Effect of enzymes on plasticity and strength characteristics of an earthen construction material

Abstract

In this study, a commercially available enzyme which is used popularly to improve sub-grade material for pavements was used as a potential stabilizer to improve soil properties used for earthen construction. As a preliminary study, the interaction of this enzyme with the soil was assessed by evaluating the plasticity and strength characteristics of enzyme treated soil with ageing. From the research findings, it was observed that with ageing, the liquid limit of soil decreased, while plastic and shrinkage limits increased, leading to reduced plasticity and shrinkage indices. The reduced plasticity and shrinkage indices indicate that soil has become relatively more volumetrically stable and less susceptible to crack formation. Further, strength characteristics under two different curing conditions were evaluated, and it was found that under sealed curing conditions, the treated soil had better compressive strength. The improvement of plasticity, shrinkage and strength characteristics due to the addition of enzymes can be advantageously used for development of lightly stabilized durable earthen construction material, and thus, eliminating the necessity of using conventional energy-intensive stabilizers. The findings from this study bring the immense potential of eco-friendly enzymatic stabilization in the development of modern sustainable earthen materials.

Application of Microbial Bioenzymes in Soil Stabilization

“…Thus, there is relatively little literature concerning stabilization mechanisms of bioenzymes in soil stabilization. Two mechanisms of bioenzyme soil stabilization were proposed by researchers [ 44 ].…”

Strength and Volume Change Characteristics of Clayey Soils: Performance Evaluation of Enzymes

“…Soil strength improvement is one of the basic requirements of the construction field. Researchers have been making efforts to reduce the dependence on energy-intensive stabilizers such as cement and lime [1]. In this regard several non-traditional stabilizers have been tried for improving desirable soil characteristics, which include sulfonated oils, lignin derivatives, polymer-based additives, resins, enzymes, silicates, and calcium/sodium chloride geopolymers [2][3][4].…”

“…Further adding the doubts, enzymes are generally reformulation of other products therefore specific testing for a given enzyme is imperative [13]. Enzymes have actively supported in improving soil health [1,[14][15][16][17][18][19][20] A tropical red soil [1] and compressed stabilized earth blocks [17] were treated with TerraZyme and it was observed that the enzyme improved the compressive strength of the red soil and blocks. Soil (from Tilda region of Chhattisgarh, India) treated with enzyme showed considerable increase in cohesion though marginal increase in angle of internal friction was observed [21].…”

“…Soil (from Tilda region of Chhattisgarh, India) treated with enzyme showed considerable increase in cohesion though marginal increase in angle of internal friction was observed [21]. Treatment of enzyme (TerraZyme) with c clayey sand (SC, classified by Indian Standard) resulted in reduction of plasticity index and increase in unconfined compressive strength [1]. A clayey soil classified as CL, was treated with three enzymes but no improvement was observed [14].…”

“…Enzymes help to produce cementitious compounds by the following, general reaction. H2O + clay Enzyme → Calcium silicate hydrates (1) They treat adsorbed water with organic cations and neutralize the negative charge on the clay particles. The organic cations also trim down thickness of the electrical double layer.…”