This study investigates the effect of relative humidity (RH) on the carbonation of hydration products. The samples of ordinary Portland cement (OPC) and OPC/blast furnace slag paste were exposed to accelerated carbonation under 3% CO₂ concentration at different RHs from 11% to 85%. Thermogravimetric/differential thermal analysis and X-ray diffraction/Rietveld analysis were performed to quantify the amount of portlandite and calcium carbonate polymorphs. The Ca/Si ratio of the carbonated C-S-H phase was determined using a phase equilibrium calculation. To evaluate the microstructural changes in carbonated sample, water vapor sorption and nitrogen sorption measurements were conducted before and after carbonation. Results show that the carbonation shrinkage progressively increased at intermediate RHs (43% and 66% RH). The relation between carbonation shrinkage and the Ca/Si ratio of C-S-H agrees with the change of C-S-H mean chain length. There were significant changes in the carbonation rates of C-S-H and portlandite at different RHs. The coarsening of the meso scale pore likely derives from the polymerization and aggregation of C-S-H due to decalcification. This paper is an extended and enhanced version of an earlier study [Suda, Y., Tomiyama, J., Saito, T. and Saeki, T., (2020). “Impact of relative humidity on carbonation shrinkage and microstructure of hardened cement paste.” In: Proc. 6th International Conference on Construction Materials (ConMat'20), Fukuoka, Japan 27-29 August 2020. Tokyo: Japan Concrete Institute].

本研究调查了相对湿度 (RH) 对水合产物碳酸化的影响。普通硅酸盐水泥 (OPC) 和 OPC/高炉矿渣浆样品在 3% CO ₂下暴露于加速碳化不同相对湿度下的浓度从 11% 到 85%。进行热重/差热分析和 X 射线衍射/Rietveld 分析以量化硅酸盐和碳酸钙多晶型物的量。使用相平衡计算确定碳酸化 CSH 相的 Ca/Si 比。为了评估碳酸化样品的微观结构变化，在碳酸化之前和之后进行了水蒸气吸附和氮吸附测量。结果表明，碳化收缩在中等 RH（43% 和 66% RH）下逐渐增加。碳化收缩率与CSH的Ca/Si比的关系与CSH平均链长的变化一致。CSH和硅酸盐在不同RHs的碳化率有显着变化。中尺度孔隙的粗化可能是由于脱钙导致 CSH 的聚合和聚集。本文是早期研究 [Suda, Y., Tomiyama, J., Saito, T. 和 Saeki, T., (2020) 的扩展和增强版本。“相对湿度对硬化水泥浆体碳化收缩和微观结构的影响。” 在：过程 第六届国际建筑材料会议 (ConMat'20)，日本福冈，2020 年 8 月 27-29 日。东京：日本混凝土研究所]。