An Experimental Study on Geotechnical Properties and Micro-Structure of Expansive Soil Stabilized with Waste Granite Dust

Mining industries around the world produce massive amounts of solid waste that has potential environmental impacts. Therefore, it is necessary to explore alternative solutions to this waste disposal problem and to obtain economic benefits from it. Up to now, no significant attempts have been made to use granite dust (GD) as a soil stabilizer. GD is a by-product produced in large amounts during the cutting and processing of granite rocks at manufacturing factories. Thus, an attempt has been made here to define the role of GD in enhancing the geotechnical behaviour of expansive soil in order to make it suitable for construction. Moreover, the aim of this study is to evaluate the micro-level alterations occurring in the soil to elucidate the stabilization mechanism of granite dust–soil interaction. Comprehensive geotechnical tests, such as Atterberg limits, compaction characteristics, unconfined compressive strength (UCS), California bearing ratio (CBR), and swelling percentage, as well as microstructural analysis, such as X-ray diffraction, scanning electron microscopy, energy, and Fourier transform infrared, have been performed on natural and stabilized expansive soils using different portions of GD ranges from 0% to 30% with an increment of 5%. The results showed that the GD can be effectively used to improve soil plasticity and to control the swelling behaviour. Additionally, the results indicated that both UCS and CBR increase with increasing the content of GD, and that this increase reaches the maximum value at 20% of GD, after which it decreases. Hence, this amount can be taken as the optimum value of GD. The micro-analyses confirmed that the apparent formation of some new peaks, changes in the soil morphology, and alterations in the parent elements are the major factors in controlling the interactive behaviour of soil-GD mixes.