Mechanical characteristics of sulfated clay stabilized with colloidal silica considering different number of freeze-thaw cycles

Saturation mechanisms are the cause considerable strength reduction and swelling enhancement in clayey soils. To overcome this phenomenon, stabilization of the weak layers could be useful when any chemical additives which are calcium based are added. In the presence of considerable amounts of sulfate ions, the conventional additive like lime leads to large heaving due to swelling. This paper presents the changes in the amount of California Bearing Ratio (CBR) of soaked samples and swelling index of Najmabad clayey soil after being stabilized with Colloidal Silica (CS). These tests were performed at different curing times of 3, 7, and 28 days. Moreover, CBR tests were performed after Freeze-Thaw (F-T) conditions under 1, 2, 4, 8, and 12 cycles in 3 selected samples which satisfied the required degree of improvement. In addition, free swelling in all the states was measured and controlled. The results revealed fulfilling CBR criterion of samples subjected to F-T cycles and significant reduction of swelling percent in samples with 1% Nano Silica (NS) particles after 28 days curing time and 2% NS particles after 7 days curing time. Also, Scanning Electron Microscopy (SEM) revealed structural changes and an integrated network for soil improved with CS.