This experimental and numerical study aims to evaluate the penetration depth of contaminated water in the concrete structures involved in the Fukushima Daiichi nuclear powerplant. The influence of the mortar mixture on water absorption was investigated by varying the composition: mortar containing aggregates from river sand and crushed limestone sand was compared, and 15% of the cement in the mixture was substituted with fly ash. The effect of temperature in nuclear conditions is also significant; therefore, water uptake at temperatures of 20 and 60°C was considered. Finally, pre-drying conditions were studied by drying the sample at two different conditions: at 105°C and at 40% RH (relative humidity) and 20°C. Water uptake was monitored using x-ray computed radiography in combination with mass measurements. In all cases, anomalous sorption, or a nonlinear relationship between penetration depth and the square root of exposure time was observed, with the sorption curves showing bimodal behavior. The aggregate type had no significant effect on the water uptake results. However, the samples containing fly ash clearly had lower water uptake rates, which can be explained by the differences in the calcium silicate hydrate (C-S-H) structures. With increasing temperature, the penetration was slightly accelerated at the beginning of the experiment, with the rate of penetration then decreasing rapidly. The densification of C-S-H at higher temperatures could contribute to this phenomenon. Microstructural rearrangements can also explain why the highest uptake rates occurred for samples that were exposed to severe drying conditions (105°C). The experimental results were consistent when the microstructural rearrangement was considered, further confirming these conclusions.

这项实验和数值研究旨在评估福岛第一核电站所涉及的混凝土结构中污水的渗透深度。通过改变组成来研究砂浆混合物对吸水率的影响：比较了砂浆中含有来自河砂和碎石灰石砂的骨料，并用粉煤灰代替了混合物中15％的水泥。温度在核条件下的影响也很明显。因此，考虑了在20和60°C的温度下的吸水率。最后，通过在两种不同的条件下干燥样品来研究预干燥条件：在105°C和40％RH（相对湿度）和20°C下干燥。使用X射线计算机射线照相术结合质量测量监测吸水率。在所有情况下，异常吸附 或观察到渗透深度与暴露时间的平方根之间存在非线性关系，吸附曲线显示出双峰行为。骨料类型对吸水率没有显着影响。但是，含有粉煤灰的样品显然具有较低的吸水率，这可以通过水合硅酸钙（CSH）结构的差异来解释。随着温度的升高，渗透率在实验开始时略有加速，但渗透率随后迅速下降。高温下CSH的致密化可能是造成这种现象的原因。微观结构的重排也可以解释为什么暴露在严峻干燥条件下（105℃）的样品吸收率最高。