Experimental Study on Strength Behaviour of Expansive Soil Treated with Phosphogypsum and Wood Ash

Developing countries like India focus their attention on the development of infrastructure like railways, roadways, airways and housing facilities. The stability of the structures to be built on the soil depends totally on the stability of the soil at which it rests. There are several soils that pose threat to the stability of the structures built on them. Expansive soil is one such problematic soil, widely spread across the world. Researchers have focused more on the use of potentially cost effective materials that are locally available from industrial and agricultural wastes to improve the properties of expansive soils. In this study the potential of two waste materials- wood ash (WA) and phosphogypsum (PG) to stabilize problematic clay soil samples were evaluated. Wood ash is the residue left after burning of woodand phosphogypsum is a waste by product obtained from the fertilizer industry. The effect of varying percentage of wood ash on the strength properties of two expansive soil samples stabilized with 4 % phosphogypsum is presented. Strength characteristics of virgin soil samples as well as soil mixed with 4 % phosphogypsum and 8 %, 10 %, 12 % and 14 % of wood ash respectively were found by UCC and CBR tests. The test results showed maximum strength of the soil samples when treated with 4 % phosphogypsum and 12 % wood ash. The use of two waste by-products, phosphogypsum and wood ash may serve as an effective and efficient way to stabilise the soil and minimise disposal problem caused by the waste materials.