Redistribution of pore water in the cement gel of concrete

Concerning water transport, concrete shows a behaviour deviating from most other mineral building materials. Besides processes in the concrete such as hydration and carbonization this behaviour is due to a clearly different pore volume. In addition to the capillary pores in all mineral building materials, this material also has diminutive gel pores. But at present, no measurement method is sufficiently exact for the direct measurement of the water contents in these pores. Measurement methods based on nuclear magnetic resonance (NMR) provide extremely low relaxation times due to the strong physical bond of water molecules. As a consequence, the hydrogen cores fall back into the initial position after termination of the excitation impulse, before the measurement signal can be detected. But it is exactly this effect, which can be used to measure the redistribution of the water from the capillary pores into the gel pores and to calculate transport coefficients for the computational modelling of this process. This may be a hint to explain the frequently observed self-sealing of cement-bound building materials.