The effect of pore structure on the pessimum effect of salt scaling: A perspective from cryogenic liquid transport and ice pressure

Salt scaling damage peaks at a specific salt concentration, known as the pessimum concentration. However, reported pessimum concentrations vary widely, lacking a theoretical explanation. The microstructure of concrete is an important characteristic influencing the freezing behavior of pore solution, which is often neglected in salt scaling studies. This study investigates the effect of concrete microstructure on the pessimum concentration by review, experiment, and modeling. The results show that the pessimum concentration increases from 3 % to 7 % as the water-binder ratio decreases from 0.4 to 0.2. An ice content and cryosuction model considering the role of salt and pore structure is developed to establish the relationship between cryogenic liquid transport and damage. The analysis reveals that the cryogenic permeability, as affected by ice formation in the pore system, plays a crucial role in determining the pessimum concentration. A decrease in porosity and critical pore diameter reduces the cryogenic permeability, resulting in lower liquid absorption at low concentrations, and increasing the pessimum concentration.