In this study, optical pH imaging was compared to phenolphthalein coloration and mineralogical analyses to enhance the comprehension of carbonation mechanisms in blended cements. Mortar mixes with four different binders were cured both sealed and underwater before being tested at 2 % CO2, 65 % RH for up to 91 days. With its high spatial resolution capability, pH imaging facilitated the quantification of pH within the range of 6.5 to 12.0. The optical pH imaging revealed that the pH in the carbonated regions ranged from <9.5 to 11.9 which indicates significant differences in the corrosion risk. Additionally, the pH at the phenolphthalein endpoint (= colour change) was higher than commonly presumed within a range of 10.3 to 11.9. The correlations obtained between mineralogy and pH changes during carbonation highlight the combined effect of the clinker content and the curing regime not only on the carbonation rate but also on the carbonation degree.

中文翻译：

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光学 pH 成像揭示了酚酞隐藏的内容 – 混合水泥的碳化研究


在这项研究中，将光学 pH 成像与酚酞着色和矿物学分析进行了比较，以增强对混合水泥中碳化机制的理解。含有四种不同粘合剂的砂浆混合物在密封和水下固化，然后在 2% CO2、65% RH 下测试长达 91 天。凭借其高空间分辨率能力，pH 成像有助于在 6.5 至 12.0 范围内定量 pH 值。光学 pH 成像显示，碳酸盐区的 pH 值范围为 <9.5 至 11.9，表明腐蚀风险存在显著差异。此外，酚酞终点的 pH 值（= 颜色变化）高于通常假设的 10.3 至 11.9 范围内。矿物学和碳酸化过程中 pH 值变化之间的相关性突出了熟料含量和固化机制的综合影响，不仅对碳酸化速率，而且对碳酸化程度。