Water transfer in building materials over capillary saturation during freezing

• Published in: Cold regions science and technology 2024-06, Vol.222, p.104199, Article 104199
• Main Authors: Fukui, Kazuma, Takada, Satoru
• Format: Article
• Language: English
• Subjects: Capillary saturation; Frost damage; Gamma-ray attenuation; Hygrothermal modeling; Porous building material; Water transfer
• ISSN: 0165-232X; 1872-7441
• DOI: 10.1016/j.coldregions.2024.104199

The risk of frost damage to building materials is strongly dependent on the water content, particularly when the water content is high. Therefore, to understand the moisture behavior of materials with high water content is essential to predict the frost damage risks of buildings. While little liquid water transfer takes place over the capillary saturation under unfrozen conditions, the pressure drop of the unfrozen water contained in the frozen domain (cryosuction) may be a strong driving force for water transfer during the freezing processes. Therefore, in this study, we investigated water transfer in a building material over capillary saturation during freezing through a one-dimensional freezing experiment using the gamma-ray attenuation method and hygrothermal simulations. In the experiment, an aerated concrete specimen, with a water content greater than the capillary saturation, was subjected to a temperature gradient by cooling the specimen bottom to the freezing temperature. The results show that significant water transfer occurred even in the capillary-saturated material during freezing and thawing. Water moved to the cold side in the material and the most significant water accumulation was observed at a position where the temperature was close to 0 °C. The hygrothermal simulation, including the freezing processes, confirmed that cryosuction was a dominant driving force of water movement and accumulation in the material compared with other driving forces, such as gravity and temperature gradient. Moreover, mechanism of the water accumulation at a position where the temperature was close to 0 °C was discussed from the perspective of water chemical potential distribution and water conductivity of the material. The findings of this study will help develop a more reliable model for evaluating moisture damage risks by considering the hygrothermal behaviors of building envelopes. •Investigated water transfer in porous building material during freezing.•Conducted a one-dimensional freezing experiment and hygrothermal simulation.•Cryosuction causes significant water movement and accumulation in the material.•Water content can increase even over the capillary saturation due to the freezing.