Post Date:17,Mar,2025
1. The adaptability of polycarboxylate superplasticizer water reducer to cementitious materials
Polycarboxylate superplasticizer and fly ash also have adaptability issues. The first-grade ash has good adaptability, while the second and third-grade ash are not adaptable. At this time, even if the polycarboxylate dosage is increased, the effect is not obvious.
Often, when a certain type of cement or fly ash is not well adapted to admixtures, you are still not completely satisfied when you change to another admixture. In the end, you may have to replace the cementitious material, but some users who don't know the reason often suspect that the quality and performance of the admixture are not good, which is unfair.
2. The mud content of sand
When the mud content of sand is high, the water reduction rate of polycarboxylate superplasticizer will be significantly reduced. The use of naphthalene superplasticizer is often solved by increasing the dosage. The change of polycarboxylate superplasticizer when increasing the dosage is not obvious. In many cases, when the fluidity has not reached the requirement, the concrete has begun to bleed. At this time, adjusting the sand ratio or increasing the air content or adding thickener will not be very effective. The best way is to reduce the mud content.
3. The dosage of polycarboxylic acid water reducer
① The dosage is very sensitive when the water-binder ratio is small, and it shows a higher water reduction rate. When the water-binder ratio is large (generally >0.4), the water reduction rate and its changes are not so obvious. The reason may be related to the mechanism of action of polycarboxylic acid water reducer. Its dispersion and retention effect lies in the steric hindrance effect formed by the molecular structure. When the water-binder ratio is large, there are already enough water molecules in the cement dispersion system, so the steric hindrance of polycarboxylic acid molecules is naturally smaller.
② The dosage effect is more obvious when the amount of cementitious material is large, and it is worse when the total amount of cementitious material is small. Under the same conditions, when the total amount of cementitious material is <300kg/m3, the water reduction effect is less than the water reduction rate when it is >400kg/m3, and there will be a superposition effect when the water-binder ratio is large and the amount of cementitious material is small. This shows that the application of polycarboxylic acid water reducer also has its scope.
Post time: Mar-17-2025
