Damage mechanisms of two-stage concrete exposed to chemical and physical sulfate attack
Damage mechanisms of two-stage concrete exposed to chemical and physical sulfate attack
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DOI：
10.1016/j.conbuildmat.2017.01.112
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发表时间：
2017-04-15
影响因子：
7.4
通讯作者：
Azabi, T. M.
中科院分区：
文献类型：
--
作者：
Najjar, M. F.;Nehdi, M. L.;Azabi, T. M.
目前缺乏有关两阶段混凝土（TSC）的物理和化学硫酸盐暴露的耐久性的信息。TSC在许多方面不同于传统混凝土，包括其浇筑技术，高骨料含量和使用非常易流动的灌浆。因此，有关硫酸盐侵蚀下常规混凝土性能的现有数据可能不适用于TSC。例如，不同参数的影响，如添加辅助胶凝材料（SCM）的抗硫酸盐侵蚀的传统混凝土有据可查，但是，TSC这还没有得到应有的调查。在这项研究中，在硫酸钠的环境中的行为TSC混合物纳入不同的SCM作为普通波特兰水泥（OPC）的部分替代进行了研究。两种不同的硫酸钠暴露制度进行了研究：全浸泡模拟化学硫酸盐侵蚀，部分浸泡结合循环温度和相对湿度，这有利于物理盐侵蚀。完全浸没TSC标本纳入粉煤灰或Meta高岭土表现出高的抗硫酸盐性。令人惊讶的是，TSC标本纳入硅灰表现出显着的损害，由于碳硫硅钙石的形成。在暴露于物理盐的攻击下，TSC标本纳入粉煤灰和/或硅灰在蒸发前端发生严重的表面结垢，而那些与偏高岭土揭示了足够的抵抗表面结垢。人们试图描述解释这种观察到的行为的机制。(C)2017爱思唯尔有限公司版权所有
There is currently dearth of information on the durability of two-stage concrete (TSC) to physical and chemical sulfate exposure. TSC differs from conventional concrete in many ways including its placement technique, high aggregate content and the use of Very flowable grout. Therefore, available data on the behavior of conventional concrete under sulfate attack may not be applicable to TSC. For instance, the effects of different parameters such as the addition of supplementary cementitious materials (SCMs) on the resistance to sulfate attack are well documented for conventional concrete; however, for TSC this has not been duly investigated. In this study, the behavior in sodium sulfate laden environments of TSC mixtures incorporating different SCMs as partial replacement for ordinary Portland cement (OPC) was investigated. Two different sodium sulfate exposure regimes were studied: full immersion simulating chemical sulfate attack, and partial immersion combined with cyclic temperature and relative humidity, which is conducive to physical salt attack. Fully immersed TSC specimens incorporating fly ash or meta kaolin exhibited high sulfate resistance. Surprisingly, TSC specimens incorporating silica fume exhibited significant damage due to thaumasite formation. Under exposure to physical salt attack, TSC specimens incorporating fly ash and/or silica fume incurred severe surface scaling at the evaporative front, while those made with metakaolin unveiled adequate resistance to surface scaling. An attempt has been made to delineate the mechanisms which explain such observed behavior. (C) 2017 Elsevier Ltd. All rights reserved.