Using nano-cement for the improvement of clayey soils affected by municipal leachate
Ahmad Rafiei, Hadi Ahmadi, Payam Zanganeh Ranjbar
Abstract
The use of nano-materials as a stabilizing agent in soils has a significant role, particularly in improving their mechanical properties. This study investigates the impact of stabilization using nano-materials, specifically nano-cement, on natural and contaminated clays. A series of laboratory tests, including Atterberg limits, compaction, unconfined compressive strength, permeability, and consolidation, are conducted to evaluate the soil properties. Various percentages of nano-cement (0 %, 0.5 %, 1 %, 1.5 %, and 2 %) are added to two sample groups; one prepared with water and the other with leachate. Based on the results of Atterberg limits tests, adding 2 % nano-cement to natural clay increases the liquid limit by 8.6 % and decreases the plasticity index by 16 %. These values diminish to 8.3 % and 13 % for contaminated clay. Furthermore, according to the compaction test results, increasing nano-cement content by up to 2 % leads to a reduction in maximum dry density by about 11.5 % and an increase in optimum moisture content by about 15.9 %. However, these values change to 5.77 % and 32.25 % for contaminated clay. The results indicate that increasing nano-cement content generally improves the strength and stiffness of the soil while reducing its permeability. On the other hand, contamination of the soil leads to a reduction in strength and stiffness, while permeability increases. Based on the Field Emission Scanning Electron Microscopy (FESEM) analysis, the incorporation of nano-cement improved the microstructure by decreasing pore spaces and enhancing bonding between particles. While chemical complexity of leachate negatively affects nano-cement dispersion, which leads to increased particle aggregation.