混凝土碳化深度酚酞与pH测试值的相关性研究

Correlation study of concrete carbonation depth values tested by phenolphthalein and pH value

针对现有酚酞测量碳化深度的方法无法界定不完全碳化区的不足,采用模拟孔溶液法研究了不同温度、湿度和二氧化碳浓度条件下混凝土碳化区域的分布,认为混凝土模拟孔溶液与真实孔溶液的pH值不同,但可反映出真实孔溶液pH值的变化趋势,并给出了混凝土完全碳化区内表层较内层模拟孔溶液pH值偏大的原因。考虑骨料分布差异,提出了基于模拟孔溶液pH值界定混凝土完全和不完全碳化区域的方法,建立了基于模拟孔溶液的碳化混凝土pH值分布模型。将依模拟孔溶液pH值曲线界定的完全碳化区终点深度和不完全碳化区终点深度与酚酞测试无色区深度对比,结果表明,混凝土碳化深度酚酞测试值介于完全和未完全碳化深度之间,其值约为完全碳化区长度的2倍。

Because that incomplete carbonation zone cannot be defined by the existing phenolphthalein method for carbonation depth measurement, simulated pore solution method was used to study the zone distribution of concrete carbonation under the condition of different temperature, humidity and CO2 concentration. It is considered that pH value of simulated pore solution is different from that of real pore solution ,but the variation trend of pH value in the real pore solution can be reflected.Simulated pore solution pH value of the sur- face layer is greater than the inner in the completely concrete carbonization zone, and the reason is given.Considering the difference of aggregate distribution, definition method of concrete complete and incomplete carbonation zone based on the pH value of simulated pore solution is put forward, and pH profile model of carbonated concrete based on the simulation pore solution is established.Compared com- plete and incomplete carbonation zone depth based on the simulated pore solution pH curve with that based on the colorless zone depth tested by phenolphthalein, it is shown that concrete carbonation depth tested by phenolphthalein is between complete and incomplete carbonation depth, and its value is about 2 times more than that of complete carbonization zone.