The developing law of pore structure and resistance to chloride ion permeability of concrete at negative temperatures

To further reveal the development law of concrete pore structure and chloride ion permeability resistance under negative temperatures curing; mercury injection; and RCM methods were used to test the 28d pore structure and chloride ion permeability of concrete. Different water-cement ratios and hydration degree of the cement paste of the corresponding concrete under -3 ℃ curing were tested and compared with that of the standard curing condition. Results show better pore structure and chloride ion permeability of concrete under standard curing condition than under negative temperature curing. With increased water-cement ratio employing standard curing condition, the pore structure of concrete deteriorated; resistance to chloride ion permeability weakened. However, under -3 ℃ curing, the pore structure and chloride ion resistance permeability of concrete showed an initial trend of optimization, but then degraded with further increase of water-cement ratio. To analyze the causes of this phenomenon, a computational model of freezing point for water in the pores with different apertures was established. The hydration behavior and development law of pore structure under negative temperature, and the influence mechanism of the chloride ion permeability of cement-based materials were analyzed by using the model. Copyright ©2020 Journal of Harbin Engineering University.