stabilize soil as a solution to the problems created by these soils in construction?

Keywords: Soil stabilization, Pozollana, cost effective construction, local material, Tanzania

DOI: 10.7176/CER/15-3-02

Publication date:August 31^st 2023