Determination of Strength Parameters and Economic Analysis of Pavement Design by Treating Clay Soil with Fly Ash at Optimization Level

This experimental study investigates the improvement in strength and economic performance of clayey subgrade soil stabilised with varying percentages of fly ash. A 6.735 km flexible pavement stretch from Hastinapur to Makhdoompur, District Meerut (U.P.), was considered for design analysis. Laboratory tests, including specific gravity, Atterberg limits, sieve analysis, hydrometer analysis, standard Proctor compaction, and California Bearing Ratio (CBR) tests, were performed. Results indicated that the addition of fly ash significantly improved the engineering properties of the clay soil. The CBR value increased from 5.88 to 18.78, leading to an approximate 20% reduction in pavement thickness and construction cost. The study concludes that 22.5% fly ash addition is the optimal level for achieving desirable strength and cost-efficiency in pavement subgrade stabilisation.