Soil Stabilisation Using Phosphogypsum and Flyash

Abstract

Since ancient times, a number of stabilization methods are being used to improve soil properties. Various studies have been carried out on expansive soil after stabilization with additives such as cement, lime, cement kiln dust, rice husk ash etc. which shown promising results. Now-a-days easily available industrial by-products are used for the enrichment of soil properties. In present study, effects of stabilizing agents like Phosphogypsum (PG) and Flyash (FA) have been studied for strength improvement in varying percentages. This paper describes a study carried out to check the improvements in the properties of soil with phosphogypsum in various percentages (i.e., 2, 4 and 6%) with fixed quantity of flyash (5%). The unconfined compression test (UCC) and microstructure analysis of the soil with different percentage of additives were determined separately after curing the specimens for 3 days and 7 days. Strength of stabilised soil is increase with increased amount of stabiliser and curing periods. Expansive soils were been a tough task for Civil Engineers in the design and construction of Infrastructure projects. The major problems with clays, including low strength and high compressibility, can cause severe damage to civil engineering structures and can lead to very serious economic loss and environmental hazards. Therefore, these soils must be treated before commencing the construction operation to achieve desired properties. This has led to the development of soil stabilization techniques. Since the nature and properties of natural soil vary widely, a suitable stabilization technique has to be adopted for a particular situation after considering the soil properties. The chemical technique is a common soil stabilization approach, since it produces a better quality soil with higher strength and durability than mechanical and physical techniques. In many countries of the world, stabilization of soils is especially done if locally available natural/industrial resources are available. The use of Phosphogypsum (PG) and Flyash (FA) in soil stabilization can lead to low-cost construction and can provide an environmentally friendly means of their disposal and also enhance the engineering properties of soil. Phosphogypsum is a by-product in the wet process for manufacture of phosphoric acid (ammonium phosphate fertilizer) by the action of sulphuric acid on the rock phosphate. Flyash is one of the residues generated during the combustion of pulverized coal and is transported from the combustion chamber by exhaust gases. Flyash is mainly used as stabilizer considering its construction potential as a pozzolanic material. In this paper, the study is aimed to investigate the strength and the microstructure of treated clay using unconfined compressive strength test and scanning electron microscope (SEM) analysis. II. LITERATURE REVIEW