Field-scale bio-cementation tests to improve sands

Abstract

Microbially induced calcite precipitation (MICP) is a bio-mediated cementation process that improves the geotechnical properties of soils through the precipitation of calcite at soil particle contacts. This study presents a field-scale, surficial application of MICP to improve the erosion resistance of loose sand deposits and provide surface stabilisation for dust control and future re-vegetation. Three test plots were treated with a bacterial culture and nutrient solutions at varying concentrations, and a fourth test plot served as a control. Improvement was assessed to a depth of 40 cm using dynamic cone penetration (DCP) testing and calcite content measurements. The most improved test plot received the lowest concentrations of urea and calcium chloride and developed a stiff crust measuring 2·5 cm thick, which exhibited increased resistance to erosion. DCP testing and calcite content measurements indicated improvement to a depth of approximately 28 cm near the targeted depth of 30 cm. The results suggest that further optimisation of solutions and techniques could render MICP viable for larger-scale applications.