Preparation and Properties of Pine Powder-Bacillus pasteurii Microspheres

Aiming at the problems of low survival rate and weak mineralization activity of microorganisms in the high- alkali and high- shear environment of concrete, pine powder and nanomaterials were used as composite carriers to prepare Bacillus pasteurii microspheres by embedding method. The optimal culture conditions of microorganisms were determined by single factor experiments, the mix ratio of microspheres was optimized by orthogonal design, and systematic characterization was carried out from physical properties, mechanical strength, microscopic morphology and phase composition. The results show that the growth and urease activity of Bacillus pasteurii are optimal when the culture temperature is 30℃, initial pH=7, inoculation amount is 2%, and culture time is 24h; the optimal mass ratio of pine powder, nanomaterials and bacterial solution is 1:1:3, at this time, the average particle size of microspheres is 2.1±0.3mm, the embedding rate is 91.6%, the 24h bacterial burst release rate is less than 8.5%, and the mass loss rate after shaking for 24h is only 2.35%; SEM and XRD confirm that the microspheres form a porous composite structure, where microorganisms colonize well and can induce the formation of calcite-type calcium carbonate. The microspheres can effectively protect the bacteria and meet the application requirements of concrete self-healing.