Improving the geotechnical properties of medium expansive clay using various gradations and percentages of glass

Significant amounts of waste glass are deposited each year, which poses a significant environmental problem globally. Utilizing waste glass for soil improvement has emerged as an environmentally friendly solution, attracting increased research interest in recent years. This study investigated the effects of waste glass gradation and content ratios on the compaction, strength, and swelling characteristics of medium expansive clayey soil and pulverized glass mixtures. Waste glass was crushed into three different size gradations and mixed with the soil at eight different weight ratios (0%, 4%, 8%, 12%, 16%, 24%, 32%, and 40%). Standard Proctor compaction and unsoaked and soaked California Bearing Ratio (CBR) tests, along with swelling tests, were conducted on each sample. Microstructural analysis was performed through scanning electron microscopy (SEM). The results indicated that adding up to 40% pulverized waste glass reduced the Optimum Moisture Content (OMC), whereas the Maximum Dry Density (MDD) increased. Moreover, the unsoaked and soaked CBR values increased notably with higher pulverized glass ratios. Increases in unsoaked CBR values reached up to 143.5%, 129.8%, and 122.1% for coarse, medium, and fine pulverized glass grades respectively, while those for soaked CBR were 209.2%, 197.2%, and 189.4% respectively. Additionally, the swelling percentage decreased as the pulverized glass content increased. The different grades of pulverized glass showed no significant effect on the swelling percentage at glass contents up to 8%. Statistical analysis revealed strong correlations between the tested parameters. Relationships between the soaked and unsoaked CBR values derived from OMC, MDD, and waste glass ratio were also discussed.