柠檬酸改性低分子量减水剂的合成、性能及机理

Synthesis,Properties and Mechanism of Citric Acid Modified Low-molecular-weight Superplasticizers

以柠檬酸(CA)和聚乙二醇聚丙二醇单甲醚(MPEPPG)为主要反应原料,通过酯化反应合成一种柠檬酸改性低分子量减水剂(LMWS)。通过红外光谱、核磁氢谱和凝胶色谱测试获得合成减水剂的结构参数信息。同时通过动态光散射(DLS)、水泥净浆Zeta电位、减水剂对水泥的吸附性能、水泥净浆凝结时间、水泥水化热、水泥净浆塑性粘度、水泥净浆流动度及混凝土性能等研究对比了相同酸醚比(n(CA)∶n(MPEPPG)=1∶1)时不同分子量LMWS的综合性能。结果表明:相同掺量条件下,分子量适中的LMWS-3显著降低水泥净浆的塑性粘度并延缓水泥的水化进程,具有优异的初始分散和分散保持性能。

Citric acid modified low-molecular-weight superplasticizers(LMWS)was prepared by esterification reaction with citric acid(CA)and methoxy polyethylene polypropylene glycols(MPEPPG)as main raw materials.The superplasticizers were tested by Fourier transform infrared spectrometer(FTIR),1H nuclear magnetic resonance(1H NMR)and gel permeation chromatography(GPC)to obtain structural parameters.Meanwhile,the comprehensive performance of LMWS with the same acid-ether ratio(n(CA)∶n(MPEPPG)=1∶1)and different molecular weight was compared by the dynamic light scattering(DLS),Zeta potential of cement paste,the adsorption performance of superplasticizers on cement,setting time of cement paste,cement hydration heat,plastic viscosity,fluidity of cement paste and concrete performance.The results showed that under the condition of same dosage,LMWS-3 with moderate molecular weight significantly reduces the plastic viscosity of cement paste and delays the hydration process of cement,and also has excellent initial dispersion and dispersion retention performance.