Comprehensive Microstructural and Shear Behavior Analysis of Lime- and Nano-Alumina-Stabilized Clay Using Non-Destructive Techniques

Direct shear tests and ultrasonic pulse velocity (UPV) tests and SEM, AFM and XRD microstructure were conducted to investigate the shearing properties and microstructure of CH clay soils stabilized with various contents of nano-Al₂O₃ and lime at different curing times. The direct shear test results show that for a constant normal stress, increasing the lime content increases the shear strength of the soil. On the other hand, the shear strength of soil stabilized with 9% lime at a normal stress of 200 kPa increases to 32% due to the addition of 1.2% nano-Al₂O₃ (optimum content). Increasing the content of nano-Al₂O₃ more than the optimum content (1.4%) causes a decrease in shear strength by 4% compared to 1.2% of nano-Al₂O₃. Also, adding nano-Al₂O₃ up to the optimum content of 1.2% increases the internal friction angle and cohesion. The SEM images of the sample containing 1.2% nano-Al₂O₃ show a dense microstructure without voids and with much of the sample comprising high-strength CAH gel. Also, AFM images show that the addition of 1.2% nano-Al₂O₃ compared to the sample without nano-Al₂O₃ reduces the surface roughness. The results of XRD tests show that for the sample stabilized with 1.2% nano-Al₂O₃, the intensity value corresponding to CAH gel is 2340. Meanwhile, in the sample without nano-Al₂O₃, the intensity value corresponding to CAH gel equals 1597. Also, the peak intensity of calcium hydroxide crystals for the sample without nano-Al₂O₃ equals 1382 and 1516.