梳型长短侧链聚羧酸减水剂对水泥早期水化行为的影响及作用机理

Early Hydration Behavior of Comb-Like Polycarboxylate Superplasticizers with Long and Short Side Chain and Its Mechanism

调节异戊烯醇聚氧乙烯醚(TPEG)的聚合度及与丙烯酸(AA)的摩尔比,以过硫酸铵(APS)为引发剂、甲基丙烯磺酸钠(MAS)为链转移剂,通过水溶液自由聚合法合成了长侧链聚羧酸(LPCE)、长短侧链聚羧酸(LSPCEs)和短侧链聚羧酸(SPCE)3类梳型聚羧酸减水剂(PCEs)。研究了长短侧链比例对水泥早期水化行为的影响,进一步通过PCEs水溶液聚集形态、吸附性能和引气性能等探讨了长短侧链比例对水泥水化行为影响的作用机理。结果表明,SPCE有利于延缓水泥的早期水化,使水化诱导期延长,这是由于SPCE较LSPCEs和LPCE,在水泥颗粒表面的吸附量更大、吸附层厚度更高所致。加入水泥后,随着短侧链比例的增大,PCEs水溶液的起泡高度有增加趋势,而LPCE水溶液的黏度较大,稳泡性能较LSPCEs和SPCE好。

Three kinds of comb-like polycarboxylate superplasticizers(PCEs):polycarboxylate superplasticizer with long side chain(LPCE),polycarboxylate superplasticizers with long and short side chain(LSPCEs)and polycarboxylate superplasticizer with short side chain(SPCE)were synthesized by free polymerization in aqueous solution using ammonium persulfate(APS)as initiator and sodium methacrylate sulfonate(MAS)as chain transfer agent.The effect of the ratio of long and short side chains on the early hydration behavior of cement was studied,and the mechanism was further discussed through the research of the aggregation morphology,adsorption performance and air entrainment performance of PCEs aqueous solution.The results show that SPCE is helpful to delay the early hydration of cement and increase the hydration induction period.This is because SPCE contains more carboxylic acid radicals than LSPCEs and LPCE.The adsorption amount of SPCE on the surface of cement particles is the largest and the thickness of the adsorption layer is the highest.After adding cement,the foaming height of PCEs aqueous solution tends to increase with the increase of short side chain ratio,but the viscosity of LPCE aqueous solution is higher,and the foam stabilization performance is better than that of LSPCEs and SPCE.