Effect of low calcium fly ash (ASTM class f) on the stabilization behaviour of expansive soil

Expansive soil experiences swelling with the addition of water and then shrink after the removal of water. These alternate wetting and drying impose lot of problems to the structures built on expansive soils. Ground improvement techniques for expansive soil include chemical and mechanical method of soil stabilization. In this paper, chemical stabilization has been used as a ground improvement technique. Testing such as compaction, unconfined compressive strength (UCS) and swell pressure were conducted for expansive soil stabilized with ASTM Class F fly ash as a chemical stabilizer at 8%, 16% and 24% of total weight. Based on the outcome of this study, it was noticed that maximum dry density (MDD) increases up to 16% and then decreases beyond that. Effect of fly ash on variation of UCS value was observed with three different curing periods (7, 28 and 45 days) as well as three different percentages of fly ash (8%, 16%, 24%). UCS values increase up to 16% and then they decrease with any further addition of fly ash. Further, increment of curing period helps to increase the UCS value for a given percentage of fly ash mixture. Reduction of swell pressure was observed with addition of fly ash. On the whole, fly ash can be successfully used as soil stabilized to improve the geotechnical engineering properties of expansive soil