Experimental study of chloride diffusivity in unsaturated ordinary Portland cement mortar
Y. Zhang (TU Delft - Materials and Environment)
G. (Guang) YE (TU Delft - Materials and Environment)
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Abstract
Experiments are carried out to investigate the chloride diffusivity in partially saturated ordinary Portland cement mortars with water-to-cement (w/c) ratios of 0.4, 0.5 and 0.6. Based on resistivity measurement and Nernst-Einstein equation, the chloride diffusivities of cement mortars at various water saturations are estimated. The pore structures of cement pastes obtained from mercury intrusion porosimetry tests are analysed, which provide basic insight into the moisture distribution of non-saturated cement mortars. It is found that the chloride diffusivity is highly dependent on water saturation. The dependency is closely related to the pore size distribution and pore connectivity of the material. There exists a critical saturation level at which the pore solution becomes discontinuous and ionic diffusion is impossible. An increase of the w/c ratio results in a decrease of the critical saturation level.