Concrete has a tendency to spall, that is, to eject layers when subjected to high temperatures. This is an erratic phenomenon, and our understanding of the underlying physical process is still limited. A driving process is moisture transfer, whose experimental investigation has so far mostly been limited to macroscopic or point‐wise observations, limiting both our understanding and the validation of the proposed models. In this paper, a non‐contact technique, neutron imaging, is used to extract a the full‐field distribution of moisture in 3D and in real time, while the concrete is heated at high temperatures. This reveals a number of processes often underestimated or ignored in the traditional experimental approaches reported in the literature. Notably, the effect on the evolving moisture profiles of varying heating rates for multiple insulation techniques as well the strong influence of the addition of spalling‐mitigating additives is presented. The first ever example of neutron tomography of a spalled sample is also reported, and some preliminary analyses of the effect that moisture clog formation and heating rates have on it are revealed.

中文翻译：

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通过快速中子层析定量分析温度梯度下混凝土样品中不断变化的水分分布：边界条件，湿热负荷历史和剥落减轻添加剂的影响

混凝土易于剥落，即在高温下会弹出层。这是一种不稳定的现象，我们对基本物理过程的理解仍然有限。一个驱动过程是水分转移，到目前为止，其实验研究主要限于宏观或逐点观察，这限制了我们对所提出模型的理解和验证。在本文中，当混凝土在高温下加热时，采用非接触技术（中子成像）以3D实时提取水分的全场分布。这揭示了文献中报道的传统实验方法中经常低估或忽略的许多过程。值得注意的是 提出了多种保温技术对不同加热速率对不断变化的水分分布的影响，以及添加了减少剥落的添加剂的强烈影响。还报道了剥落样品的中子断层成像的第一个例子，并且揭示了对水汽阻塞和加热速率对其影响的一些初步分析。