Understanding the behavior of expansive soil and adopting the appropriate control measures should be great for civil engineers. Extensive research has been going on to find the solutions associated with problems of expansive soils. There have been many methods available to control the expansiveness of these soils. The removal of expansive soils and replacement with suitable material has been widely practiced worldwide. Reasonable material is available within economic distances; however, suitable materials is not readily an available in urban areas for borrowing, which has to be hauled from a long distance. Instead of borrowing suitable soil from a long distance away, after stabilization with cost effective and readily available industrial and agricultural waste materials, it is economical to use locally available plastic soil. Such wastage products are also used to minimize environmental hazards such as CO2 in the atmosphere to minimize the percentage of industrial products used for stabilization, such as cement. Marble dust (MD), an industrial waste product, Rice husk ash (RHA), agricultural waste products, and cement are industrial products in this present study. The general objective of study was to examine the effects of poor subgrade soil stabilization using the mixture of MD, RHA and cement to enhance sub-standard soil engineering properties to be used as subgrade materials. Moisture content, Atterberg limits, grain size analysis, soil classification, free swell index, basic gravity, compaction (maximum dry density, optimum moisture content) and CBR value test have been calculated in this analysis. The design of the analysis followed by the experimental method of study were adopted, which started with sample selection. A disturbed samples was collected from the pit at a depth of 1.5 m to 2m from ground level in order to avoid the inclusion of organic matter by considering the free swell index value and observation was considered. The chemical analysis of MD and RHA was conducted in laboratory and the main oxides are (SiO2+Al2O3+Fe2O3) were 70.13% for RHA and 42.43% for MD. The RHA chemical properties satisfy the requirement, while MD did not meet the requirement of ASTM C 618. The Gomata Teachers’ Condominium (GTC) soil sample laboratory result have 42.72% plastic index (PI), 85% free swell index and its CBR value of 2.265%. The Millennium Secondary school (MSS) soil sample has a 48.79% PI, 87% free swell index and 2.121% CBR value. Therefore this soil samples are highly expansive were checked before any stabilizations process based on their plasticity index and CBR value based on standard specification requirement , then stabilization was achieved by stabilization by proposed (0,8MD,6MD+2C,4MD+4C,2MD+6C,8C,6MD+2RHA, 4MD+4RHA, 2MD+6RHA,8RHA,6RHA+2C,4RHA+4C,2RHA+6C,2MD+2RHA+4C,4MD+2RHA+2C, 2MD+4RHA+2C) proportion. Then LL, PI, OMC, and CBR decreased as the cement ratio increased, while PL, MDD and CBR value increases instead of MD and RHA increases, however, as MD and RHA increase, the quantity of cement decreases. The laboratory outcome was compared with the requirement of Ethiopian road authority standard, ASTM and AASHTO. Based on this study all mixing stabilizers (MD-cement, RHA-cement, MD-RHA, MD-RHA-cement) and 8% of RHA and cement fulfill the ERA standard specification requirements for its CBR swell value. However, 8% of marble dust alone does not fulfill the Ethiopia road authority requirements for CBR swell. The MD and RHA standalone does not improving some of the engineering properties of soil samples used for subgrade construction. However, they mixed with different percentages of cement can effectively stabilizer for this expansive soil for road sub-grade construction.
Engineering Properties of Bentonite Stabilized with Lime and Phosphogypsum
