Experimental Study on the Mechanical Property Improvement of MICP by Adding Different Polysaccharide Polymers

The low mechanical properties of microbially induced calcium carbonate precipitation (MICP) significantly hinder the engineering application of this technology. Four polysaccharide polymers, including low-viscosity hydroxypropyl methylcellulose (HPMC-LV), high-viscosity hydroxypropyl methylcellulose (HPMC-HV), carboxymethyl cellulose (CMC), and carboxymethyl chitosan (CMCH), were added in the MICP processes to investigate their effects on the mechanical properties of precipitated calcium carbonate. By comparing the crystalline phase of calcium carbonate, particle morphology and size, and pore structure of precipitates with and without the polysaccharide polymers, the underlying mechanisms were revealed for the enhancement effect of polysaccharide polymers on the mechanical properties of the precipitates. The results show that (1) the addition of CMC or CMCH significantly increases the average hardness and Young’s modulus of the precipitated calcium carbonate, whereas the addition of HPMC-LV or HPMC-HV has no significant effect; (2) the addition of HPMC-LV or HPMC-HV tends to increase the proportion of calcite and improve the pore structure in the precipitates, whereas the addition of CMC or CMCH tends to increase the particle size; and (3) compared with HPMC-LV and HPMC-HV, CMC and CMCH can better induce the mixing of organic-inorganic materials and promote more easily the aggregation and growth of particles. This is because CMC and CMCH are rich in carboxyl group, whereas HPMC-LV and HPMC-HV are rich in hydroxyl group. The carboxyl group has a stronger electrostatic interaction than does the hydroxyl group. This work is conducive to promoting the engineering application of MICP technology.