CHAPTER ONE

1.0                                               INTRODUCTION
Soil is the cheapest and the most widely used material in civil engineering project as foundation material either in its natural or improved form. It is highly heterogeneous and an isotopic in nature and existing with different engineering properties which can be influenced to some extend by the presence of sodium salts under the influences of water (Olawale, 2013).
       The properties of soil as an engineering material depend on its surface electric charges, chemical composition, shape and size. The chemical composition influences to exhibit enormous change in the engineering properties especially in soil with high content of clay materials (Olawale, 2013).
Lateritic soil is one of the commonest materials that are widely used in the construction of civil engineering infrastructures, such earth dams, covers and pavement is constructed in layers in Nigeria, and surfacing. The first three layers are mostly constructed using laterite soil depending on the expected traffic volume and intensity suitability on the soil in terms of specification (Agbode and Osunolalo and FMN, 1997).
Transportation geo-environmental is a new emerging area that is interdisciplinary in nature. It cut across transportation, geotechnical and environment engineering, and aim at analyzing, predicting and solving problem of soil that are affected by environmental factors (Olawale, 2013).
The study of the effects of soluble salts in soil found out that chloride, sulphate and nirate of sodium increases the permeability of the soil, since there is clear indication that permeability; one of the engineering properties of soil is affected by the presented of the salts, it is pertinent to investigate their effect on the wider properties of the soil (Olawole, 2013).
    The investigation made on the effect of sodium sulphate water on the mixed with clay soil, the result indicate there was increase in optimum moisture content and decrease in maximum dry density (Sherwood, 1992)
    The effect of sulphate salt on engineering properties of lateritic soil was examined and the finding shows the maximum dry density and specific gravity decrease with tine while optimum moisture content increase with time (Sherwood, 1992)
    The research is aimed at evaluating the effect of salt contamination on the engineering properties of soil using hydrated sodium (ii) tetraoxosulphate (iv) salt (NaSO4).
1.1          STATEMENT OF THE PROBLEM
The effect of sodium sulphate contamination on engineering properties of lateritic soil causes failure to  highway pavement in existing roads and make highway foundation materials to be unsuiltable for highway construction.
1.2    AIM AND OBJECTIVES OF THE STUDY
    Access the actual performance of lateritic soil when contaminated with sodium (ii) tetraoxosulphate (iv) salt (NaSO4)
    To identify and appraise NaSO4 as a contaminant on lateritic soil.
    To show the effect of the NaSO4 on various engineering properties of lateritic soil.
    To evaluate the strength of lateritic soil when contaminated sodium (ii) tetraoxosulphate (iv) salt (NaSO4) and when free from the contaminant.