与钢筋脱钝化临界孔溶液pH值相关联的混凝土碳化理论模型

通过分析混凝土可碳化物质来源,认为抗碳化能力的关键是在孔溶液中电离形成的OH-总量.讨论了混凝土碳化过程孔溶液碱度变化与孔溶液氢氧根离子形成过程的关系.在Papadakis碳化模型的基础上提出了与钢筋脱钝化临界孔溶液pH值相关联的可用于大掺量工业废渣混凝土及含氯盐混凝土改进的碳化理论模型.应用模型对3个水胶比(以质量计,下同)的普通混凝土和掺25%矿渣和25%粉煤灰混凝土的碳化值进行了理论计算,计算结果与加速碳化试验的结果比较分析表明:改进的碳化理论模型对于大掺量工业废渣混凝土具有相对好的准确性,同时分析表明该模型对于含氯盐混凝土也具有良好的适应性,从而为大气环境下掺工业废渣混凝土和含氯盐混凝土的耐久性设计和使用寿命预测提供了新的方法和途径.

THEORETICAL CARBONATION MODEL RELATED WITH PORE SOLUTION pH VALUE FOR STEEL BAR DEPASSIVATION IN CONCRETE

Based on an analysis of the component source of carbonatable substance in concrete, the source of carbonatable substance in concrete essentially is the total quantity of hydroxyl ions ionized in pore solution. The relationship between the variation of the alkalinity of pore solution in the carbonation process and formation process of hydroxyl ions ionized in pore solution is discussed, and an improved concrete carbonation theoretical model is recommended. The proposed model is related to the critical pH value for steelbar depassivation of concrete pore solution based on the Papadakis carbonation model, which can be applicable to normal concrete, concrete with high content industrial waste residue as well as concrete contaminated with chloride. The theoretical carbonation depths of normal concrete and concrete with 25% slag and 25% fly ash added with different mass ratios of water to binder were calculated using this model. Comparison of the results of the calculation data and experimental data indicate that the improved ccrbonation model not only has relatively good accuracy for concrete with high content industrial waste residue but also has better adaptability for concrete contaminated with chloride. So a new method for the durability design and service life prediction of concrete with high content industrial waste residue and concrete contaminated with chloride in an atmospheric environment is provided.