Carbonation enhancement of C(3)S(2) by carbonic anhydrase-producing bacteria: Performance, microstructure, and mechanism.

CA-producing bacteria at 2.0% dosage markedly enhance C3S2 carbonation, yielding 51.7 MPa 7-day compressive strength and 19.68 wt% CO2 sequestration efficiency.

• Why it matters: Rankinite (C3S2) carbonation is limited by slow kinetics and extra energy needs in conventional accelerated curing, reducing the practicality of CO2 mineralization for construction materials.
• What they did: CA-producing bacteria were added to C3S2 specimens, and mechanical performance, CO2 sequestration, phase evolution (XRD/FT-IR), and pore/microstructure (X-CT, MIP, nanoindentation, SEM) were systematically measured.
• The result: Bacterial incorporation promoted early carbonation, increased carbonation depth, refined pore structure, and shifted CaCO3 polymorphs toward higher aragonite and vaterite, consistent with CA-catalyzed CO2 hydration plus nucleation and pore-filling by cells and solid carriers.

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