Transport properties of surface layers from full-scale reinforced concrete member

The durability performance of concrete structure is intimately related to the mass transport properties for the surface layers of concrete members. However, due to several effects, such as segregation, jamming effect and so on, the quality of the surface layer for reinforced member might be obviously different from their core material and material prepared and cured in the laboratory (labcrete). This study aims at understanding the mass transport properties of surface layers from reinforced concrete member, and clarifying the differences among them and those for accompanied labcrete. Specimens prepared from both a full-scale reinforced beam and labcrete are subjected to experimental investigations on their gas permeability, capillary sorptivity, chloride diffusivity, and chloride migration coefficients. It is found that, for the same specimen, the gas permeability is approximately linear to capillary sorptivity. While the chloride diffusivity is smaller than the rapid migration coefficient. The durability potential of surface layers for the reinforced beam is inferior to that of the inner core material. While the latter is further obviously worse than that of labcrete. In engineering practice, special attention should be paid to ensure the quality of surface layer. When making quantification or prediction for the durability potential of concrete structure, it is more appropriate to use specimens from surface layers of field concrete members rather than those from labcrete.