Effect of Freeze-Thaw Cycles on Chloride Transportation in Concrete: Prediction Model and Experiment

This research aims to investigate the effect of frost damage on chloride transportation mechanism in ordinary and fiber concrete with both theoretical and experimental methods. The proposed theoretical model takes into account the varying damage levels caused by concrete cover depth and freeze-thaw cycles, which are the two primary parameters affecting the expression of the chloride diffusion coefficient. In the experiment, three types of concrete were prepared: ordinary Portland concrete (OPC), polypropylene fiber concrete (PFC), and steel fiber concrete (SFC). These were then immersed in NaCl solution for 120 days after undergoing 10, 25, and 50 freeze-thaw cycles. The damage coefficient of the tested concrete was determined by measuring the dynamic elastic modulus. The results indicated that the relative dynamic elasticity modulus of the specimens decreased with each freeze-thaw cycle, and the chloride diffusion coefficient of the specimens increased as the degree of frost degradation increased. Samples containing steel and polypropylene fibers exhibited greater resistance to cyclic water freezing compared to the controlled concrete without fibers. A model has been also developed that takes into account the damage caused by freezing-thawing cycles and the depth of the concrete, which can predict variations in free chloride concentration at different depths. The calculated values were in good agreement with the test results for depths between 10 to 30 mm. This new damage-induced diffusion model can help fill the gap in research on the effects of freeze-thaw cycles on chloride diffusion. © 2023 Tech Science Press. All rights reserved.