When exposed to high temperatures, concrete is prone to explosive spalling, resulting in the projection of concrete flakes and the reduction of the structural element cross-section. Elastic energy alone cannot justify the explosive nature of the process: accumulated thermal energy serves as a supplementary source, together with the water in the pores, which can generate kinetic energy through vaporization. The objective of this paper is to study the fast thermal and hygral transients occurring upon depressurization of an internal interface, emulating a crack developing in hot moist concrete. One possible mechanism that could justify this contribution is the flash vaporization of water. This paper presents a new experimental approach to directly measure flash vaporization through rapid-neutron imaging. Additionally, a thermo-hygral model assesses key parameters influencing fast-transient phenomena. Experimental observations reveal moisture loss in a 1-mm-thick layer, equating to a 90 °C temperature drop, justifying a significant amount of released energy.

中文翻译：

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减压界面附近的快速蒸气迁移：中子成像揭示爆炸剥落的可能驱动机制

当暴露在高温下时，混凝土容易发生爆炸性剥落，导致混凝土片的突出和结构元件横截面的减小。仅靠弹性能并不能证明该过程的爆炸性：积累的热能作为补充源，与孔隙中的水一起可以通过蒸发产生动能。本文的目的是研究内部界面减压时发生的快速热瞬变和湿瞬变，模拟热湿混凝土中形成的裂缝。可以证明这种贡献的一种可能机制是水的闪蒸。本文提出了一种通过快中子成像直接测量闪蒸的新实验方法。此外，热湿模型评估影响快速瞬变现象的关键参数。实验观察显示，1 毫米厚的层中的水分损失相当于温度下降 90 °C，这证明释放大量能量是合理的。