Chemical influence of nano-magnesium-oxide on properties of soft subgrade soil

Abstract

Improving the properties of soft subgrade soils greatly helps in construction of strong and economical pavements. For this purpose, there are many traditional additives. However, these are often expensive and their production causes consumption of large amounts of energy and increases environmental pollution. Therefore, this study suggests the use of a modern alternative, nano-Magnesium-Oxide. In this study, soil from Baghdad city was selected and treated using different doses of the proposed additive namely )0.20, 0.40, 0.60, 0.80, 1.00, 1.20, 1.40, 1.60, 1.80, and 2.00) % by weight of dry soil to study the changes in its engineering properties. The study included conducting laboratory tests to compare the soil properties before and after treatment. These include the California Bearing Ratio Test (CBR) and measuring the swelling ratio to determine the changes in engineering properties and to determine the optimum dose. Thereafter, an Energy-Dispersive X-Ray Spectroscopy (EDXR- Spectroscopy) test was performed to determine the chemical reactions that contributed in changing of soil properties. The results showed noticeable improvement in the properties of the soil. CBR value of the soil treated with optimum dose (which is 0.80%) increased to about 1200% of its value for original soil. Moreover, swelling ratio of the soil treated with optimum dose decreased to about 10% of that recorded in original soil. EDXR- Spectroscopy tests exhibited the presence of influential chemical reactions between the additive and the soil that may create Magnesium Silicate Hydrate which formed strong bonds between the soil particles increased its tightness.