THESIS ABSTRACT

Abstract

Weak soil has excessive expansion & shrinkage characterstics. Due to these properties, the California Bearing Ratio & other properties are poor resulting to the changes in alignments or diffficult treatments for the construction of pavement. So, for the better solution, in this study, CBR improvement of Weak Subgrade Soil modified with the combination of fly ash, waste concrete fines and road dust and again with road dust only was carried out. For this, to identify the optimal percentage of RD for weak soil in terms of CBR, a varying percentage of RD (10%,15%,20%,25%) was mixed with the soil. Similarly, the percentage change of CBR value of the weak soil with other different combinations is also determined. At first, it’s modified with a mixture of constant percentage (15%) of fly ash& varying percentage (5%, 10%, 15%, 20%) of waste concrete fines and an optimum CBR value is obtained.The CBR value of optimum percentage obtained (weak soil+ 15%FA+ 15% WCF) is now again mixed with varying percentage of RD(5%, 7%, 10%,15%, 20%). From this result, WS+ optFAWCF+ 10% RD had the highest CBR value i.e 8.93. Here, the CBR value is increased by 206%.Among 16 different combination, 9 of them meet the CBR requirements per SSRBW 2016. The pavement thickness after adding RD only was 870mm which was greater compared to the other combinations. This combination is found to be the most economic as the cost per unit area is least in comparison to the other combinations. In terms of CBR & cost both, the addition of Road Dust is the suitable alternative.

Keywords

Weak Subgrade Soil, California Bearing Ratio, Fly Ash, Waste Concrete Fines, Road Dust