THE CHLORIDE ION PENETRABILITY IN RECYCLED AGGREGATE CONCRETE WITH MINERAL ADMIXTURES

摘要

The corrosion of steel bar caused by the chloride ions eroding into the concrete is the main reason of durability descent and fracture of concrete structure. The resistance of chloride ion penetration of recycled aggregate concrete is directly related to the safety and durability of the recycled aggregate concrete structure. In this paper, the chloride ions penetrability in the recycled aggregate concrete with mineral admixtures was tested by ASTM C1202. SEM observations reveal that recycled aggregate-cement interfacial transition zone(ITZ) and cement matrix of the recycled aggregate concrete consist mainly of dense hydrates. The SEM photos show that minimal admixtures,such as fly ash, granulated blast-furnace slag and so on, have involved in the second hydration reaction of cement or embedded in the hydrate products acted as filled materials, which can effectively improve the pore structure of ITZ and cement matrix of the recycled aggregate concrete and make the recycled aggregate concrete much denser. The testing results indicate that the resistance of chloride ion penetration of recycled aggregate concrete has been intensified with the growth of strength grade and curing age of recycled aggregate concrete and mineral admixtures can effectively enhance the resistance of chloride ion penetration of recycled aggregate concrete. The resistance of chloride ions penetration of recycled aggregate concrete with mineral admixtures can meet the engineering code.