Experimental Study on Nano SiO₂ and Cement Modified Expansive Soil

Abstract

An experimental study was performed to determine the effect of adding nano SiO₂ and cement to modify expansive soil. In order to get the basic properties of the soil, some soil tests were carried out to determine the basic physical properties. Also, SEM, XRD and Unconfined compression test were carried out to identify the underlying mechanisms. The test results of soil liquid limit and plastic limit1 classified soil as a medium expansive soil. The optimal water content and the maximum dry density is 24.6% and 1.47 g/cm³ respectively. The final average swelling ratio of two groups of expansive soil is 35%. Unconfined compression test is the ultimate strength of the soil sample under the condition of lateral restraint, experimental data showed that after adding 4% cement + 1% SiO₂, and 3% cement + 2% nano SiO₂, failure strength were 4326 kPa and 1400 kPa, respectively. XDR test data indicates that the major mineral in the soil is kaolinite, montmorrilonite, and dolomite. After modification, a new peak is incorporated which indicates the hydration products of cement-calcium-silica gel. While XRD patterns for the 4% cement + 1% nano silica and 3% cement + 2% nano silica modified soils are basically the same, but the intensity is not the same, which is consistent with the different amount of admixture. For the SEM image of soil samples with 4% cement and 1% nano silica soil, in comparison with the expansive soil and cement treatment soil, more dense soil surface structure was observed.