2017 Volume 71 Issue 1 Pages 56-61
Chloride ion causes the rust of ion rebar, and the rust results in the degradation of the concrete. Therefore the immobilization of chloride ions is necessary for the concrete which is used in salt-damage environments, and the AFm phase generation is important for the immobilization. This paper investigated the Afm phase generation in cementitious materials which are made of low heat Portland cement（LHC）, moderate-heat Portland cement（MPC）, an ettringite-type expansive additives（CSA）, and CaO・2Al2O3（CA2）. In the LHC-CSA-CA2 type material, the required amount of CA2 for the AFm phase generation was 6mass％. On the other hand, in the MPC-CSA-CA2 type material, the required amount was 4.5mass％. This difference between the required amounts relates to the amount of reacted SO3 and the amount of reacted Al2O3. When the molar ratio of reacted SO3 to reacted Al2O3 was less than1, which corresponds to monosulfate, the AFm phases were generated. The resistivity to calcium elution of the MPC-CSA-CA2 type material was enhanced by the carbonation of the material’s surface. This carbonation generated the calcite coat on the material and it is supposed that this coat decreases the influence of chloride ions on the material. In the non-carbonated inner part of the material, AFm phases still remained.
