Comparative Study of Geotechnical Properties of Fly Ash and Bio Soil Mixed with Low Plastic Clay

Abstract

Bio soil is a byproduct obtained from the biomining of legacy waste, which typically contains over 50% of this inert material. Currently, its primary applications are limited to agriculture and filling low-lying areas. However, since bio soil is considered a waste material, this study explores its potential use in geotechnical structures, particularly as a subgrade material for highways. Fly ash is commonly used as a filling or subgrade material in highways and expressways. This research investigates whether bio soil can serve a similar purpose. For designing subgrades, the California Bearing Ratio (CBR) and compaction characteristics are crucial properties. This study compares the geotechnical properties of fly ash with those of a mixture of bio soil and low plastic clay. Laboratory tests were conducted to evaluate the compaction characteristics and CBR values of the bio soil-clay mixtures, focusing on the effect of different mixing ratios on strength improvement. Proctor compaction tests were used to analyze the compaction behavior, while CBR tests were conducted to assess strength characteristics. The study examined the impact of adding varying proportions of low plastic clay (0%, 20%, 40%, 60%, and 80%) to bio soil. Results showed that the optimal improvement in CBR and Maximum Dry Density (MDD) was achieved with a 60:40 ratio of bio soil to clay when compared to fly ash. Consequently, the findings suggest that bio soil, despite being a waste product, can be effectively utilized as a subgrade material in highways when mixed with low plastic clay.