Experimental study on hygric properties of salt-contaminated red sandstone in coastal building envelope

• Published in: Case Studies in Construction Materials Vol. 22; p. e04447
• Main Authors: Zhang, Yu, Meng, Qinglin, Li, Chuanrui, Wang, Junsong
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.07.2025; Elsevier
• Subjects: Hygric properties; Mechanism of salt effect; Moisture storage; Moisture transfer; Porous building materials; Porous building materials; Mechanism of salt effect; Hygric properties; Moisture transfer; Moisture storage
• ISSN: 2214-5095; 2214-5095
• DOI: 10.1016/j.cscm.2025.e04447

Building envelopes in coastal areas are exposed to both the heat and humidity of inland regions and the corrosive effects of salt spray. Given that these structures are often composed of porous materials, understanding the hygrothermal properties of such materials under saline conditions is crucial. This study investigates the hygric properties of salt-free and salt-contaminated red sandstones through a comparative analysis. Equilibrium sorption and desorption test, vapor permeability test, capillary absorption test, and drying test were employed to determine hygric property parameters. Results reveal that salt has a limited effect on capillary absorption coefficient and drying flow rate. However, salt had a greater effect on the equilibrium moisture content, with a maximum increase of 428.52 % for hygroscopicity and 485.34 % for exothermicity. In addition, the effect of salt on vapor permeability coefficient was classified as inhibition and facilitation. In the low RH range (RH < 75 %), salt inhibited vapor transmission with a maximum inhibition of 80.95 %; in the high RH range (RH > 75 %), salt promoted vapor transmission with a maximum promotion of 292.75 %. Lastly, the mechanisms underlying the effect of salt on the hygric properties of porous materials are elucidated through a series of microscopic experiments, which was attributed to the properties of salt (hygroscopic deliquescence and weathering crystallization). Due to the difference of relative humidity, salt affected the moisture content, porosity, contact angle, surface tension and viscosity of red sandstone, thereby influencing the hygric properties of porous materials. The findings of this study can provide essential hygrothermal parameters for the development of coupled heat, moisture, and salt transport models. •Comprehensive hygric properties of salt-contaminated red sandstone were test.•Salt significantly affects sorption/desorption isotherm and vapor permeability coefficient.•The effect of salt on the capillary absorption coefficient and drying flow rate is limited.•The effect mechanism of salt on hygric properties of red sandstone is revealed.