Effects of Polycarboxylate Ethers with Different Charge Densities on the Time-Dependent Rheological Property of Cement Slurry

Effects of polycarboxylate ethers (PCEs) with different charge densities on the time-dependent rheological property (yield stress) were systematically investigated by correlating the charge density of PCE with its adsorption behavior, dispersion capability (including the dispersion rate and dispersion extent), and packing density, fluidity, and hydration kinetics of the cement slurry. Results show that with the increase of charge density, the adsorption rate of PCE increases, which is attributed to the increase of affinity between PCE and cement particles. Based on this, the dispersion rate of PCE is effectively enhanced by increasing its density charge, which results in a faster packing rate, consequently lowering the decrease of the time-dependent yield stress of cement slurry and increasing the fluidity loss over time. Noticeably, the stronger affinity raised from higher charge density leaves fewer PCEs in the solution of cement slurry, which is remarkable at high dosage, and thus leading to a faster fluidity loss or time-dependent yield stress increase. This will also lead to slower hydration kinetics with the same PCE content. These findings can provide guidance for the design of PCE structures in regulating the workability of concrete.