Synergic effect of sodium alginate in the microbially induced calcium carbonate precipitation.

Microbially Induced Calcium Carbonate Precipitation (MICP) has emerged as an innovative and environmentally sustainable technique for construction material stabilization. However, its practical application is hindered by limitations such as non-uniform carbonate precipitation and low reaction efficiency. This study investigates the synergistic role of sodium alginate (SA), a natural polysaccharide, in enhancing MICP precipitation efficiency. Systematic experiments assessed how adding 1 wt% SA affected CaCO₃ precipitation across three cementation media (CM) designs (urea:Ca2+ ratios of 1:1, 1:2, 2:1). The result showed that SA significantly enhanced precipitate mass and CaCO3 yield across all CM designs and promotes vaterite formation and reduces crystallite size. The strongest enhancement in CaCO3 yield was observed at a urea:Ca2+ ratio of 1:2 (85% increase from the SA-free control). The precipitate from the same design shows dense and monolithic microstructures where the mineral particles are encapsulated, densely packed and cohesively connected through alginate matrix. These findings provide a novel perspective on optimizing MICP-based biocementation through biopolymer-assisted precipitation, advancing its potential for sustainable construction and soil stabilization applications.