2017 Volume 71 Issue 1 Pages 210-217
The air mass transport in concrete is influenced by moisture condition. Since the moisture condition of concrete change with drying condition, such as solar radiation, weather, and rain, it is important to clarify the relation between air mass transport and the moisture condition of concrete for concrete durability. On the other hand, it is obvious that the pore structure of hardened cement paste change with drying condition. And, the properties of hydration products also change with drying condition. However, the relation between air mass transport and pore structure, hydration products of hardened cement paste exposing various drying condition have not been clarified.
The purpose of this study is to estimate the relationship between air mass transport and pore structure, hydration products of hardened cement paste drying various relative humidity. The hardened cement paste, using blast furnace slag, was dried at RH 80％, 56％, 43％ and 22％. Experimental results show that the relation between Oxygen diffusion coefficient of hardened cement paste and open porosity is independent of materials and mix condition. On the other hand, oxygen diffusion coefficient using blast furnace slag is smaller than that using ordinary Portland cement in the case of high porosity. It is investigated in this point in detail. As the drying humidity decrease, the pore size distribution was coarsened. Particularly, porosity more than 10nm was increased. In addition, the specific surface area of hydration products was decreased. Furthermore, it is suggested that the influence by the change of macro pore structure dominant to air mass transport at high relative humidity, and the change effect of properties of hydration products dominant at low relative humidity.
