Impact of freeze-thaw cycles on the dynamic CBR of unstabilized and enzyme-stabilized subgrade soil

Abstract

This study investigates the impact of freeze-thaw cycles on the dynamic California Bearing Ratio (CBR) of enzyme-stabilized and unstabilized subgrade soil. The research focuses on two enzyme-based stabilizers, Road Stabilizr and TerraZyme, applied to materials with varying plasticity indices. The results reveal that prior to conditioning, TerraZyme-stabilized samples exhibited an 11% increase in dynamic CBR, whereas Road Stabilizr-stabilized samples showed a slight decrease of 4% compared to unstabilized specimens. After subjecting the samples to freeze–thaw cycles, both enzyme-treated materials demonstrated substantially enhanced resistance to frost-induced degradation. Dynamic CBR increased by 38% for TerraZyme-stabilized samples and 39% for Road Stabilizr-stabilized samples relative to unstabilized controls. These results indicate that enzymatic stabilization strengthens interparticle bonding, reducing susceptibility to freeze–thaw weakening and promoting significant performance gains under cold-region conditions. The findings highlight the potential of enzyme treatments to improve the durability of soils in frost-prone infrastructure applications.