Utilisation of Phosphogypusm and Flyash in Soil Stabilisation

Background/Objectives: Buildable land with good natural bearing capacity is reducing and it leads to the construction of buildings on poor soils which are finally leads to structural foundation failures. This necessitated the use of available admixtures for the improvement of soil characteristics economically. Among the available resources, industrial by- products can be effectively used as admixtures since it can solve the hazardous problems due to its disposal. Methods: Grain size analysis and Atterberg’s limits tests are conducted to classify the soils used in this study. To evaluate the effect of admixtures, strengths characteristics of soils were observed by Unconfined Compressive Strength and California Bearing Ratio tests. Weak soils having high expansive characteristics are used to study the activation of 5% fly ash blended with Phospho Gypsum (PG) at varying percentages of 2%, 4% and 6% with two weak soils at different curing conditions. Findings: Results shows higher strength development upto a percentage of 4% PG with 5% flyash with both the soils. Effect of curing periods on strength characteristics of treated soils at 7, 28 and 60 days were also considered in this study. Microstructural studies are also showing an improvement in microstructure which is examined in SEM micrographs and XRD results. The influence of flyash with different percentages of phosphogypsum on swelling characteristics shows a decrease in swell potential of treated soil with increase in curing periods. Improvement: This study gives an effective application of Phospho Gypsum and Fly Ash in geotechnical field by using it as a relevant soil stabilizer. Increase in CBR values were obtained with Fly Ash and Phospho Gypsum combinations with soils, which reduces the thickness of pavement and making more productive use of industrial wastes with considerable environmental benefits.