Effect of water reducing agent on bleeding
According to the mechanism of superplasticizer, polar molecules are adsorbed around the cement particles, which make the particles repel each other, reduce flocculation, release the water wrapped by the cement particles, meanwhile, make the adsorbed water layer on the surface of the cement particles thin, and the required wetting water amount is greatly reduced. Based on this mechanism, water reducing agent will increase the free water amount of bleeding in fresh concrete and make the bleeding increase. However, on the other hand, due to the water reducing effect of water reducing agent, the mixing water required for concrete with the same slump is greatly reduced, so that the free water in concrete can be secreted to reduce water. The final bleeding situation depends on which role plays the leading role.
The adaptability of admixtures and cement also affects the bleeding of concrete. At present, there is no recognized research achievement on the adaptability mechanism.