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<p>Expansive soils, characterized by high plasticity, inherently low strength, and pronounced shrink–swell behavior, pose significant challenges during construction and must be carefully managed to ensure structural integrity and long-term durability. Conventional stabilizers, such as cement and lime, are widely used to improve various soil properties; however, these traditional methods are often associated with high energy consumption and significant environmental impacts, raising concerns about their sustainability. In this study, an attempt is made to explore the efficacy of expansive soil that has been stabilized through the application of fly ash, calcium carbide residue (CCR), and TerraZyme. TerraZyme is an environmentally friendly enzymatic stabilizer that has garnered attention for its potential eco-sustainability. The primary focus of this research is to evaluate the performance of the stabilized soil. To achieve this, a series of laboratory experiments were systematically conducted to assess the impacts of these stabilizers on various soil characteristics, including the Atterberg limits, unconfined compressive strength (UCS), California bearing ratio (CBR), and overall durability when subjected to repeated wetting–drying cycles. The results of the experiments related to UCS and CBR demonstrated significant improvements in soil strength, particularly at the optimal dosages of fly ash (6%), calcium carbide residue (8%), and TerraZyme (0.6%). At these optimum dosages, the 28‑day unconfined compressive strength (UCS) rose from 217.3&#xa0;kPa for the natural soil to 3255.87&#xa0;kPa, approximately a 15-fold gain, and the soaked California bearing ratio (CBR) increased from 2.4 to 34.2% (approximately 14‑fold improvement). Mass loss after 12 wetting–drying cycles fell from 22 to 6.7%, while residual UCS loss halved from 44 to 22%, confirming long‑term durability. Compared to conventional binder stabilization, the enzyme–industrial waste system offers higher strength and bearing capacity while simultaneously valorizing waste materials and avoiding the use of high-carbon binders. The synergy between pozzolanic reactions (fly ash–CCR) and TerraZyme‑induced clay flocculation produces a dense, moisture‑resistant matrix. The results indicate that the FA6CCR8T0.6 blend is a viable and sustainable alternative to conventional cement- or lime-based treatments for foundations and pavement subgrades in expansive soils.</p>

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Performance Evaluation of Expansive Soil Stabilized with Fly Ash, Calcium Carbide Residue, and TerraZyme

  • 期刊论文

  • 发表日期：

    2025年7月31日

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  • Alamuru Baba Sankar,
  • D. Viswanath,
  • Yeswanth Paluri

摘要

Expansive soils, characterized by high plasticity, inherently low strength, and pronounced shrink–swell behavior, pose significant challenges during construction and must be carefully managed to ensure structural integrity and long-term durability. Conventional stabilizers, such as cement and lime, are widely used to improve various soil properties; however, these traditional methods are often associated with high energy consumption and significant environmental impacts, raising concerns about their sustainability. In this study, an attempt is made to explore the efficacy of expansive soil that has been stabilized through the application of fly ash, calcium carbide residue (CCR), and TerraZyme. TerraZyme is an environmentally friendly enzymatic stabilizer that has garnered attention for its potential eco-sustainability. The primary focus of this research is to evaluate the performance of the stabilized soil. To achieve this, a series of laboratory experiments were systematically conducted to assess the impacts of these stabilizers on various soil characteristics, including the Atterberg limits, unconfined compressive strength (UCS), California bearing ratio (CBR), and overall durability when subjected to repeated wetting–drying cycles. The results of the experiments related to UCS and CBR demonstrated significant improvements in soil strength, particularly at the optimal dosages of fly ash (6%), calcium carbide residue (8%), and TerraZyme (0.6%). At these optimum dosages, the 28‑day unconfined compressive strength (UCS) rose from 217.3 kPa for the natural soil to 3255.87 kPa, approximately a 15-fold gain, and the soaked California bearing ratio (CBR) increased from 2.4 to 34.2% (approximately 14‑fold improvement). Mass loss after 12 wetting–drying cycles fell from 22 to 6.7%, while residual UCS loss halved from 44 to 22%, confirming long‑term durability. Compared to conventional binder stabilization, the enzyme–industrial waste system offers higher strength and bearing capacity while simultaneously valorizing waste materials and avoiding the use of high-carbon binders. The synergy between pozzolanic reactions (fly ash–CCR) and TerraZyme‑induced clay flocculation produces a dense, moisture‑resistant matrix. The results indicate that the FA6CCR8T0.6 blend is a viable and sustainable alternative to conventional cement- or lime-based treatments for foundations and pavement subgrades in expansive soils.