Stabilization of weak subgrade soil using lime and fly ash: A case study from Afghanistan

By improving poor subgrade soil using stabilizing methods and evaluating the effects of high moisture content, the research aims to lower building costs by improving engineering qualities with cementitious additives. Samples of disturbed soil were gathered from Mahle-Nijat, Kandahar, and examined at Kandahar University's civil laboratory. Specific gravity, Atterberg limits, and grain size distribution were among the index characteristics that were identified. As stabilizers, lime and fly ash were chosen and added in different amounts; fly ash ranged from 4 to 16 % by dry weight, while lime ranged from 4 to 10 %. The samples were compressed using the Modified Proctor Test to determine their Maximum Dry Density (MDD) and Optimum Moisture Content (OMC), and then the California Bearing Ratio (CBR) was measured. After 96 h, measurements of the soaked CBR were made. With CBR values rising from 3.6 for raw soil to 36.2 for the combination of 6 % lime and 8 % fly ash, the results showed significant improvements. Lime performed best at 6 %, while fly ash performed best between 4 and 12 %. In comparison to untreated samples, stabilized soils showed decreased flexibility and increased strength. In pavement construction, the combined lime-fly ash treatment significantly improved CBR values, demonstrating that this approach is both practical and cost-effective for increasing the load-bearing capacity of subgrade soils. • Lime and fly ash improve engineering properties of weak subgrade soil. • Fly ash and lime reduce soil plasticity and increase durability. • California Bearing Ratio values rises significantly with lime-fly ash treatment. • Optimal mix of lime and fly ash enhances soil performance effectively. • Method is cost effective and sustainable for pavement design.