Evaluation of the uniaxial compression strength and Atterberg limits of metakaolin-treated sandy clay soil

Improvement of poor soils as an inevitable issue plays an important role in civil engineering projects. In this paper, the effect of adding metakaolin on Atterberg limits and uniaxial compressive strength of sandy clay soil was investigated. For this purpose, uniaxial compressive strength tests have been done on non-stabilized and stabilized soil samples with 5, 10, 15, 20 and 25% of metakaolin at curing times including immediately after mixing, as well as 7, 14 and 28 days. The Atterberg limits test have been also conducted on stabilized soil samples with 5, 15 and 25 at immediately after mixing. The results show that increasing the percentage of metakaolin increases the liquid and plasticity limits of sandy clay. So that the amount of plasticity limit of soil is less than the liquidity and thus the soil plasticity index increase. Stabilized samples with 25% metakaolin increased by 1.33 and 1.40 times, respectively, for liquid and plasticity limits, due to the highest change in the Atterberg limits of sandy clay soil. The study of stabilized soil in plasticity chart shows that by adding of metakaolin, the soil's position in this chart is negligible. Also, increasing the percentage of metakaolin and the curing time increases uniaxial compressive strength of the sandy clay. The highest strength rate for 25% of metakaolin occurred at 28 days. Also, studying the failure planes and the failure rate of the tested specimens shows that with increasing metakaolin, the failure of the specimens occurs faster after reaching the final strength.