A Study on the Impact of Wetting-Drying Cycles on Physical and Mechanical Properties of Expansive Soil Treated with Fly Ash: In Case of GEDA Special Economic Zone

Abstract

Expansive soils undergo high volume change due to cyclic swelling and shrinkage behavior during the wet and dry seasons. As a result, when using such problematic soils as subgrade materials or foundation bedding, care should take to avoid them entirely or to treat them appropriately. Previous research on treating expansive soil mostly focused on the improvement of soil but not the durability of such improvements. In this paper, the emphasis laid on the relevance of fly ash, which is from municipal industrial solid waste (MISW) incinerator, suggested as a stabilizing agent for expansive soil. On the native expansive soil and when mixed with 10%, 20%, 30%, and 40% fly ash, tests for particle size analysis, Atterberg limits, free-swell, compaction, California bearing ratio (CBR), and unconfined compressive strength were performed according to ASTM. The findings demonstrate that increment of fly ash decreases plasticity index, Free swell, CBR swell, optimum moisture content (OMC) and maximum dry density (MDD). In reverse, CBR %, and UCS are increased with increasing fly ash content. The greater improvements were shown on 60% expansive soil and 40% fly ash, after the determination of better improvement of soil-fly ash mixture specimens allowed to cure for 7, 14, and 28 days; the maximum result found on 28 days, according to UCS testing. Thus, impact of wetting and drying cycles on physical and mechanical properties of expansive soil improved by 40% fly ash after 28-day curing also studied accordingly. For the cyclic wetting-drying tests, which primarily involve cyclic swelling potential and cyclic strength tests, expansive soil samples from both treated and untreated soil are prepared. According to the results of an experiment, fly ash effectively reduces the swelling potential of expansive soil samples and maintained good strength, which prevents them from collapsing when submerged in water. In contrast, untreated soil samples would collapse when it submerged in water. Samples of expansive soil that have been stabilized with 40% fly ash exhibit sufficient durability in terms of swelling capacity and strength, indicating that both the mechanical and physical characteristics of the expansive soil have been successfully improved.