Investigating Black Cotton Soil Blended with Basaltic Quarry Dust and Portland cement for Road Sub-grade Material (The Case of Akaki - Goro Road Segment)
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Date
2018-09
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Addis Ababa University
Abstract
The construction industry has presented different types of ground improvement techniques to modify and/or stabilize soils that exhibits expansive nature. Different chemical stabilizers have been used for stabilization of Black Cotton soils. Portland cement is the common one used for stabilizing black cotton soil. Though Cement is the effective soil stabilizing material, stabilizing soils with Cement alone would not be economically viable as Cement is relatively expansive. Hence, in this research work, investigation has been carried out to analyze the effect of blending Basaltic Quarry Dust and Portland cement on the properties of black cotton soil.
The performance of Cement and Quarry dust was evaluated based on laboratory tests on Black Cotton soil collected from Akaki-Goro road segment, Central part of Ethiopia, which was classified as A-7-6 or CL soil using AASHTO and USCS classifications respectively. The sample soil was treated with 0-12% Cement alone, 0-20% Quarry Dust alone and, with the combination of Cement and Quarry Dust mixture by keeping the 4%, 8% and 12% cement constant and varying the Quarry dust content by 5%, 10% 15% and 20% by dry weight of the soil.
The analysis of test results showed that, the sample soil treated with Cement alone shows significant improvement in strength parameters and lower the swelling potential of the treated soil. Whereas, for the soil treated with Quarry Dust alone, no significant improvements were observed on the strength and swelling potential of the treated soil; however reduction has been observed on the Plasticity Index of the quarry dust treated soil. On the other hand, for the soil stabilized with the combination of Quarry Dust and Cement mixture, very significant improvement in strength parameters and a substantial decrease in the plasticity index and swelling potential were recorded than the soil treated with Cement alone and the mixes of the two additives acts as a ‘Cement-Mortar’.
It has been concluded that, Quarry dust only by itself is not an effective stabilizer for stabilizing expansive soil. However, the combination of Cement and Quarry Dust mixture effectively stabilized the treated soil and the mix proportion of (4%OPC + 15%QD) is found to be the optimum stabilizer content for the studied soil to utilize it as a road subgrade soil.
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Keywords
Black Cotton Soil, Curing, Expansive Clay Soil, Portland-Cement, Quarry Dust, Soil Stabilization, Unconfined Compressive Strength