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Abstract
In the present study, highly expansive clay soils from the Highlands of Ethiopia were studied to evaluate the efficiency of lime treatment to improve their mechanical properties for road subgrades. Soils treated with quick lime at 5, 7 and 9% by dry weight of the soil were cured for seven days under controlled temperature of 40 ± 2 °C and geomechanical laboratory tests were conducted to evaluate its impact on the engineering properties of the soil. Test results show substantial improvements in the properties of the soil after lime treatment. Addition of lime significantly reduces the plasticity index and swelling potential of the soil. Similarly, despite the reduction of optimum proctor dry density due to lime treatment, the unconfined compressive strength and the California bearing ratio show considerable improvements. Based on the current study, expansive soils of the studied area can be effectively stabilised for road subgrade works with the addition of 7% quick lime by dry weight of the soil. For very problematic soil, as the one investigated here, the drastic reduction of swelling potential is of particular interest for a possible application of road subgrade.
Acknowledgement
Our sincere acknowledgement goes to VLIR-UOS Scholarship for the financial support to undertake this study. We also would like to express our gratitude to the Ethiopian Road Construction Corporation, Chancho-Derba-Becho Road Construction Project, Addis Ababa Institute of Technology Laboratory of Geotechnics and Central Geophysical Laboratory of Ethiopia. Our especial thank also goes to Tekalign Asrat, Yonas Asres, Nicolas Canu and Jan Van der Perre for their diligent help and caring.