Mechanical and Microstructural Behaviour of Expansive Soil Stabilised with Granite Waste Powder

Abstract

Expansive soils exhibit significant volume change behaviour due to moisture variation, leading to serious stability and durability issues in geotechnical and pavement structures. This study evaluates the mechanical and microstructural behaviour of expansive soil stabilized with granite waste powder (GWP), an industrial by-product generated during granite processing. Soil samples were treated with varying GWP contents (0%, 5%, 10%, 15%, and 20%) and tested for index properties, compaction characteristics, strength parameters, and swelling behaviour. Results indicated a substantial reduction in liquid limit (62% to 47%) and plasticity index (34% to 15%), signifying decreased soil plasticity. The maximum dry density increased from 16.2 to 18.0 kN/m³, while optimum moisture content decreased with increasing GWP content. Strength behaviour showed significant improvement, with unconfined compressive strength increasing from 185 kPa to 410 kPa and soaked CBR from 3.8% to 10.8% at 15% GWP. Swell potential and swell pressure were markedly reduced, confirming the effectiveness of stabilization. Microstructural analyses using SEM, XRD, and EDS revealed a denser soil matrix, improved particle bonding, and mineralogical alterations due to physico-chemical interaction and filler effects. The study concludes that granite waste powder is an effective, sustainable, and economical stabilizing agent for expansive soils, particularly suitable for subgrade and pavement applications.

Introduction

Expansive soils, prone to swelling and shrinkage under moisture changes, cause structural issues such as cracking, differential settlement, and reduced bearing capacity, making stabilization essential. Traditional methods like lime and cement are effective but costly and environmentally taxing, prompting exploration of sustainable alternatives. Industrial by-products, particularly granite waste powder (GWP), have emerged as a promising stabilizer due to their filler properties, reactive silica content, and ability to improve soil strength, stiffness, and reduce plasticity and swell potential.

This study evaluates the mechanical and microstructural behavior of expansive soil stabilized with varying percentages of GWP (0–20%). Key findings include:

• Index properties: Liquid limit and plasticity index decreased, shifting soil from highly plastic (CH) to low plastic clay (CL).

• Compaction: Maximum dry density increased while optimum moisture content decreased, improving packing and reducing water affinity.

• Strength: Unconfined Compressive Strength (UCS) and California Bearing Ratio (CBR) improved significantly, peaking at 15% GWP.

• Swelling: Free swell index and swell pressure were drastically reduced, indicating improved dimensional stability.

• Microstructural analysis (SEM, XRD, EDS): GWP addition created a denser soil matrix, reduced clay mineral peaks, increased quartz and calcium content, and promoted physico-chemical bonding.

The stabilization mechanism combines mechanical packing, filler effects, and mild pozzolanic reactions, leading to enhanced cohesion, reduced compressibility, and better geotechnical performance. Overall, GWP offers a cost-effective, environmentally friendly solution for improving expansive soils in pavements and subgrade applications, with an optimum stabilization effect observed around 15–20% GWP content.

Conclusion

The present study investigated the mechanical and microstructural behaviour of expansive soil stabilized with varying percentages of granite waste powder (GWP). The results demonstrated that the inclusion of GWP effectively modified the index properties by reducing liquid limit and plasticity index, thereby decreasing the soil’s expansive nature. Compaction characteristics improved with an increase in maximum dry density and a corresponding reduction in optimum moisture content up to an optimum GWP content of about 15%. Significant enhancement in strength behaviour was observed, with notable increases in unconfined compressive strength and soaked CBR values, indicating improved load-bearing capacity suitable for pavement subgrade applications. Additionally, swell potential and swell pressure were considerably reduced, confirming the effectiveness of GWP in mitigating the adverse volume change behaviour of expansive soils. Microstructural analyses through SEM, XRD, and EDS revealed densification of the soil matrix, improved particle bonding, and mineralogical modifications due to the presence of silica-rich granite fines. These findings established a strong correlation between microstructural transformation and macroscopic strength improvement. Overall, granite waste powder proved to be an efficient, sustainable, and cost-effective stabilizing agent for expansive soils, with optimum performance observed around 10–15% replacement. The study confirms that the reuse of industrial granite waste not only enhances soil engineering properties but also contributes to environmentally sustainable ground improvement practices in geotechnical and pavement engineering applications.

References

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Copyright

Copyright © 2026 Mr. Ajit Barik, Mr. Amiyajyoti Nayak, Ms. Aditi Patnaik, Ms. Indira Priyadarshini Padhy. 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.