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Polycarboxylate Superplasticizers With Low Sensitivity to Clay via RAFT Polymerization

Yanan Chao,Xinde Tang,Fei Ma,Xinyan Wang,Ruixin Fu,Xuanjie Zheng,Zihao Tang,Laixue Pang,Yong Yang,Fuying Dong

Clay rapidly adsorbs polycarboxylate superplasticizers (PCEs), reducing effective dispersant concentration in cement slurries. In this work, using ethylene glycol monovinyl polyethylene glycol ether (EPEG) and acrylic acid (AA) as the main raw materials, three cationic functional PCEs (RPCEs: RPCE-A, RPCE-D, RPCE-S) with enhanced clay tolerance were prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization. These PCEs were characterized by FTIR, 1 H NMR, and GPC. The polydispersity index of RPCEs (1.24–1.27) indicated the character of living/controlled polymerization. Compared with the conventional PCEs, RPCEs can significantly enhance the fluidity of cement paste, and the fluidity retention can reach fine stability even when the clay occupies 0.5 wt.% of cement. X-ray diffraction and fluidity analysis show that, unlike the conventional PCEs, RPCEs can enter the clay layers through side-chain intercalation and ion exchange, resulting in an increase in layer spacing. This approach can open an avenue for broadening the application and increasing the adaptability of PCEs.