AN INVESTIGATIVE STUDY ON EFFECT OF TERRAZYMES ON BLACK COTTON SOILS

Abstract

Soil stabilization using microbial bio-enzymes has emerged as a sustainable and cost-effective technique to enhance the engineering properties of problematic soils, particularly expansive clays. These organic catalysts, derived from microbial fermentation, interact with soil particles to alter their physicochemical characteristics, improve load-bearing capacity, and mitigate volumetric changes associated with moisture variations. This abstract presents an overview of the influence of microbial bio-enzymes on various critical soil parameters, including pH conditions, swelling behavior, unconfined compressive strength (UCS), California Bearing Ratio (CBR), and microstructural properties. PH conditions within the treated soil significantly influence the effectiveness of TerraZymes. Bio-enzymes typically exhibit optimal activity in slightly acidic to neutral pH environments (approximately 6.0 to 7.5). Soils with extremely high or low pH may inhibit enzymatic function or alter the reaction mechanism with clay minerals. Post-treatment, a stabilization of pH levels is commonly observed, indicating a reduction in ion exchange activity and a more stable electrochemical environment conducive to particle flocculation and reduced plasticity. One of the major challenges in geotechnical engineering is the swelling behavior of expansive soils, primarily due to the presence of montmorillonite and other active clay minerals. Bio-enzyme treatment significantly mitigates this issue by disrupting the diffuse double layer surrounding clay particles. This process reduces water affinity and shrink-swell potential. Laboratory tests such as free swell index and swell pressure indicate a marked decrease in swelling potential, often by 40–60% compared to untreated soils. This behavior translates into improved dimensional stability of road subgrades and embankments under cyclic wetting and drying conditions. The Unconfined Compressive Strength (UCS) of soil, a key indicator of its structural integrity, is substantially improved upon enzyme application. The bio-enzymes facilitate closer packing of soil particles, enhanced inter-particle bonding, and densification, leading to UCS increases of 1.5 to 3 times within 7 to 28 days of curing. These improvements make enzyme-treated soils suitable for low to medium traffic load-bearing applications, reducing reliance on conventional chemical stabilizers such as cement or lime. Similarly, California Bearing Ratio (CBR) values demonstrate significant enhancement post bio-enzyme treatment. Field and laboratory CBR values have shown increases ranging from 50% to over 200%, depending on soil type, compaction effort, and curing period. This directly contributes to reduced pavement thickness requirements and increased durability of unpaved roads in rural and semi-urban areas. Microstructural analysis through Scanning Electron Microscopy (SEM) reveals a distinct transformation in soil fabric. Enzyme-treated soil displayed denser, aggregated structures with fewer voids and a reduction in crystalline clay mineral peaks. The TerraZymes offer a promising result for sustainable soil stabilization by improving critical geotechnical parameters. Their influence on pH balance, swelling reduction, strength enhancement, and microstructural densification makes them a viable alternative to traditional methods, especially in regions prioritizing environmental conservation and cost-effective infrastructure development.