Nanocalcined Clay and Nanolime as Stabilizing Agents for Expansive Clayey Soil: Some Geotechnical Properties

Abstract

Abstract Expansive clayey soils cover wide areas in Syria. Their undesirable properties have caused serious damage to infrastructure. Many attempts have been made to stabilize the expansive clayey soils, most common of which was the use of lime. No detailed work on using calcined expansive clay as a soil stabilizing agent was found in the literature. The objective of this article is to investigate the effect of nanocalcined clay and nanolime on some geotechnical properties of the expansive clayey soil. Three expansive clayey soil specimens quarried from three different sites in the south of Syria have been investigated. They were thermally treated at three different levels (450°C, 650°C, and 850°C) for 3 h. Then, they were ground to have a particle size of less than 100 nm. Three replacement levels of nanocalcined clay were used, i.e., 0, 1, and 2 %. The X-ray diffractometer technique was employed to detect the crystalline and glassy phases in the clayey samples before and after the thermal treatment. Pozzolanic activity of the thermally treated clayey soil was studied using the modified Chapelle test at each of the temperature levels. Atterberg limits, compaction, free swell, swelling pressure, linear shrinkage, and shear strength have particularly been investigated. Test results revealed the positive effect of nanocalcined clay when added to the original soil. Plasticity index was reduced by more than 50 % when 2 % nanocalcined clay was added to the original soil. In addition, 0.6 % nanolime has been added to further investigate the combined effect of nanolime and nanocalcined clay on the properties of the clayey soil. All investigated properties have significantly been improved when nanocalcined clay and nanolime were added together, i.e., swelling pressure and linear shrinkage values were reduced to less than 15 % when compared with those of the original soil.