Experimental study on effects of CO2 concentrations on concrete carbonation and diffusion mechanisms
Experimental study on effects of CO2 concentrations on concrete carbonation and diffusion mechanisms
复制标题
CO2浓度对混凝土碳化及扩散机制影响的实验研究
DOI：
10.1016/j.conbuildmat.2015.06.007
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发表时间：
2015-09-15
影响因子：
7.4
通讯作者：
Xing, Feng
中科院分区：
文献类型：
--
作者：
Cui, Hongzhi;Tang, Waiching;Xing, Feng
本文采用加速碳化试验方法，将不同等级的混凝土暴露于5种不同的CO2浓度水平（体积比为2、10、20、50和100%）中。研究了混凝土碳化深度与CO2浓度的关系。通过扫描电镜观察，分析了CO2气体在混凝土中的扩散机理。试验结果表明，在相同碳化年龄下，当混凝土试样暴露于较低的CO2浓度（2-20%）时，碳化深度的增加幅度较大；当样品暴露于高浓度二氧化碳（即50-100%）时，则较低。其原因主要是由于混凝土碳化引起的微观结构变化，使表层密度增大，从而降低了CO2向混凝土扩散的速度。SEM结果表明，碳化通过堵塞孔隙，减小孔隙尺寸，降低了混凝土的孔隙率。认为高、低CO2浓度下CO2在混凝土中的扩散机制不同。(C) 2015 Elsevier Ltd.版权所有。
In this paper, concretes of different grades were exposed to five different CO2 concentration levels (2, 10, 20, 50 and 100% by volume) using accelerated carbonation test methods. The relationship between the depth of concrete carbonation and CO2 concentration was investigated. The diffusion mechanisms of CO2 gas in concrete were analysed through the scanning electron microscopy (SEM) observations. Experimental results showed that, under the same carbonation age, the increase of carbonation depth was found to be high when concrete samples were exposed to low CO2 concentrations (i.e. 2-20%); and low when the samples were exposed to high CO2 concentrations (i.e. 50-100%). The reason for this is mainly due to the microstructure change caused by concrete carbonation, which makes the surface layer denser thus lowering the rate of CO2 diffusion into concrete. SEM results showed that carbonation decreased the porosity of concrete by clogging up the pores and reducing the pore sizes. It is believed that the diffusion mechanisms of CO2 into concrete under high and low CO2 concentration levels would be different. (C) 2015 Elsevier Ltd. All rights reserved.