In order to better understand the physics of bursting concrete, Empa researchers and a team from the University of Grenoble and the Laue-Langevin Institute, also in Grenoble, have for the first time used neutron tomography to produce three-dimensional images of the interior of heated concrete in real time. The investigations were only possible thanks to the strong neutron source at the Laue-Langevin Institute. The scientists took up to 500 pictures per minute and constructed a unique three-dimensional model of the spalling concrete.
So far experts have only been able to conclude that water in concrete moves away from a heat source and accumulates. The moisture would thus act as a barrier and would prevent water vapor from escaping. Therefore, the vapor pressure would rise to the extent that the material would have no choice but to explode. Using the new experimental setup, the Empa researchers and their colleagues could now actually observe this moisture barrier.
The drying front can be clearly seen on the neutron image. Image: Sciencedirect
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