Performance Assessment of Fly Ash and Cement in Stabilizing Low Strength Soil
DOI:
https://doi.org/10.64862/Keywords:
Stabilization, Additives, Soil modification, Direct shear testAbstract
The increasing rate of infrastructure development highlights the importance of geotechnical engineering in achieving sustainable and resilient construction. In many regions, particularly in Bangladesh, weak or expansive soils pose significant challenges, leading to structural failures in roads, pavements, embankments, and other critical facilities. This study investigates the potential of fly ash (F.A.) and cement as stabilizing agents to improve the engineering properties of low-strength clayey-silt soils. Laboratory tests were conducted on soil samples mixed with varying proportions of F.A. (5%, 10%, 15%, and 20%) and the same F.A. contents combined with 2% cement. The test results revealed that specific gravity decreased with increasing F.A. content due to its low unit weight but increased slightly compared to corresponding F.A.-only mixtures when cement was added, owing to cement’s higher density. The liquid limit, plasticity index, and linear shrinkage decreased progressively with F.A. addition and were further reduced by cement incorporation, while the plastic limit increased, indicating improved workability and a change in soil type from clayey to silty. Direct shear tests showed that cohesion increased with F.A. content up to 15% before declining, whereas the friction angle increased steadily. The highest cohesion (36.36 kPa) was achieved with 15% F.A. + 2% cement, and the maximum friction angle (34.49°) occurred at 20% F.A. + 2% cement. Reactive oxides were found in fly ash and cement, according to XRF analysis, which supported the pozzolanic reactions. These results demonstrate that the combined use of F.A. and cement significantly enhances shear strength and reduces shrinkage, offering a cost-effective and environmentally sustainable solution for stabilizing weak soils. The findings align with the Sustainable Development Goals by promoting resilient infrastructure and safer construction practices in challenging geotechnical environments.
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