VING THE GEOTECHNICAL PROPERTIES OF EXPANSIVE SUBGRADE SOIL BY USING EGGSHELL AND PLASTIC WASTE

Abstract

Road failure is a common problem with a series of challenges in Ethiopia. The most likely cause of this failure is expanding soil in the subgrade. In addition, environmental pollution caused by domestic solid waste like eggshells and plastic waste is also a serious problem in Ethiopia that must be addressed. Despite the seriousness of expansive subgrade soil and environmental pollution, problems prevalent in Worabe town, limited investigation and research have been carried out. Therefore, this research was primarily aimed at improving the geotechnical properties of expansive subgrade soil by using eggshell and plastic waste materials that contribute to enhancing the properties of expansive subgrade soils and providing mitigation measures for environmental pollution that are cost-effective and environmentally friendly. Based on index tests, the soil was initially characterized and classified as A-7-5 by AASHTO and CH, MH by USCS systems. To obtain the optimum percentage of each additive, three different proportions of egg shell powder (10%, 15%, and 20% by weight of dry soil) and plastic waste strips cut into 15mm length and 10mm width in (0.3%, 0.6%, and 0.9% by weight of dry soil) were used. The analysis was done by conducting Atterberg limit, compaction, free swelling, and CBR tests. The results showed that increasing the ESP content had a gradual decrease in the PI, and also, it was observed that the curing duration (7, 14 and 28 days) significantly improved the PI. In addition, increasing the ESP content caused a gradual decrease in swelling potential. Moreover, increasing the ESP content increased the MDD and CBR values up to 15%, and then slightly decreased. However, in the case of OMC, the effect is simply the opposite of MDD. The optimum percentage of ESP was found to be 15% ESP based on the MDD and CBR values. On the other hand, an increase in PWS content led to increases in the MDD and CBR values up to 0.6%, and then slightly decreased. However, the OMC effect is just the reverse of MDD. The optimum percentage of PWS was found to be 0.6% PWS based on the MDD and CBR values. Moreover, an increase in PWS content leads to a gradual reduction in swelling potential. In addition to the above, based on the investigated results comparing the effects of ESP and PWS, ESP is more effective than PWS in improving the geotechnical properties of expansive subgrade soil. Cost reduction was seen in both the ESP and PWS stabilization techniques when compared to natural aggregate stabilization.