The hygric properties of cement mortar with salt spray deposition

Many buildings along the coast are exposed to the salt spray climate, but the hygric behavior of porous building materials under the influence of salt crystallization are unclear. In this study, an accelerated salt spray test was conducted on cement mortar. For samples with different salt spray cycles, chloride ion content was measured and saturated moisture content (w(sat)), open porosity (p(o)) and apparent density (rho(b)) were obtained by a vacuum saturation test, while capillary absorption coefficient (A(cap)) and capillary moisture content (w(cap)) were determined from capillary absorption tests using innovative methods. Additionally, the pore characteristics and micromorphology of the samples were examined and analyzed using a mercury intrusion porosimeter (MIP) and a scanning electron microscope (SEM). The results indicate that a large amount of deposited salt crystals mainly clogs pores with a diameter of 0.02 to 0.12 microns, resulting in a 18.7 % decrease in p(o) as well as a 30 % decrease in A(cap) and a 17.4 % decrease in w(cap) subjected to 35 salt spray cycles. This finding supports a deeper understanding of fluid moisture absorption and transfer in building envelope materials in coastal areas.