This paper discusses the use of non-freshwater, including brackish groundwater and oily production water, in road construction. Non-freshwater was obtained from four major oil production fields in Oman. First, chemical analyses were carried out on nine non-freshwater types, including tap water, obtained from the four sites. These water types were then used with well-graded sand (WGS), high-plasticity silt (HPS), and a road base material to evaluate water effect on material properties. Atterberg limits, compaction, California Bearing Ratio (CBR), swell percentage, swell pressure, and direct shear tests were performed. Results show that there is a slight decrease in the liquid limit when non-freshwater is used. Non-freshwater resulted in a slight decrease in optimum moisture content and a slight increase in maximum dry density in WGS, whereas with HPS it caused slight decreases in optimum moisture content and maximum dry density values. There was an increase in CBR when non-freshwater was used with WGS and HPS soils. However, the use of production water caused a decrease in CBR values for WGS. For the road base material, the use of non-freshwater generally caused a decrease in CBR. The swell pressure tends to increase when non-freshwater is used with HPS. For the road base material, there is a decrease in cohesion and an increase in friction angle when non-freshwater is used in lieu of tap water. Promising laboratory results indicate the potential use of brackish and oily water types in road construction.
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