Soil Stabilization Using Natural Pozzolana for Cost-Effective Road Pavement Construction in Tanzania'

Recent works of research in Civil Engineering Sciences have noted with delight the significant role that subgrade plays in safe and cost-effective pavement construction projects and design in developing countries. Given that the materials used are durable, there is an increasing requirement/awareness for the improvement of both the plasticity and the bearing capacity of local existing soils especially in Dar es Salaam, Tanzania. Laterite soil is a residual soil that is noted for being soft when excluded from air and rapid hardening when exposed to air with high resistance to water and air penetration. Due to a series of wetting and drying processes over time, vertical movements in the soil mass can occur, leading to pavement failures such as settlement, cracking, and unevenness. This results in the collapse of the infrastructure project that is built or supported. Also, the scarcity of the utilization of crushed rock (CRR) and crushed stone (CRS) as base course materials for road pavement construction constitutes a problem in some locations within Tanzania due to the far location of the quarry site and the overall transportation and material costs. Laterite soil is therefore noted as one of the local materials that are readily available in large quantities in some areas. However, due to the fact that this type of soil has low strength for road base construction because it exhibits certain unique properties of thermal and mechanical instabilities that make it different from other road construction materials, not much attention is paid to it. Hence this research and the question: How can Natural Pozzolana through experiments be improved upon for soil stabilization in road and infrastructure projects in Tanzania? National Statistical figures show that Tanzania imports about 40,000 tons of fly ash on an annual average in the construction sectors. The use of pozzolana for soil stabilization will sustainably reduce the costs of these importations. The objective of this research is to determine how this can be carried out using the collected natural laterite soil after stabilization using Sieve analysis, Compaction test, Atterberg limit test and California Bearing tests in the Central Material Laboratory (CML).