Study on the Effect of Main Chain Molecular Structure on Adsorption, Dispersion, and Hydration of Polycarboxylate Superplasticizers

Polycarboxylate ether (PCE) with different main chain structures was prepared by aqueous solution free radical polymerization using unsaturated acids containing sulfonic acid groups, acrylamide groups, and carboxyl groups and isoprenyl polyoxyethylene ether (IPEG). The molecular structure was characterized by infrared spectroscopy and gel chromatography, while adsorption, dispersion, and hydration properties were studied using a total organic carbon analyzer, rheometer, and isothermal microcalorimeter, respectively. The results show that the adsorption process of PCE on cement particles is spontaneous physical adsorption. The adsorption forces are mainly electrostatic interaction, and hydrogen bonding. The introduction of sulfonic acid groups and polycarboxylic acid groups reduces the initial adsorption amount of PCE but can accelerate the adsorption rate of PCE on cement and increase the adsorption amount at the adsorption equilibrium. The introduction of acrylamide groups in the PCE main chain is beneficial to the initial dispersion of PCE and can reduce the plastic viscosity of cement slurry. PCE can delay the hydration of cement. The introduction of acrylamide groups and dicarboxylic acid groups in the PCE main chain helps prolong the induction period of cement hydration, while the introduction of sulfonic acid groups is not conducive to its retarding effect.

Automated summary

Polycarboxylate ether (PCE) with different main chain structures was synthesized using unsaturated acids with sulfonic acid groups, acrylamide groups, and carboxyl groups, as well as isoprenyl polyoxyethylene ether (IPEG). The molecular structure was characterized, and the adsorption, dispersion, and hydration properties were investigated. The results showed that the adsorption of PCE on cement particles is a physical adsorption process driven by electrostatic interaction and hydrogen bonding. The introduction of sulfonic acid groups and polycarboxylic acid groups reduced the initial adsorption amount but enhanced the adsorption rate and equilibrium amount. The introduction of acrylamide groups improved dispersion and reduced the viscosity of cement slurry. PCE also delayed the hydration of cement, with acrylamide and dicarboxylic acid groups prolonging the induction period while sulfonic acid groups had no retardation effect.