Conduction, relaxation and complex impedance studies on Portland cement mortars during freezing and thawing
Conduction, relaxation and complex impedance studies on Portland cement mortars during freezing and thawing
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DOI：
10.1016/j.coldregions.2019.102819
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发表时间：
2019-10-01
影响因子：
4.1
通讯作者：
McCarter, W. John
中科院分区：
文献类型：
--
作者：
Kim, Jaehwan;Suryanto, Benny;McCarter, W. John
在20 Hz-1 MHz带宽范围内测量了冻融对波特兰水泥砂浆复电阻抗的影响。将样品暴露于-70 ℃至+20 ℃范围内的循环温度状态。除了奈奎斯特图，体电导率和介电常数从阻抗测量中被解嵌，并在频域中呈现，以研究冰的形成/融化，以及其对毛细管和凝胶孔网络内的传导和极化过程的影响。体离子传导和极化过程的活化能也建立了使用阿罗修斯关系，它表明，滞后存在于热循环的一个重要部分。在存在滞后效应的情况下，样品的电导率在循环的解冻部分比在冷冻部分低。它还表明，当体积电导率在阿氏格式，四个不同的区域被确定在循环的冷却部分，而在循环的加热部分，只有两个区域存在。结果表明，耗散传导过程对整体传导的贡献随着温度的降低和频率的增加而增加。的水/水泥比示出有显着的影响，复阻抗测量，孔隙水和活化能的冰点和熔点的抑郁症。
The influence of freezing and thawing on the complex electrical impedance of Portland cement mortars is presented with measurements obtained over the bandwidth 20 Hz-1 MHz. Samples were exposed to a cyclic temperature regime within the range - 70 degrees C to + 20 degrees C. In addition to Nyquist plots, the bulk conductivity and permittivity were de-embedded from the impedance measurements and presented in the frequency domain to study ice formation/thawing, and its influence on conduction and polarisation processes within the capillary and gel pore network. The activation energy for bulk ionic conduction and polarisation processes was also established using an Arrhenius relationship and it was shown that hysteresis was present over a significant portion of the thermal cycle. Where hysteresis effects were present, the conductivity of the sample was lower on thawing portion of the cycle than on the freezing. It was also shown that when the bulk conductivity was presented in an Arrhenius format, four distinct regions were identified on the cooling part of the cycle, whereas on the heating part of the cycle only two regions were present. It was found that the contribution of dissipative conduction processes to the overall conduction increased with decreasing temperature and with increasing frequency. The water/cement ratio is shown to have a significant influence on complex impedance measurements, the depression in freezing and melting point of the pore-water and activation energy.