The Application of Polycarboxylate Superplasticizer/PCE in Gypsum

When the dosage of the polycarboxylate superplasticizer/PCE high-efficiency water reducer is 0.2% to 0.3% of the cementitious material's mass, the water reduction rate can reach 25% to 45%. It is generally believed that the polycarboxylate superplasticizer/PCE high-efficiency water reducer has a comb-like structure. It adsorbs on the cement particles or the cement hydration products, generating a three-dimensional steric hindrance effect, which disperses and maintains the dispersion of the cement. The research on the adsorption characteristics of the water reducer on the surface of gypsum particles and the adsorption-dispersion mechanism has shown that the polycarboxylate-based superplasticizer PCE high-efficiency water reducer has a comb-like adsorption, with a relatively small adsorption amount on the gypsum surface and a weak electrostatic repulsion effect. Its dispersing effect mainly comes from the spatial steric hindrance effect of the adsorption layer. The dispersion effect produced by the spatial steric hindrance effect is less affected by the gypsum hydration process, thus having good dispersion stability.

The polycarboxylate-based superplasticizer PCE high-efficiency water reducer has excellent dispersion ability. Even at a small dosage, it can significantly improve the fluidity of gypsum. With the increase in dosage, the gypsum fluidity increases significantly. The polycarboxylate-based high-efficiency water reducer has a strong retardation effect. With the increase in dosage, the setting time increases significantly. The strong retardation effect of the polycarboxylate-based superplasticizer PCE high-efficiency water reducer, under the same water-gypsum ratio, may cause the gypsum crystals to deform and the gypsum body to become loose when the dosage increases, resulting in a decrease in the flexural and compressive strength of the gypsum with the increase in dosage.

The polycarboxylate ether superplasticizer PCE water reducer has a retardation effect on gypsum and reduces the strength of gypsum. Under the same dosage, adding cement and calcium oxide to gypsum can both increase the fluidity of gypsum. Due to the reduction of the water-gypsum ratio, the density of gypsum increases and its strength also increases. At the same time, due to the reinforcing effect of the cement hydration products on gypsum, the flexural and compressive strength of gypsum increase. With the increase in the dosage of cement and calcium oxide, the fluidity of gypsum increases, and an appropriate amount of cement can significantly increase the strength of gypsum.

When using the polycarboxylate ether superplasticizer PCE water reducer in gypsum, adding an appropriate amount of cement not only increases the strength of gypsum but also can obtain a large fluidity, and has a smaller impact on the setting time of gypsum.