Plasticity Characteristics of Ferrock Reinforced Expansive Soils
The rapid growth in urbanization and the major development of metropolitan cities is leading to a rapid shift of population from rural to urban regions. This is having a tremendous impact, leading to rapid growth of constructional activities. Further, due to lack of good sites available for construction, it is forcing the construction industries to use marginal lands and lands considered unsuitable for construction, such lands are largely made up of problematic soil (expansive soil). Expansive soils due to their swelling and shrinkage behavior make the construction difficult and need periodic maintenance which increases the overall life cycle cost of structure. And with nearly 657,452.6 km2 area in India being covered with expansive soil, it is imperative to find a cost effective solution for improving engineering behavior as well as reducing cost of construction. It is observed that the engineering behavior of fine-grained soils mainly depends on the magnitude of clay minerals present in it i.e., kaolinite (least active clay mineral), montmorillonite (most active clay mineral) in different proportions. The soils which are having expansive behavior are predominantly enriched by montmorillonitic clay mineral. The plasticity characteristics of montmorillonitic soils like Liquid limit vary significantly. In order to understand physicochemical phenomena of expansive soils many researchers in the past have made several attempts to understand the engineering behavior in particular with plasticity characteristics. It is seldom observed that most of the studies related to expansive soils are region specific. Ferrock, a carbon negative material which is produced by recycling waste materials such as waste steel dust from steel industries and fly ash from thermal plants is used to treat expansive soil. No information is available in documented literature on use of a new and alternative material Ferrock in soil stabilization, invented by Dr. David Stone in 2017. In the present experimental research study a detailed study of index properties of plain expansive soil and soil stabilized with Ferrock have been carried out. An attempt has been made to study the plasticity behavior of three natural field expansive soils having a wide range of Liquid limit (55%-75%) with that of same soils treated with different proportions of Ferrock. It is also intended to stabilize the expansive soil having wide range of liquid limits varying from 55%-75% which exactly represent field conditions. Free swell ratio, free swell index and swell pressure tests were carried out to assess the swelling potential of Ferrock stabilized black cotton soil. The natural field soils were treated with varying proportions of Ferrock in order to determine a stable mix proportion. The degree of expansion of expansive soils were analyzed. Unique and very useful correlations were established between the percent fines and plasticity characteristics. A new plasticity chart was developed for the classification purpose. It is observed that by reinforcing the montmorollinitic soils with Ferrock the intensity of free swell ratio, Liquid limit can be reduced reasonably and thereby increasing the plastic limit and shrinkage limit which greatly influences the engineering behavior of soil. This innovative project is eco-friendly and provides an economical solution in overall development of infrastructural facilities by using industrial waste materials which otherwise reach landfill.