Sustainable Techniques for Improvement of Black Cotton Soils

Soil is the most significant natural building material. It is a complex phenomenon consisting of soil solids, water, air, and organisms in different proportions. Soil is not only a critical resource that nourishes and preserves life on earth, but it also acts as a foundation for all civil engineering structures. The strength and stability of these structures depend on the capacity of the soil to withstand loads and offer a stable foundation. Understanding the characteristics of soil and its behaviour is therefore essential to confirming the sustainability and safety of any building project. Soil property significantly impacts construction costs and safety. Black cotton (BC) soils, a type of expansive clay with undesirable properties that fluctuate in volume due to water content changes, are also crucial in the construction industry. Black cotton soil areas, which have a dark brown colour and are suited for the cultivation of cotton, are mostly found in India’s Deccan Trap. They lack nitrogen, phosphoric acid, and organic matter but are high in calcium, potassium, and magnesium. They are unsuitable for building or engineering structures. It contains montmorrilonite, illite, kaolinite, iron oxide, calcium carbonate, and organic matter, with swelling and shrinkage primarily due to aluminum and magnesium silicates. Black cotton soils pose challenges for engineers globally, particularly in tropical countries like India, due to temperature and moisture variations. They are of a high expansive nature, highly compressible, have poor drainage capabilities, and have low load-bearing capacity, causing consolidation settlements, swelling, and shrinkage. These issues can cause structures to lift up and crack during dry seasons and cause settlement and shrinkage cracks. Many studies investigated different techniques and materials for improving black cotton soil, which were also tested in laboratories. The primary goal of this study is to investigate potential sustainable materials and techniques for enhancing black cotton soil so that black cotton soil zones could potentially be used for building and infrastructure development while maintaining stability and safety. Xanthan gum, a natural adhesive, and terrazyme, a natural liquid enzyme, were also used to enhance soil. The characterization of black cotton soil in Kolhapur, Maharashtra, India, has been done. Soil from 4.0 m below ground level was mixed with xanthan gum and terrazyme after being sampled up to a depth of 4.75 m in four separate layers. The potential of xanthan gum and terrazyme for enhancing black cotton soil with a high proportion of silt and clay was investigated. Xanthan gum was combined with various percentages of soil, and terrazyme doses were given per 100 ml of water. The results revealed that both additions increased the unconfined compression strength. These two compounds are non-toxic and may be used to effectively enhance black cotton soil.