Mechanism of long-term capillary water uptake in cementitious materials

Abstract

Capillary imbibition or water uptake tests are practical and they satisfactorily describe the performance of cementitious materials. Most of these tests are performed for a short period (<1 week), however, additional water uptake has been documented after the water front has covered the total height of samples. This process occurs at a very low rate and it could provide further information about the pore structure. We investigated long-term capillary imbibition in mortar and concrete with and without supplementary cementitious materials. This paper reports our results and results from literature, and proposes a phenomenological description of the process. The trends observed from long-term tests are consistent across different water to cementitious material ratios, binder types, fine and coarse aggregates, curing ages, and conditioning regimes. Long-term measurements reveal primary and secondary periods of capillary imbibition that are well described by a bi-linear relationship with the fourth root of time.