The focusing in this study was on the contaminated-uncontaminated soils' properties whichstudied by performing experimental tests included, Atterberg’s limit, specific gravity, compaction,unconfined compression, and direct shear tests. Different % of crude oil was used in thecontaminated soils which are performed by mixing the soils using different percent of were oilof 3 %, 6 % and 9 % by dry weight. The main effect of oil contamination causes a reduction in theliquid and plastic limit values for clayey soil. Besides oil contamination gives a reduction in themaximum dry unit weight as well as a decreasing the optimum water content with comparisonto original soil (clayey and sandy soil). The angle of internal friction is decreased for sand whileit increases for clay is one of oil contamination results.
In this study the effect of sodium hydroxide on the strength of clayey soil-cement mixtures was investigated. Clay soils from three various locations of Kirkuk governorate namely Erbil, Laylan and Hawija check points were used. The effect of cement content, curing age, curing temperature and concentration of sodium hydroxide on the strength of soil-cement mixtures were investigated, through carrying out unconfined compressive strength, Triaxial compression and C.B.R tests. It was found that the use of sodium hydroxide markedly improves the strength of soil-cement mixtures. The addition of about 1% of sodium hydroxide by weight of soil could reduce about 5% of cement content by weight of soil required to stabilize the soils effectively.