Mineral carbonation performance of wollastonite-blended cementitious composites through in-situ CO2 mixing

This study assessed the feasibility of in-situ CO2 mixing in a wollastonite-blended cementitious composite by evaluating its mineral carbonation performance. Wollastonite (CS) polymorphs were synthesized and used to replace ordinary Portland cement with up to 30 wt%. The results showed that amorphous CaCO3, calcite, and monocarboaluminate were formed as carbonation products. The wollastonite-blended cementitious composite with a 20 % replacement of beta-CS exhibited the highest CaCO3 production of 22.5 wt%, which was mainly attributed to amorphous CaCO3. beta-CS showed a superior mineral carbonation ability to alpha-CS because the Cadepleted silicate layer formed by the dissolution of beta-CS accelerated the formation of amorphous CaCO3. Moreover, CS retarded the early-stage formation of ettringite and monocarboaluminate by delaying gypsum dissolution. The wollastonite-blended cementitious composites exhibited superior compressive strength exceeding 40 MPa. These results demonstrate that the mineral carbonation of wollastonite-blended cementitious composite can be accomplished through in-situ CO2 mixing, especially with beta-CS replacement, which has significant potential as a CO2 storable binder.