DOI: 10.14457/tu.the.2018.948
title: Strength and durability assessment of bottom ash and lime stabilized clayey soil as a sustainable road material in Thailand

description: Tropical climatic countries like Thailand, Malaysia, Singapore have a high frequency of rainfall. Such high rainfall is one of the leading causes of many flood cases in Thailand. Bangkok clay found in Thailand, has a high plasticity index that increases with depth and swells when in contact with water are characteristics of this clay. This can result in differential settlement of structures along with other issues. Therefore, stabilization of Bangkok clay is necessary before performing any construction work above it, especially road pavement construction. Since floods have a direct effect on the roads roads with undesirable soil must be stabilized before allowing vehicles to run above them considering the heavy rainfall. Soil stabilization using various materials like Cement, Lime, Rice Husk Ash, Polymers, Palm Oil Fuel Ash, Bottom Ash have been reported in previous researches done. Fly ash and bottom ash are the byproducts from coal power generation. Fly ash has been utilized in the concrete industry as well as in the geotechnical improvement of soil properties. On the other hand, bottom ash because of heavier weight, porous and coarse-grained structure is generally neglected and dumped in the environment. This dumping has given rise to various environmental issues like air pollution, groundwater pollution, etc. Therefore, it is beneficial to be utilized for some other purpose to minimize such environmental hazards. Based on the report provided by EGAT about 0.8 million tons per year of bottom ash is produced in Thailand, which is about 20% of total ash production. So, the excess bottom ash must be utilized. Therefore, it has been considered as one of the materials used for this study. However, bottom ash is found not to satisfy the requirement as a binding material because of the lack of proper amount of free lime in it. Therefore, additional cementing material is required to provide some bonding to the new material formed after mixing bottom ash and soil. Lime is reported to form good cementing material in contact with soil rich in silica and presence of water. Hence, it has been considered as a binding material for our study.For this research the tests like particle size distribution, specific gravity, compaction, UCS, durability and permeability tests were performed with different combination of Bangkok clay, bottom ash and lime. The UCS test was performed with 20 different combination of the materials used and 4 different curing periods namely 1, 7,28 and 56 days. The results showed improvement in strength with stabilization of soil with bottom ash and lime. 50% bottom ash and 12% lime content were found to be the optimum mix design with respect to strength. For durability test, the specimens were subjected to wetting drying cycles. However, two conditions of soaking i.e., capillary soaking and complete soaking were used. The specimens resulted in durability on performing soaking and drying and 50% bottom ash and 12% lime showed optimum durability in terms of strength. The morphology and chemical characteristics of the materials were also analyzed through SEM and XRF tests. The SEM test also showed that 50% bottom ash and 12% lime had developed some density and cementation after curing for longest time period.