Mechanism of sulfate attack: A fresh look Part 1: Summary of experimental results
Mechanism of sulfate attack: A fresh look Part 1: Summary of experimental results
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DOI：
10.1016/s0008-8846(02)00724-x
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发表时间：
2002-06-01
影响因子：
11.4
通讯作者：
Olek, J
中科院分区：
文献类型：
--
作者：
Santhanam, M;Cohen, MD;Olek, J
本文研究了硫酸钠和硫酸镁溶液对不同类型硅酸盐水泥砂浆的膨胀和微观结构的影响。文中还报道了使用不同浓度硫酸盐和使用不同温度的效果。结果表明，砂浆在硫酸钠溶液中的膨胀经历了两个阶段。在初始阶段，阶段1，几乎没有扩张。第二阶段的膨胀突然而迅速地增加。微观结构研究表明，第二阶段的膨胀开始对应于砂浆内部化学未改变的裂缝的出现。超过这一点，膨胀几乎以恒定的速度进行，直到砂浆试件完全变质。在硫酸镁侵蚀的情况下，膨胀以持续增加的速度发生。显微结构研究表明，在将样品引入溶液后，表面几乎立即形成一层水镁石(氢氧化镁)。然后，硫酸盐离子在水镁石表面屏障上的稳定扩散控制着这种侵蚀。试件的最终失效是由于水合硅酸钙(C-S-H)的脱钙，并在长时间暴露于溶液后转化为水合硅酸镁(M-S-H)。文中还总结了不同外加剂的使用以及改变实验变量如溶液的温度和浓度的影响。硫酸钠和硫酸镁溶液引起的攻击机制的模型将在埃尔塞维尔科学有限公司出版的第二部分(C)2002中介绍。
This paper reports the results of an investigation on the effects of sodium and magnesium sulfate solutions on expansion and microstructure of different types of Portland cement mortars. The effects of using various sulfate concentrations and of using different temperatures are also reported. The results suggest that the expansion of mortars in sodium sulfate solution follows a two-stage process. In the initial stage, Stage 1, there is little expansion. This is followed by a sudden and rapid increase in the expansion in Stage 2. Microstructural studies suggest that the onset of expansion in Stage 2 corresponds to the appearance of cracks in the chemically unaltered interior of the mortar. Beyond this point, the expansion proceeds at an almost constant rate until the complete deterioration of the mortar specimen. In the case of magnesium sulfate attack, expansion occurs at a continually increasing rate. Microstructural studies suggest that a layer of brucite (magnesium hydroxide) on the surface forms almost immediately after the introduction of the specimens into the solution. The attack is then governed by the steady diffusion of sulfate ions across the brucite surface barrier. The ultimate failure of the specimen occurs as a result of the decalcification of the calcium silicate hydrate (C-S-H), and its conversion to magnesium silicate hydrate (M-S-H), after prolonged exposure to the solution. The effects of using various admixtures, and of changing the experimental variables such as the temperature and concentration of the solution, are also summarized in this paper. Models for the mechanism of the attack resulting from sodium and magnesium sulfate solutions will be presented in Part 2. (C) 2002 Published by Elsevier Science Ltd.