Investigation of the effectiveness and mechanisms of enzyme products for subgrade stabilization

Abstract

The subgrade stabilization effectiveness and mechanisms of two enzyme products (enzyme A and B) were investigated using chemical analysis and resilient modulus testing. Two types of soil were tested in this study. A soil with a high percentage of fines (96.4% passing 200 sieve) and high clay content (75.2%) (Soil I) and a soil with a relatively low fines content (59.7% passing 200 sieve) and low clay content (14.5%) (Soil II). The addition of enzyme A did not improve significantly the resilient modulus of Soil I, but increased the resilient modulus of Soil II by an average of 54%. On the other hand, the addition of enzyme B significantly increased the resilient modulus of both soils. The soil clay content and percent of fines appear to play an important role in the effectiveness of enzyme-based stabilizer treatment. The limited effectiveness of enzyme A (for low clay content soil) appears to be due to its surfactant-like characteristics while enzyme B, which was effective for both soils, exhibited no surfactant-like characteristics.

Keywords:

• Enzyme stabilization
• Resilient modulus
• Surface tension
• pH
• Metals concentrations
• Protein content and enzymatic activity

Acknowledgements

The financial support provided by Minnesota Local Road Research Board (LRRB) and the Minnesota Department of Transportation is gratefully acknowledged. The help provided in the chemical analysis and mechanical testing by Li Zhang and Timothy R. Clyne is acknowledged.