Mineralization of Low-Carbon Bio-carbonate, Bio-phosphate, and Bio-composite Cements

Ordinary Portland cement (OPCOrdinary portland cement (OPC)) emits a lot of carbon dioxideCarbon dioxide during the production process. The production of 1 ton of OPCOrdinary portland cement (OPC) emits about 0.8 tons of carbon dioxideCarbon dioxide. Microbial cementMicrobial cement emits no or a small amount of carbon dioxideCarbon dioxide and belongs toLow-carbon bio-cement low-carbon bio-cement. Hence, three types of bio-cementsBiocement are prepared to partially replace OPCOrdinary portland cement (OPC). Growth curvesGrowth curves of carbonate-mineralization microbeCarbonate-mineralization microbe (CMM) and phosphate-mineralization microbePhosphate-mineralization microbe (PMM) (PMM) show that the breeding processBreeding process of microbes becomes relatively stable and slow after 20 h. SizeSize and morphologyMorphology of bio-carbonateBio-carbonate cement and bio-phosphate cementsBio-phosphate cement can be regulated by pure waterWater, bacterial bodyBacterial body, bacterial secretionBacterial secretion, and bacterial solutionBacterial solution. AmmoniaAmmonia/ammoniumAmmonium \(({\mathrm{NH}}_{3}/{\mathrm{NH}}_{4}^{+})\) can well be converted into environment-friendly carbonateCarbonates and struviteStruvite precipitationPrecipitation when \({\mathrm{HPO}}_{4}^{2-}\) and \({\mathrm{Mg}}^{2+}\) are contained in the mixtureMixture solution of CMMCarbonate-mineralization microbe and ureaUrea in the production process of the bio-composite cementBio-composite cement. The shapeShape of bio-CaCO3, bio-BaHPO4, and bio-composite cementBio-composite cement crystalsCrystal are mainly sphericalSpherical, dumbbellDumbbell, and irregular blockIrregular block structuresStructure with different sizesSize in bacterial solutionBacterial solution, respectively. However, the shapeShape of their crystalsCrystal between sandSand particles is mainly ballBall, dumbbellDumbbell, and irregular blockIrregular block clusterCluster structuresStructure with different sizesSize, respectively. Therefore, the morphologyMorphology of these crystalsCrystal in bacterial solutionBacterial solution is different from that in sandSand environmentEnvironment. Bacterial solutionBacterial solution and sandSand particle play an important role in the nucleationNucleation, growthGrowth, and accumulation of crystalsCrystal for bio-CaCO3, bio-BaHPO4, and bio-composite cementsBio-composite cement. PoresPore of loose sandSand columns can well be filled by bio-CaCO3, bio-BaHPO4, and bio-composite cementsBio-composite cement.