Preparation and Properties of Polycarboxylate Superplasticizer Based on Chain Transfer Agents with Various Structures

Polycarboxylate superplasticizer (PCE) is a common admixture in high performance concrete. In the design of PCE molecules, it is necessary to ensure that the molecular weight of the polymer is moderate and the acid-ether ratio is appropriate to improve the dispersion effect. Chain transfer agent is usually added in the synthesis of PCE to adjust the molecular weight and distribution of PCE. In this study, three sulfhydryl chain transfer agents with different electron-withdrawing groups or electron-donating groups were synthesized by nucleophilic addition reaction based on sodium hydrosulfide method. Then, three kinds of PCE containing sulfhydryl chain transfer agent were prepared and compared with commercial beta-mercaptopropionic acid superplasticizers. The yield stress and plastic viscosity of cement paste samples prepared by PCE-A and PCE-M were close to those prepared by PCE-P. PCE-M and PCE-A prepared by chain transfer agent with electron-withdrawing group had higher dispersion and retention capacity than PCE-P, and had more obvious delay of cement hydration and lower hydration accumulated heat. Therefore, the optimization of molecular structure of chain transfer agent is helpful to improve the properties of concrete superplasticizer. Three PCEs using as-prepared sulfhydryl chain transfer agents with different electron-withdrawing or electron-withdrawing groups were Prepared. The dispersal capacity and dispersal retention capacity of PCE-M and PCE-A were higher than PCE-P, thus causing more significant cement hydration delay and less accumulated heat by hydration. Compared to the PCE prepared using commercial beta-MPA, PCEs synthesized using MMA and MAA both show improved performance. image