Assessing the impact of relative humidity (RH) on carbonation kinetics is crucial for the sustainable and high-strength advancement of CO2-activated Ca-bearing materials incorporating phase-controlling additives. This work focuses on the carbonation kinetics, mechanical properties, and microstructure evolution of carbonated wollastonite composites containing sodium tripolyphosphate (STPP) when exposed to various RH levels. Results show that RH plays an important role during the carbonation of wollastonite, functioning both as a reaction material and accelerating role for wollastonite carbonation. The carbonation rate and the phase transition reaction of poorly crystalline CaCO3 is accelerated at RH ranging from 70% to 95%, favouring to cementitious behaviour of CaCO3 and results in denser microstructure, especially for 85% RH. The carbonation reaction is composed of two distinct stages, namely, wollastonite dissolution and precipitation of the stage-1 and ion-diffusion controlling of stage-2. Among them, the addition of STPP prolong the carbonation duration of stage-1. The degree of carbonation (DOC) of the internal layer sample is higher than that of the outermost layer sample. CaCO3 and silica gel are evenly distributed indirectly, which reduces the elastic modulus at 85 % RH. However, regardless of RH, the cementitious efficiency of poorly crystalline CaCO3 is the highest, followed by calcite and silica gel. Consequently, STPP modified carbonated wollastonite shows highest strength when exposed to 85% RH (67.3 MPa at 7 days). Our study provides a unique way toward developing the STPP-containing carbonated wollastonite system for high performance carbonated materials.

中文翻译：

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相对湿度对含三聚磷酸钠的碳酸盐硅灰石复合材料碳化动力学和强度发展的影响


评估相对湿度 （RH） 对碳化动力学的影响对于结合相位控制添加剂的 CO2 活化 Ca-bearing 材料的可持续和高强度发展至关重要。这项工作的重点是含有三聚磷酸钠 （STPP） 的碳酸盐硅灰石复合材料在不同 RH 水平下下的碳化动力学、力学性能和微观结构演变。结果表明，RH 在硅灰石碳化过程中起着重要作用，既可以作为反应材料，又可以加速硅灰石碳化。在 70% 至 95% 的 RH 范围内，低结晶性 CaCO3 的碳化速率和相变反应加速，有利于 CaCO3 的胶凝行为，并导致更致密的微观结构，尤其是对于 85% RH。碳化反应由两个不同的阶段组成，即第一阶段的硅灰石溶解和沉淀以及第一阶段 2 的离子扩散控制。其中，STPP 的添加延长了第一阶段的碳酸化持续时间。内层样品的碳化度 （DOC） 高于最外层样品的碳化程度 （DOC）。CaCO3 和硅胶间接均匀分布，这降低了 85 % RH 时的弹性模量。然而，无论 RH 如何，低结晶 CaCO3 的水泥基效率最高，其次是方解石和硅胶。因此，STPP 改性碳酸盐岩硅灰石在暴露于 85% RH 时表现出最高的强度（7 天时为 67.3 MPa）。我们的研究为开发用于高性能碳酸盐材料的含 STPP 的碳酸盐硅灰石系统提供了一种独特的方法。