Preparation, Characterization, and Performance Evaluation of a New Type of Polycarboxylate Superplasticizer With Star‐Shaped Structure

ABSTRACT Star‐shaped monomer was synthesized from pentaerythritol, acrylic acid, and diallylamine by esterification reaction and Michael addition reaction. The star‐shaped polycarboxylate superplasticizer CPCE was prepared by free‐radical polymerization of ethylene glycol monovinyl polyoxyethylene ether with acrylic acid and star‐shaped monomer in a H 2 O 2 ‐Vc redox initiator system. Comb‐shaped polymer YPCE was also prepared for comparison. The synthesis parameters were optimized through cement slurry fluidity tests using the single‐factor experimental method, and molecular structures were characterized by FTIR, NMR, and GPC techniques. The dispersion mechanistic investigations were carried out by means of techniques such as the rheological properties, Zeta potential, total organic carbon adsorption, X‐ray photoelectron spectroscopy, scanning electron microscopy, and optical microscopy. The performance test results of CPCE and YPCE are as follows: mortar water reduction rate 28.9% versus 26.6%, slump of concrete 200 mm versus 155 mm, expansion of concrete 387.5 mm versus 360 mm, the concrete compressive strength 13.7 MPa versus 22.5 MPa (3‐day), 20.6 MPa versus 25.9 MPa (7‐day), and 27.4 MPa versus 30.4 MPa (28‐day), respectively, which imply that the CPCE has excellent dispersion, water reduction, and compression resistance properties. The hydrodynamic radii of CPCE and YPCE in pore solution are 32.7 and 21 nm, respectively. CPCE has a thicker adsorption layer than that of YPCE, 1.27 nm versus 0.56 nm, which may be attributed to the larger spatial site resistance of CPCE. Results of the mechanistic study show that the excellent water reduction and dispersion properties of CPCE are attributed to both the electrostatic repulsion effect and the steric hindrance effect.