Stabilization of Soil Using Sodium Alginate Biopolymer

Abstract

Soil stabilization refers to a variety of strategies and tactics used to strengthen a soil of problematic geotechnical characteristics and increase its capacity to support loads. Although several materials, including as bitumen, cement, and lime, are used to improve the qualities, they are not environmentally friendly. This study aims to investigate how sodium alginate, a naturally occurring polymer, can enhance the mechanical characteristics of alluvial soil. Compared to other traditional materials, this biopolymer has a lower carbon impact and is naturally biodegradable. To identify the optimum dosage needed for stabilization, four different variable proportions of sodium alginate with soil—0.5%, 1.0%, 2.0%, and 3.0%were utilized. Three key characteristics, such as the relationship between the optimal moisture content and maximum dry density relation, California Bearing Ratio Test (both unsoaked and soaked) and Unconfined Compressive Strength Test were studied on the soil and mixes. From the results it was concluded that soil with 3.0% Sodium alginate has shown maximum improvement in the geotechnical properties of soil.

Introduction

Here's a summary of the provided text on the use of sodium alginate (SA) in soil stabilization:

Summary:

1. Introduction:
Ground improvement is crucial for supporting infrastructure on weak or unstable soils. Traditional methods (e.g., cement, lime) are effective but environmentally damaging. In response, eco-friendly biopolymers like sodium alginate, derived from seaweed and abundantly available in India, are being explored due to their non-toxic, biodegradable nature and effective soil-binding properties.

2. Need and Scope of the Study:

• Need: India’s expanding infrastructure requires sustainable soil stabilization. Traditional materials increase carbon emissions.

• Scope: This study evaluates sodium alginate as a green alternative to conventional stabilizers by testing its effects on soil strength, cohesion, and durability. The goal is to determine the optimum dosage and assess its environmental and economic viability.

3. Objectives:

• Determine Atterberg limits and classify the soil.

• Measure OMC, MDD, UCS, CBR, and permeability for both untreated and SA-treated soils.

• Identify the optimal SA content (0.5%, 1%, 2%, 3%) for stabilization.

• Compare test results of treated vs. virgin soil.

4. Research Methodology:

• Initial characterization of soil: specific gravity, particle size, Atterberg limits.

• Conduct tests: Proctor compaction, UCS, CBR, Direct Shear.

• Mix sodium alginate with soil and repeat tests to assess performance.

• Compare results to identify the most effective SA dosage.

5. Experimental Description:

• Soil from Muzaffarpur, Bihar and sodium alginate from IndiaMart.

• Detailed procedures for compaction, UCS, CBR, and shear strength tests were carried out.

6. Results and Discussion:

Soil Properties:

• Specific Gravity: 2.70; Liquid Limit: 34%; Plastic Limit: 19%; MDD: 1.64 g/cm³; OMC: 17.8%.

Effect of Sodium Alginate:

• OMC decreases and MDD increases with higher SA content.

• At 3% SA: MDD = 1.81, OMC = 14.6%.

Atterberg Limits:

• LL and PL increase with SA content, indicating higher plasticity and better binding.

CBR Results:

• Soaked CBR improves from 2.5% (untreated) to 7.7% (3% SA).

• Unsoaked CBR increases from 6.1% to 20.5%, indicating enhanced load-bearing.

UCS Test:

• UCS improves from 192.6 kPa (untreated) to 540 kPa (3% SA), showing major strength gain.

Direct Shear Test:

• Cohesion (C) rises from 6.1 to 45.3 kPa.

• Friction angle (φ) improves slightly from 26.1° to 29.1° with SA.

Conclusion

1) The liquid limit of soil increases significantly with the addition of sodium alginate (SA). It was around 34% for pure soil, while at 3% SAC, it increased to 62%. 2) The plastic limit also increases with SAC, rising from 19% for untreated soil to 31% at 3% SAC. 3) Adding sodium alginate shifts the compaction curve leftward and upward. The maximum dry density increases from 1.64 g/cc for untreated clay to 1.81 g/cc at 3% SAC, while the optimum moisture content (OMC) decreases from 17.8% to 14.6%. 4) The California Bearing Ratio (CBR) improves steadily with increasing SAC under both soaked and unsoaked conditions. Under wet conditions, the highest CBR value is achieved at 3% SAC, indicating enhanced load-bearing capacity. Unsoaked soils exhibit even greater CBR values for the exact SAC percentages, highlighting the effectiveness of SA in improving soil strength, particularly in dry conditions. 5) Untreated soil has a UCS of approximately 192 kPa, while at 3% SAC, the UCS improves by 2.8 times, reaching the highest peak stress among all samples. 6) Sodium alginate increases the cohesion and angle of internal friction of soil, as observed from the failure envelopes in the direct shear test (DST). This improvement is attributed to the cementitious bonds formed by SA, which enhance resistance to particle movement during shearing.

References

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Copyright

Copyright © 2025 Sunny Raj, Er. Vinod Kumar Sonthwal. 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.