Concrete using polycarboxylate superplasticizer, compared with concrete using traditional naphthalene series, aliphatic water reducer, bleeding will be lower in most cases, less cases will be higher bleeding.But once the use of polycarboxylate superplasticizer concrete excessive bleeding situation, it is often difficult to adjust up.
Polycarboxylate superplasticizer can reduce bleeding in different ways.First of all, polycarboxylate superplasticizer reduces water consumption on the premise of ensuring the workability of cement-based materials. When the water consumption of mixture is reduced, bleeding will significantly decrease.
Secondly, polycarboxylate superplasticizer has excellent dispersion effect, can fully disperse cement particles into the water, prevent the settlement of larger particles, thus reducing bleeding.
Thirdly, polycarboxylate superplasticizer molecules are adsorbed on the surface of cement particles, which makes the cement particles repel each other, reduces the effective cement particle size of flocculation in a mass, delays the settling rate, and reduces bleeding.
Another advantage is that the molecules of polycarboxylate superplasticizers are highly customizable.With small molecular weight, dispersion increases and bleeding decreases slightly, but the concrete fluidity loss should also be considered.Similar to the influence of molecular weight on bleeding, main chain adsorption group content, graft chain density, branch chain length and other factors in polycarboxylate superplasticizer molecules all have an influence on concrete bleeding.
