2017 Volume 71 Issue 1 Pages 191-196
In Japan, salt attack damages reinforced concrete structures particulary from ocean supplied water and from snow melting agent which one of the major deteriorating factor of concrete structures. Therefore it is necessary to improve the resistance of chloride ion diffusion of concrete to achieve sustainable society. This paper investigates the chloride ion diffusion behavior in blast furnace slag cement with CaO・2Al2O3. Since the use of CaO・2Al2O3, the penetration depth of chloride ion in the mortar was found to reduce, the mechanism had been evaluated through the hydration analysis. The amount of hydrocalumite was increased as a function of CaO・2Al2O3 dosage. This indicates that the amount of immobilizible chloride ion as Friedel’s salt is increased according with CaO・2Al2O3 dosage. In addition to that, the reduction of both total pore volume and capillary pore volume after salt water immersion became remarkable by adding more CaO・2Al2O3. By this change, blast furnace slag cement with CaO・2Al2O3 becomes more dense hardened mortar than that without CaO・2Al2O3 after salt water immersion. From these results, it was confirmed that the resistance of chloride ion diffusion in blast furnace slag cement is improved by the use of CaO・2Al2O3 in the view point of both chemically and physically, that is by immobilization of chloride ion as Friedel’s salt and densification of pore structure.
