Effect of application time of water-based curing compound on strength, hardness, sorptivity and porosity of blending concretesud

摘要

This paper describes the effectiveness of water-based curing compound (WBCC) applied to concrete surface at different elapsed time from casting on the various properties of OPC, silica fume (SF) and fly ash (FA) concrete. It also signifies the importance of utilizing moist curing prior to applying WBCC .Four series of OPC, OPC/SF and OPC/FA cylindrical concrete specimens made with a constant water-binder ratio of 0.50 were prepared. For the first series, the casting surfaces were sprayed with WBCC after various elapsed periods from casting, 1, 2, 3, 4, 24 hrs, while, for the second series, the casting surfaces were pre-cured with water for 1, 3 and 7 days prior to the application of WBCC. The third and fourth series of samples were exposed to air and water curing regimes, respectively, until the age of testing (28 days). Various test techniques, namely strength, hardness, capillary absorption and porosity, were applied on the four series of samples to assess their mechanical and durability related properties. It was found that the efficiency of WBCC is significantly dependent on the time of its application, used blending material, period of pre-water curing specified prior to its application and considered property of concrete. Increasing the time of application of WBCC from casting can lead to diminishing the possible positive effect of using such regime of curing. The effects of WBCC's application time and period of pre-water curing on durability related properties (sorptivity and porosity) of blending concretes were found to be much greater than their effects on the mechanical (strength and hardness) characteristics.ud