Significantly improving microbially induced carbonate precipitation (MICP) performance by the joint effect of polyaspartic acid and poly-lysine

This study pioneers the synergistic application of polyaspartic acid (PAsp) and poly-lysine (PLys) as dual polypeptide additives to enhance microbially induced calcium carbonate precipitation (MICP) for sand consolidation. Capitalizing on their complementary charge properties—anionic PAsp chelates Ca 2+ ions while cationic PLys bridges microbial cells to sand grains—this novel formulation significantly optimizes biocementation efficiency. For practical implementation, limestone waste-derived calcium acetate reduced material costs by 32 % versus conventional calcium chloride. At the optimal 5:5 PAsp:PLys ratio (100 mg/L total concentration), MICP-treated samples exhibited exceptional performance improvements:212.50 % increase in unconfined compressive strength,68.43 % higher CaCO₃ content,57.28 % reduction in permeability, and the dry density enhanced by 25.65 % compared to the samples without polypeptide with only 3 % additional treatment cost. ESEM/XRD analysis revealed vaterite-dominated crystallization with tunable morphology via polypeptide ratio adjustment. This cost-effective strategy demonstrates high potential for field implementation in desertification control and geotechnical reinforcement of erosion-prone slopes, embankments, and roadbeds. • Novel combination of polyaspartic acid (PAsp) and poly-lysine (PLys) enhances MICP performance for soil improvement. • Optimal 5:5 PAsp and PLys ratio increases unconfined compressive strength by 212.50 % and calcium carbonate content by 68.43 %. • Permeability was reduced by 57.28 %, and dry density improved by 25.65 % with the addition of polypeptides. • Use of calcium acetate from limestone waste cuts MICP costs by 32 %, making the process more sustainable. • Crystal analysis shows vaterite as the main form of calcium carbonate, with morphology varying by polypeptide concentration.