Free and bound chloride relationships affecting reinforcement cover in alkali activated concrete
Free and bound chloride relationships affecting reinforcement cover in alkali activated concrete
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DOI：
10.1016/j.cemconcomp.2020.103692
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发表时间：
2020-09
影响因子：
10.5
通讯作者：
P. Mangat;Olalekan O. Ojedokun
中科院分区：
文献类型：
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作者：
P. Mangat;Olalekan O. Ojedokun
本文研究了碱活化混凝土（AACM）和对照硅酸盐水泥（PC）混凝土的游离氯离子分布、扩散参数和氯离子结合力。采用不同活化剂摩尔浓度的Ggbs基AACM混凝土试样，在5% NaCl溶液中暴露540天，测定其自由氯离子扩散特性。采用Freundlich等温线和Langmuir等温线测定了游离氯离子浓度和结合氯离子浓度之间的关系。为满足游离氯化物和束缚氯化物浓度的极限阈值，推导了防腐蚀所需的钢筋覆盖层。结果表明，菲克第二扩散定律适用于AACM混凝土的游离氯离子剖面，其扩散系数值高于同级别的PC混凝土。自由氯化物和束缚氯化物之间的关系由朗缪尔等温线确定。PC混凝土对水溶性氯化物和酸溶性氯化物的结合能力均高于AACM混凝土。当使用结合氯离子浓度阈值限值计算时，AACM比PC混凝土需要更少的混凝土覆盖钢筋。在AACM混凝土中，基于相应的自由氯离子限值的覆盖值高于其束缚氯离子值。
This paper investigates the free chloride profiles, diffusion parameters and chloride binding capacity of an alkali activated concrete (AACM) together with a control Portland cement (PC) concrete. Ggbs based AACM concrete specimens with different molarity of activator were exposed to a 5% NaCl solution for 540days to determine their free chloride diffusion properties. The relationships between the free and bound chloride concentration were determined by applying Freundlich and Langmuir isotherms. The required cover to steel reinforcement for corrosion prevention is derived to satisfy the limiting thresholds of free and bound chloride concentrations.The results show that Fick's second law of diffusion applies to the free chloride profiles of AACM concrete and provides higher values of diffusion coefficients than a similar grade of PC concrete. The relationship between the free and bound chlorides is defined by the Langmuir isotherm. PC concrete has higher chloride binding capacity than AACM concrete for both water and acid soluble chlorides. Less concrete cover to steel reinforcement is required in AACM than PC concrete when calculated by using the bound chloride concentration threshold limit. The values of cover based on the corresponding free chloride limit in AACM concrete are higher than its bound chloride values.