The development of alternatives to soil stabilization through mechanical and chemical stabilization has paved the way for the development of biostabilization methods. Since its development, researchers have used different bacteria species for soil treatment. Soil treatment through bioremediation techniques has been used to understand its effect on strength parameters and contaminant remediation. Using a living organism for binding the soil grains to make the soil mass dense and durable is the basic idea of soil biotreatment. Bacteria and enzymes are commonly utilized in biostabilization, which is a common method to encourage ureolysis, leading to calcite precipitation in the soil mass. Microbial-induced calcite precipitation (MICP) and enzyme-induced calcite precipitation (EICP) techniques are emerging trends in soil stabilization. Unlike conventional methods, these techniques are environmentally friendly and sustainable. This review determines the challenges, applicability, advantages, and disadvantages of MICP and EICP in soil treatment and their role in the improvement of the geotechnical and geoenvironmental properties of soil. It further elaborates on their probable mechanism in improving the soil properties in the natural and lab environments. Moreover, it looks into the effectiveness of biostabilization as a remediation of soil contamination. This review intends to present a hands-on adoptable treatment method for in situ implementation depending on specific site conditions.

https://www.mdpi.com/2073-4352/11/4/370/pdf

State-of-the-Art Review of the Applicability and Challenges of Microbial-Induced Calcite Precipitation (MICP) and Enzyme-Induced Calcite Precipitation (EICP) Techniques for Geotechnical and Geoenvironmental Applications

This study intended to address the problem of damaged (collapsed, cracked and decreased soil strength) road pavement structure built on clay soil due to clay soil properties such as low shear strength, high soil compressibility, low soil permeability, low soil strength, and high soil plasticity. Previous research reported that ground granulated blast slag (GGBS) and fly ash can be used for clay soil stabilizations, but the results of past research indicate that the road pavement construction standards remained unfulfilled, especially in terms of clay’s subgrade soil. Due to this reason, this study is carried out to further investigate soil stabilization using GGBS and fly ash-based geopolymer processes. This study investigates the effects of GGBS and ratios of fly ash (solid) to alkaline activator (liquid) of 1:1, 1.5:1, 2:1, 2.5:1, and 3:1, cured for 1 and 7 days. The molarity of sodium hydroxide (NaOH) and the ratio of sodium silicate (Na2SiO3) to sodium hydroxide (NaOH) was fixed at 10 molar and 2.0 weight ratio. The mechanical properties of the soil stabilization based geopolymer process were tested using an unconfined compression test, while the characterization of soil stabilization was investigated using the plastic limit test, liquid limit test, scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The results showed that the highest strength obtained was 3.15 MPA with a GGBS to alkaline activator ratio of 1.5 and Na2SiO3 to NaOH ratio of 2.0 at 7 days curing time. These findings are useful in enhancing knowledge in the field of soil stabilization-based geopolymer, especially for applications in pavement construction. In addition, it can be used as a reference for academicians, civil engineers, and geotechnical engineers.

Evaluation on the Mechanical Properties of Ground Granulated Blast Slag (GGBS) and Fly Ash Stabilized Soil via Geopolymer Process

Optimization of fly ash based soil stabilization using secondary admixtures for sustainable road construction

Geopolymers, or also known as alkali-activated binders, have recently emerged as a viable alternative to conventional binders (cement) for soil stabilization. Geopolymers employ alkaline activation of industrial waste to create cementitious products inside treated soils, increasing the clayey soils’ mechanical and physical qualities. This paper aims to review the utilization of fly ash and ground granulated blast furnace slag (GGBFS)-based geopolymers for soil stabilization by enhancing strength. Previous research only used one type of precursor: fly ash or GGBFS, but the strength value obtained did not meet the ASTM D 4609 (<0.8 Mpa) standard required for soil-stabilizing criteria of road construction applications. This current research focused on the combination of two types of precursors, which are fly ash and GGBFS. The findings of an unconfined compressive strength (UCS) test on stabilized soil samples were discussed. Finally, the paper concludes that GGBFS and fly-ash-based geo-polymers for soil stabilization techniques can be successfully used as a binder for soil stabilization. However, additional research is required to meet the requirement of ASTM D 4609 standard in road construction applications, particularly in subgrade layers.

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Potential of Soil Stabilization Using Ground Granulated Blast Furnace Slag (GGBFS) and Fly Ash via Geopolymerization Method: A Review

This study explores the possibility of using sustainable materials in the form of fly ash as a precursor in alkali activation (AA) reactions, as well as coir fibres as discrete reinforcement. For e...

Improving the engineering behaviour of residual soil with fly ash and treated natural fibres in alkaline condition

Development and use of non-traditional stabilizers such as enzyme and alkali-activated ground granulated blast-furnace slag (GGBS) for soil stabilization helps to reduce the cost and the detrimental effects on the environment. The objective of this study is to investigate the effectiveness of alkali-activated GGBS and enzyme as compared to ordinary Portland cement (OPC) on the soil collected from Tilda region of Chhattisgarh, India. Geopolymers are alkali alumino-silicates produced when combining a solid alumina-silicate with an aqueous alkali hydroxide or silicate solution. Various dosages of the selected stabilizers have been used and evaluated for the effects on optimum moisture content (OMC), maximum dry density, plasticity index, unconfined compressive strength (UCS) and shear strength parameters. Effect of curing period has also been studied. Microstructural changes of the stabilized soils show aggregation of particles. Significant improvement in properties of soil is observed with the addition of stabilizers leading to an increase in OMC, UCS and shear strength parameters. It is observed that the cohesion of soil sample increases significantly with the addition of stabilizers whereas there is a marginal change in angle of internal friction. Thus, the findings recommend the use of non-conventional stabilizer such as alkali-activated GGBS and enzyme as suitable and environmental friendly as compared to OPC for soil stabilization.

A Laboratory Investigation of Soil Stabilization Using Enzyme and Alkali-Activated Ground Granulated Blast-Furnace Slag

Variation in a Shear Modulus of Enzyme-Treated Soil under Cyclic Loading

In this study, the effect of dosage of enzyme (50 to 400 ml/m3), curing period (7 to 28 days) and cyclic triaxial loading test parameters such as confining pressure (50 to 200 kPa), loading frequency (0.25 to 1 Hz) and loading rate (0.3 to 0.9%) on the shear modulus of enzyme stabilized soil is investigated. Taguchi method has been applied to the cyclic triaxial tests, and L16 orthogonal array with five factors and four levels was selected. Analysis of variance was carried out to study the significant factors affecting the response. Among the selected factors considered for the study, curing period is found to be the most effective parameter on the shear modulus of the enzyme treated soil. With the increase in dosage of the stabilizer, there is a significant improvement in the shear modulus of the treated soil. The increase in shear strain amplitude and loading frequency decreases the shear modulus. The higher value of shear modulus was obtained for the specimen with dosage of enzyme 400 ml/m3 after a curing period of 28 days under a confining pressure of 200 kPa, loading frequency of 0.25 Hz and cyclic shear strain amplitude of 0.3%.

Ansu Thomas

Papers

A Laboratory Investigation of Soil Stabilization Using Enzyme and Alkali-Activated Ground Granulated Blast-Furnace Slag

Variation in a Shear Modulus of Enzyme-Treated Soil under Cyclic Loading

Application of Taguchi Method for Optimization of Various Factors in Improving the Shear Modulus of Enzyme Treated Soil