Performance Evaluation of Soil Stabilization Using Lime & Fly Ash

Abstract

The improvement of weak subgrade soils remains a critical challenge in geotechnical engineering, particularly for infrastructure development in developing regions. This study presents a detailed experimental investigation on the stabilization of soil using lime and fly ash as chemical additives. Soil samples were treated with varying percentages (0%, 5%, 10%, 15%, and 20%) of stabilizers and tested for key engineering properties including California Bearing Ratio (CBR), Maximum Dry Density (MDD), and Atterberg limits. The results reveal that both stabilizers significantly enhance soil strength due to pozzolanic reactions and physicochemical modifications. The maximum improvement in CBR was observed at 15% stabilizer content, with lime exhibiting slightly superior performance (12.57%) compared to fly ash (10.71%). However, fly ash demonstrates better sustainability potential due to its industrial waste origin. The study concludes that optimum stabilization improves subgrade performance while reducing environmental impact and construction costs.

Introduction

The study focuses on improving weak and expansive soils that are unsuitable for construction by using chemical stabilization techniques. Poor soil conditions can cause problems such as excessive settlement, low bearing capacity, and volume changes, affecting the safety and durability of structures, roads, and bridges. Lime and fly ash are selected as stabilizers due to their availability, cost-effectiveness, and ability to improve soil properties through chemical reactions.

Lime improves soil strength by reducing plasticity and promoting cation exchange, flocculation, and pozzolanic reactions, while fly ash reacts with calcium and water to form cementitious compounds that enhance soil stability. The research aims to compare the performance of lime and fly ash in improving soil strength, particularly for pavement and construction applications.

The study reviews previous research showing that lime–fly ash mixtures can increase California Bearing Ratio (CBR), reduce plasticity, and improve durability. However, determining the optimum stabilizer percentage for different soil types remains a key challenge.

In the experimental methodology, soil samples were collected from the Oriental Institute of Science and Technology, Bhopal. The soil was mixed with varying percentages (5%, 10%, 15%, 20%, and 25%) of fly ash and lime. Laboratory tests including sieve analysis, specific gravity, liquid limit, plastic limit, Standard Proctor test, and CBR test were conducted to evaluate changes in soil properties.

The results showed that stabilization significantly improved soil strength. The CBR value increased from 0.89% for untreated soil to a maximum of 10.71% with 15% fly ash and 12.57% with 15% lime, indicating improved load-bearing capacity. Liquid limit values initially decreased with stabilizer addition but increased after higher percentages. Maximum dry density (MDD) decreased up to 10–15% stabilizer content and slightly increased afterward.

Conclusion

The following conclusions can be drawn from the experimental work on soil stabilisation with fly ash and lime: Specific gravity was shown to drop up to 15% as the proportion of fly ash in soil increased, but it slightly increased after that. A similar pattern was observed with lime addition. The effect of fly ash on soil liquid limit was unusual, with addition up to 5% resulting in a fall in liquid limit and a progressive increase on additional addition up to 20%, which was even bigger than the original liquid limit of the soil utilised. The same was true with lime. The soil plastic limit was 25%, and it gradually decreased with the addition of fly ash and lime up to 10%, after which it marginally increased. OMC decreased by 2% with the addition of fly ash and by 3% with the addition of lime. Soil MDD was 2.01g/cm3, which dropped to 1.92g/cm3 after 10% fly ash addition and increased slightly to 1.95g/cm3 with additional addition. In the case of lime, the MDD decreased but not as much as in the case of fly ash, with a minimal decrease of 1.94g/cm3 followed by a tiny increase to 1.97g/cm3. CBR @ 2.5mm for soil was 0.49, increasing to 4.16 with 10% fly ash addition, then a massive rise to 10.71 with 15% addition, although it dropped with additional addition. In the case of lime, there was a linear increase up to 10%, but at 15%, the value increased even more than in the case of fly ash, to 12.57. As a result, soil with an optimal amount of fly ash and lime (15-20%) is most suited and cost-effective for highway construction.

References

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Copyright

Copyright © 2026 Avi Rana, Kamal Singh Rathour, Rohit Toppo, Sachin Prajapati, Shekhar Pancheshwar, Shivani Singh Baghel. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.