Moisture transport in concrete during fire as studied by NMR

NMR imaging of moisture in concrete is a valuable tool for monitoring changes in the moisture content of concrete, e.g., during drying, dehydration, and heating. It can be a useful tool in assessing the consequences of certain environmental conditions non-destructively. We present combined moisture content and temperature profiles of one-sided heated concrete samples measured with our dedicated NMR setup. The concrete sample was equilibrated at a moisture content of 97 % RH. The moisture content can be measured quantitatively and nondestructively while heating up the sample one sided to 500°C. We present the first experimental proof for the built up of a moisture peak in concrete, and the formation of a saturated layer. The temperatures meausured at the boiling front indicate a vapour pressure in the order of 1.8 MPa. A simple vapour transport model was successfully used to describe the speed of the boiling front