Optimization of enzyme-induced carbonate precipitation for Yellow River silty sand stabilization: A strategy combining urease inhibitor regulation and pre-mixing process

Abstract

Enzyme-induced carbonate precipitation (EICP) represents a promising technique for the stabilization of sand, however, the excessive activity of urease often leads to non-uniform carbonate precipitation, thus limiting its field applicability. To address these challenges, this study introduces a strategy that integrates urease inhibitor regulation with a pre-mixing approach. The results demonstrate that N-(n-butyl) thiophosphoric triamide (NBPT) at an optimal dosage of 0.1% relative to the mass of urea effectively slows urea hydrolysis. Mechanical testing reveals that sand columns treated with 0.1% NBPT exhibit the highest UCS, attributable to the enhanced uniformity of calcium carbonate distribution achieved through one-directional grouting. This finding is supported by mercury intrusion porosimetry. Microstructural analyses indicate that NBPT stabilizes vaterite and fosters its synergistic coexistence with calcite, thereby enhancing pore-filling efficiency and interparticle cementation. Notably, pre-mixing experiments show that 0.1% NBPT extends the workable pre-mixing time to 300 min, decreases post-curing surface hardness by 40%, and effectively prevents the formation of dense surface carbonate crusts, thereby enhancing constructability and suitability for vegetation. Rainfall erosion tests further confirm that NBPT-assisted mixed spraying reduces the mass loss of sandy slopes by approximately 18%. Collectively, this study delineates a controllable and engineering-oriented approach for large-scale EICP-based sand stabilization.

Graphical abstract

Keywords

urease inhibitor / EICP / soil stabilization / NBPT / sand improvement

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