Anteneh Marilign (PhD)Bereket Mulugeta2024-03-122024-03-122023-11https://etd.aau.edu.et/handle/123456789/2467Huge machineries and lots of earthmovings are needed for soil stabilization procedure, which makes it an expensive and labor-intensive process. Finding novel, affordable materials that can advance construction methods and permit the growth of the road network is currently in high demand. Particularly, there has been a rise in interest in the hunt for novel, less expensive soil stabilizers and construction methods. At a height of about 2000 meters above mean sea level, Addis Ababa, the capital city of Ethiopia, is mostly covered in clay expansive soil. In engineering, it is crucial to enhance expansive soil; mechanical strength and swelling-shrinkage characteristics. In this study, an experimental investigation has been carried out to determine the possibility of stabilizing expansive black cotton soil (EBCS) using municipal sewage sludge ash (SSA). Prior to the experimental study compositional analysis of the EBCS and the SSA have been made using complete silicate analysis. The results revealed that the SSA can be used as Alternative supplementary cementitious materials (ASCM) and has more CaO content, which makes it suitable for Hydration and pozolanic reaction. Effect of adding variable composition of SSA, from 4 to 10%, in the EBCS performance characteristic has been analyzed. Parameters which were analyzed as performance indicators were stability conducted in the laboratory to obtain the California bearing ratio (CBR),Maximum Dry Density(MDD), and Atterberg limit (PI, LL, SL). Studying microstructural analysis of soil samples that passed through a 32μm sieve, the EBCS, SSA and soil-SSA composite were analyzed for surface area using a BET, and the results revealed a sizable reduction. Surface area for expansive soil is168.422 m2/gm and after SSA treatment, it was reduced to 145.646 m2/gm. Moreover, microstructural analysis using a scanning electron microscope (SEM) and complete silicate analysis was conducted to gain insight into the material behavior, and images from the SEM were analyzed through the Fiji Image J analyzer in order to characterize the surface texture characteristics of EBCS, SSA and soil-SSA composite. It is concluded from the present study that the SSA could be used for the stabilization of EBCS for highway subgrade. By reducing surface area and filling soil pores with sewage sludge ash, along with hydration reaction and some pozzolanic reaction between EBCS clay particle and SSA, it is possible to change the physical properties of soils to increase their capacity for bearing loads.en-USSewage sludge AshSoil stabilizationBlack Cotton Expansive SoilThesis