Developing new cementitious materials through mineral carbonation attracts increasing attention for reducing carbon emissions. However, the role of CaCO phase transition in the strength development of carbonated composites is not clear. In this study, new carbonated wollastonite composites are prepared and sodium tripolyphosphate (STPP) is used as a phase-controlling additive for the phase transition evolution of CaCO polymorphs during the carbonation process. Moreover, mechanical performance, microstructure, and carbonation mechanism are investigated. Results show that STPP is effective in enhancing mechanical performance by controlling CaCO phase transition. Specifically, STPP prolongs the phase transition of amorphous calcium carbonate (ACC) until 72 h later (the control binder at 1 h), allowing more opportunities for structural rearrangement. Besides, the introduction of STPP results in the formation of more stable ACC, vaterite, and aragonite, causing a compact microstructure and a lower carbonation degree. More importantly, STPP concentration within 0.3 M strongly improves the cementitious performance of all carbonated products (2.65–4.14 MPa/%), contributing to compressive strength growth (11.10–83.71%). The 0.1 M STPP-containing binder exhibits the highest compressive strength of 75.59 MPa. Our results contribute to unique pathways toward understanding the carbonation mechanism and a more sustainable cement industry.

中文翻译：

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了解三聚磷酸钠引起的碳酸硅灰石复合材料的 CaCO3 相变：从无定形到结晶

通过矿物碳化开发新型胶凝材料对于减少碳排放引起了越来越多的关注。然而，CaCO相变在碳酸复合材料强度发展中的作用尚不清楚。在这项研究中，制备了新型碳酸化硅灰石复合材料，并使用三聚磷酸钠（STPP）作为相控添加剂，用于碳酸化过程中碳酸钙多晶型物的相变演化。此外，还研究了机械性能、微观结构和碳化机理。结果表明，STPP 通过控制 CaCO 相变有效提高机械性能。具体来说，STPP 将无定形碳酸钙 (ACC) 的相变延长至 72 小时后（对照粘合剂为 1 小时），从而提供更多的结构重排机会。此外，STPP的引入导致形成更稳定的ACC、球霰石和文石，从而导致致密的微观结构和较低的碳化度。更重要的是，0.3 M 以内的 STPP 浓度极大地提高了所有碳酸产品的胶凝性能 (2.65–4.14 MPa/%)，有助于抗压强度增长 (11.10–83.71%)。含0.1 M STPP 的粘合剂表现出最高的抗压强度，为75.59 MPa。我们的研究结果有助于为了解碳化机制和更可持续的水泥行业提供独特的途径。