Molecular mechanism design of polycarboxylic acid water reducer
Polycarboxylic acid high-performance water reducing agent can reduce bleeding in different ways. First of all, polycarboxylic acid superplasticizer reduces water consumption under the premise of ensuring the workability of cement-based materials. When the water consumption of the mixture is reduced, bleeding will be significantly reduced. Secondly, polycarboxylic acid superplasticizer has excellent dispersion effect, can fully disperse cement particles into the water, prevent the settlement of larger particles, so as to reduce bleeding. Third, polycarboxylic acid molecules are adsorbed on the surface of cement particles, so that cement particles repel each other, reduce the effective particle size of cement particles flocculated in a group, delay the sedimentation rate, reduce bleeding water. Another advantage is that the molecules of polycarboxylic acid superplasticizer are highly customizable. When the molecular weight is small, the dispersion will increase and bleeding will decrease slightly, but at the same time, the loss of concrete fluidity should also be considered. Similar to the influence of molecular weight on bleeding, the main chain adsorption group content, graft chain density, branch chain length and other factors in polycarboxylic acid molecule affect the bleeding of concrete.
Post time: May-18-2022