Keywords
meso-scale; salt frost damage, water transport, FTCs, sodium chloride
Abstract
Salt frost damage of concrete is an important durability issue to concern since it can threaten to the structural safety. The mechanical properties of concrete could be degraded while the corrosion of steel bar can be initiated because of the penetration of chloride ion. After freeze-thaw cycles (FTCs), due to the increase of connectivity, the water transport property could be changed which is the main reason of steel corrosion. However, because of the non-uniform salt frost damage of concrete in depth direction, how the water transport in mortar influenced by the combined effects of sodium chloride and FTCs is still not clear. In this study, the water transport behavior of meso-scale salt frost damaged mortar samples was studied. Different water-to-cement ratios (0.3 and 0.7) and salt solution concentrations (DI water, 5% NaCl, 15% NaCl and 20% NaCl) were adopted for comparisons. In total, 30 FTCs were tested. After three-point bending test, the central part was removed and the remaining specimens (30×30×5 mm) were immersed into deionized water for evaluation of the transport property. The results show that the porosity increased clearly with FTCs for pure frost damage case, whereas different tendency was observed in salt frost damage cases. Finally, the relationship between the mechanical degradation and water transport property change is discussed, which can promote the understanding of salt frost damage mechanism.
Response to reviewer's comments
Meso-scale Study of Water Transport in Mortar Influenced by Sodium Chloride and Freeze-thaw Cycles
Salt frost damage of concrete is an important durability issue to concern since it can threaten to the structural safety. The mechanical properties of concrete could be degraded while the corrosion of steel bar can be initiated because of the penetration of chloride ion. After freeze-thaw cycles (FTCs), due to the increase of connectivity, the water transport property could be changed which is the main reason of steel corrosion. However, because of the non-uniform salt frost damage of concrete in depth direction, how the water transport in mortar influenced by the combined effects of sodium chloride and FTCs is still not clear. In this study, the water transport behavior of meso-scale salt frost damaged mortar samples was studied. Different water-to-cement ratios (0.3 and 0.7) and salt solution concentrations (DI water, 5% NaCl, 15% NaCl and 20% NaCl) were adopted for comparisons. In total, 30 FTCs were tested. After three-point bending test, the central part was removed and the remaining specimens (30×30×5 mm) were immersed into deionized water for evaluation of the transport property. The results show that the porosity increased clearly with FTCs for pure frost damage case, whereas different tendency was observed in salt frost damage cases. Finally, the relationship between the mechanical degradation and water transport property change is discussed, which can promote the understanding of salt frost damage mechanism.
