β-环糊精侧链对聚羧酸减水剂抑制蒙脱土的影响

Effect of β-cyclodextrin pendant on dispersion robustness of polycarboxylate superplasticizers toward montmorillonite

采用水泥净浆和混凝土试验,详细研究了β-环糊精侧链对聚羧酸减水剂抑制蒙脱土负效应的影响。试验表明,与仅含有聚氧乙烯侧链的传统聚羧酸减水剂相比,蒙脱土对掺加含有β-环糊精侧链的聚羧酸减水剂水泥净浆流动度的负作用影响明显减弱;蒙脱土(1.0%,以砂质量计)存在时,为获得与无蒙脱土时相同的混凝土坍落度,β-环糊精类聚羧酸减水剂的掺量增幅减小,掺加β-环糊精类聚羧酸减水剂的混凝土抗压强度下降幅度减小。结合吸附试验分析,β-环糊精类聚羧酸减水剂抑制蒙脱土负效应能力的增强应归功于其侧链中的β-环糊精基团,β-环糊精基团具有中空筒状的刚性结构,其显著的空间位阻效应将阻止蒙脱土颗粒继续吸附其他β-环糊精类聚羧酸分子,进而提高聚羧酸减水剂抑制蒙脱土负效应的能力。

The effect of fl-cyclodextrin （β-CD） pendant on the dispersion robustness of polycarboxylate superplasticizers （PCEs） toward montmorillonite was studied via cement paste test and concrete experiment. Compared with conventional PCEs only with PEO chains, the negative effect of montmorillonite on the spread flow of cement paste containing PCEs with β-CD as pendants was weakened. When montmorillonite （1.0%, by mass of sand） was present, the dosage increment of PCEs with β-CD pendants to achieve the same spread flow of concrete as that in the absence of montmorillonite was decreased, the compressive strength decrement of concrete containing PCEs with β-CD pendants became reduced. These results demonstrated that PCEs with β-CD as pendants displayed enhanced robustness toward montmorillonite, which was attributed to β-CD pendant groups based on adsorption measurement. Due to the steric hindrance instigated from its rigid structure of hollow truncated cone, β-CD pendants would decrease the adsorption amount of PCEs on clay by hindering the sorption ofpolycarboxylate polymers on the surfaces of montmorillonite, leading to enhanced clay tolerance.