Laboratory Study on the Impact of Ferrochrome Slag and Zycobond for Stabilization of Marine Clay Subgrade

Abstract

India, with a coastline stretching over 7,516 kilometers, relies heavily on its coastal infrastructure to support import and export activities that are vital to the nation\'s economic growth.The subsoil in many of these regions predominantly consists of marine clay, which is highly compressible, weak in shear strength, and highly susceptible to moisture variations making it unsuitable for pavement subgrades.These unfavourable characteristics compromise the stability and load-bearing capacity of foundations and infrastructure built on such soils.This study investigates the effectiveness of ferrochrome slag, an industrial by-product, and Zycobond, a chemical soil stabilizer, in enhancing the properties of marine clay.Experimental results reveal that the addition of FCS and Zycobond significantly enhances the strength and stability of the clay.The optimum blend resulted in a substantial increase in CBR value, making the treated marine clay suitable for pavement subgrade layers.The study concludes that the combined use of ferrochrome slag and Zycobond provides a cost-effective and sustainable solution for stabilizing weak soils.

Introduction

India’s vast coastline supports significant industrial and infrastructural development, but the presence of weak and compressible marine clays poses a major challenge. These soils have low bearing capacity, high plasticity, and high compressibility, making them unsuitable for direct construction of heavy structures like ports, roads, and buildings. Without stabilization, structures built on such soils may suffer settlement and failure.
Therefore, soil stabilization is necessary to enhance strength, reduce compressibility, and improve durability—especially for use as pavement subgrade material.

Objectives of the Study

1. Evaluate geotechnical properties of untreated marine clay.

2. Examine the effect of ferrochrome slag (FCS) as a stabilizing additive.

3. Assess the role of Zycobond, a polymer-based binder, in combination with FCS.

4. Determine the suitability of the treated clay for pavement subgrade applications.

Materials Used

• Marine Clay: Collected from Kakinada Seaport, Andhra Pradesh; classified as high plastic clay (CH) with low strength and high swell potential.

• Ferrochrome Slag (FCS): A steel industry by-product containing oxides of Si, Al, Mg, Ca, and Cr, used to improve soil strength.

• Zycobond: A chemical stabilizer with polymer and ammonium compounds that improve soil bonding and reduce plasticity.

Methodology

Laboratory tests (Atterberg Limits, Free Swell, Compaction, CBR, and Triaxial Tests) were conducted on marine clay treated with varying percentages of FCS and Zycobond to evaluate improvements in strength and stability.

Results and Discussion

• Ferrochrome Slag Alone:
  Optimum FCS content = 16% → improved CBR from 1.58% to 5.24%, still below the IRC 37-2012 requirement of 8% for pavement subgrade.
  → Hence, FCS alone insufficient.

• Ferrochrome Slag + Zycobond:
  With 16% FCS + 2.5% Zycobond, CBR increased to 9.46%, meeting IRC standards.
  → Also reduced liquid limit, plasticity, and swell; increased dry density and shear strength.

Conclusion

The following results were derived by stabilizing the marine clay using Ferrochrome slag and Zycobond. 1) It is observed from the laboratory test results that the Liquid limit of Marine Clay has been decreased by 18.16% on the addition of 16% FCS and it has been further decreased by 36.02% with an addition of 2.5% Zycobond. 2) It is observed from the laboratory test results that the Plastic limit has been increased by 8.84% on addition of 16% FCS and it has been further increased by 18.86% with an addition of 2.5% Zycobond. 3) It is noticed that the Plasticity Index has been decreased by 36.75% on addition of 16% FCS and it has been further decreased by 73.63% with addition of 2.5% Zycobond. 4) It is noticed from the laboratory test results that the Differential Free Swell of Marine Clay has been reduced by 35.29% on the addition of 16% FCS and it has been further reduced by 82.35% with an addition of 2.5% Zycobond when compared with untreated Marine Clay. 5) It is observed from the laboratory tests that the OMC of the Marine Clay has been decreased by 23.85% on the addition of 16% FCS and it has been further decreased by 37.54% with addition of 2.5% Zycobond. 6) It is observed from the laboratory tests that the MDD of the Marine Clay has been increased by 26.58% on the addition of 16% FCS and it has been further increased by 33.98% with addition of 2.5% Zycobond. 7) It is observed that the CBR of the Marine Clay has been increased by 230.99% on the addition of 16% FCS and it has been further increased by 496.96% with addition of 2.5% Zycobond.

References

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Copyright

Copyright © 2025 Dr. D. Koteswwara Rao, J. Tejaswi. 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.