Quantitative measurement of the influence of degree of saturation on ion penetration in cement paste by using X-ray imaging
Quantitative measurement of the influence of degree of saturation on ion penetration in cement paste by using X-ray imaging
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DOI：
10.1016/j.conbuildmat.2017.03.007
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发表时间：
2017-06
影响因子：
7.4
通讯作者：
Mehdi Khanzadeh Moradllo;M. Tyler Ley
中科院分区：
文献类型：
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作者：
Mehdi Khanzadeh Moradllo;M. Tyler Ley
离子在混凝土中的外部渗透对混凝土结构的长期耐久性起着重要的作用。此外，膏体的饱和度（DoS）对流体渗透到混凝土中的速度和机制有很大的影响。人们对流体渗透到这些材料中的动态过程知之甚少，因为很少有实验技术能够在不损坏样品的情况下对流体运动进行定量的空间测量。本文利用实验室透射x射线显微镜（TXM）研究了在四种不同相对湿度（RH）条件下，水灰比为0.40的碘化物基示踪剂对水灰体的原位渗透。该技术可以在几分钟内以8.8 μm的分辨率对溶解离子的分布进行无损成像。此外，使用微x射线荧光（µXRF）成像和常规重量测量来比较I和Cl的渗透率，并验证TXM的结果。已经提出了数学模型来解释离子在部分饱和样品中的渗透。结果表明，在35%和70% RHs条件下（DoS分别为40.8%（±0.1%）和68.8%（±0.5%））浸泡2 d的样品，其渗透系数比饱和样品分别提高了40倍和10倍。此外，从TXM的浓度谱中观察到有关联合离子传输机制的重要见解。
The external penetration of ions into concrete plays an important role in long-term durability of concrete structures. In addition, the degree of saturation (DoS) of the paste has a large impact on rate and mechanisms of fluid penetration into concrete. There is little knowledge of the dynamic process of fluid penetration into these materials because few experimental techniques are able to give quantitative spatial measurements of the fluid movement without damaging the sample. This paper uses laboratory transmission X-ray microscopy (TXM) to investigate the in-situ penetration of an iodide based tracer into cement paste with water-to-cement ratio of 0.40 conditioned at four different relative humidities (RH). This technique can non-destructively image the distribution of the dissolved ions at 8.8 μm resolution in minutes. In addition, micro X-ray fluorescence (µXRF) imaging and conventional gravimetric measurements were used to compare I and Cl penetration rate and validate the results from TXM. Mathematical models have been proposed to account for ion penetration in partially-saturated samples. The results show that samples that were ponded for two days after being conditioned in 35% and 70% RHs (DoS of 40.8% (±0.1%) and 68.8% (±0.5%) respectively) show a 40× and 10× increase respectively in the penetration coefficient over the saturated sample. Furthermore, important insights about combined ion transport mechanisms have been observed from concentration profiles by TXM.