EVALUATION OF SALT WATER EFFECT ON THE PHYSICAL PROPERTIES AND COMPACTION CHARACTERISTICS OF EXPANSIVE SOIL

Expansive soils pose a significant hazard to civil engineering structures due to its high swelling and shrinkage potential. There are many techniques available to reduce the effect of volume change of expansive soil due to change in water content within the soil mass. Soil stabilization by mixing various chemical additives has been proved to be effective alternative solution to overcome the undesirable swell. The objective of present study is to determine and evaluate the effect of addition of chloride salts on expansive soil in term of change in index properties and swelling characteristics.In this study, an experimental program developed to investigate the effect of salt water on the engineering properties of high swelling clays. The laboratory tests were carried out in the soil mechanics laboratory of Al Azhar University and central laboratories of Arab Contractors. The materials used in this research were silty clay obtained from Bait El Watan project, western of Suez road in New Cairo city, tap water as well as saline water, which is obtained from mixing of salts and distilled water at various concentrations (5, 10,20,30,50 and 60%) as an effective chemical stabilizer in expansive soils. However, the results showed a remarkable decrease in liquid limit by 47.8 percent. Plastic limit also showed a continuous decrease with increasing salt concentration to reach 6.2% decrease at 60% salt concentration. Compaction properties also significantly improved in presence of salty water as the maximum dry density increased from 17.83kn/m3 to 18.95 kn/m3 at salt concentration of 60%, with a corresponding decrease from 15.6% to 12% in optimum moisture content. Free swell index reached a maximum decrease of 21.7% at a salt concentration of 30%, as it decreased from 66.65% to 56.8 %. Results of Oedometer test also revealed an improve of swelling properties of expansive clay soil expressed by a decrease in swelling heave from 5.61 for samples mixed with fresh water to 4.3 mm when mixed with 30% salt concentration with a rate of reduction 23.4%.