Effect of using Oil Shale Ash on geotechnical properties of cement-stabilized expansive soil for pavement applications

Expansive soil is considered an engineering problem that may cause cracks and distresses in structures and roads. Due to its swelling potential and low unconfined strength, expansive soil causes failures in structures and leads to financial losses. Oil Shale Ash "OSA" is the byproduct of the combustion of the oil shale rock to produce electricity. Instead of dumping OSA materials into landfills, which has several negative environmental implications and cost burdens, utilizing these materials as building materials might alleviate the environmental concerns caused by their disposal. This research investigates the possibility of experimentally using the by-products Oil Shale Ash (OSA) and Portland Cement (PC) to enhance the geotechnical properties of problematic expansive soil. OSA and cement have been added to the soil, where OSA is used in four percentages by dry weight of soil (10%, 20%, 25%, 30%), and cement is used in three percentages (2%, 4%, 6%). A laboratory test program was implemented, including Atterberg limits, compaction test, unconfined compressive strength test (UCS), swell test, linear shrinkage test, and California Bearing Ratio (CBR) test. The results showed that OSA and cement have reduced the expansive natural soil's swelling potential, plasticity index, and linear shrinkage. Also, the UCS and CBR values of treated soil have improved significantly. Pavement analyses demonstrated that OSA-cement-stabilized soil could be a suitable stabilization agent for the subgrade and base layers in constructing pavements.