Water transport in foam concrete: visualisation and numerical modelling

Abstract

Most problems concerning the durability and functional degradation of foam concrete are intimately related to water transfer. The water transfer behaviour in foam concrete under capillary absorption and full submersion conditions is studied in this paper. To overcome the low resolution between water and cement paste in in-situ X-ray computed tomography (XCT) tests, caesium chloride (CsCl; 6 wt%) was used as a contrast-enhancement agent. The dynamic changes to the wetting head and water distribution in foam concrete were successfully visualised in two and three dimensions. The multiscale pore structure of foam concrete was quantitatively characterised by a combination of mercury intrusion porosimetry (micropore <10 μm) and XCT (macropore >10 μm). The results show that the microporosity governs a large part of the capillary suction of water due to the high capillary force in these micropores. However, for macropores, they are partially connected and can hold water under pressure and simultaneously hinder capillary rise due to the blocking of the capillary network and prolonged transfer tortuosity. Finally, a numerical finite-volume model was used to simulate the dynamic water transfer process directly based on the XCT binary images. The modelling results agreed well with the experimental results.