聚羧酸减水剂酸醚比对其引气性能的影响

Effects of Polycarboxylate Polymers with Different Acid Ether Ratio on the Air Entraining Property

通过水溶液自由基聚合法合成了一系列不同酸醚比的聚羧酸减水剂,研究了不同酸醚比的聚羧酸减水剂对新拌水泥浆体含气量、流变性以及水泥砂浆分级气泡含量的影响.结果表明:随着酸醚比的增加,聚羧酸减水剂分散性能及引气性能显著增加,其中当丙烯酸与异戊烯醇聚氧乙烯醚(TPEG)单体摩尔比达到4∶1时,聚羧酸减水剂分散性能及引气性能均达到较大值,随着酸醚比的进一步增加,聚羧酸减水剂分散性能与引气性能呈下降趋势;随着酸醚比的增加,聚羧酸减水剂在水泥颗粒表面的吸附能力增加,使得水泥颗粒表面的聚羧酸分子浓度增加,降低了水泥颗粒-水的固-液界面能;聚羧酸减水剂能够显著改善砂浆气泡孔径分布,在引入大量中小气泡的同时降低大孔径气泡的占比,使得气泡孔径分布更加细小化;同时,随着聚羧酸减水剂主链中酸醚比的增加,引入的小气泡占比呈下降趋势,大孔占比呈上升趋势.

A series of polycarboxylate(PCE)polymers with different molar ratio between TPEG and acid ether have been synthesized through radical copolymerization.Effect of PCE with different acid ether ratio on the air entraining property and dispersing property of fresh cement paste was investigated,and effect of PCEs with different acid ether ratio on the graded bubble structure of cement mortar was also investigated.The results show that with the increase of acid ether ratio in the PCE molecule,the air entraining and dispersing property of PCE improves.When the molar ratio between acrylic acid and TPEG monomer is higher than 4∶1,the dispersing and air entraining property of PCE reaches a relatively higher value.However,further increase of acid ether ratio leads to the decrease of air entraining performance as well as dispersing capability.With the increased acid ether ratio,the adsorption capability of PCE onto the cement surface improves which results in the increased concentration of PCE on the cement particle surface and leads to the decreased interface energy between cement particles and liquid phase.The addition of PCE can significantly improve the bubble structure of cement mortar,which mainly entrains a large number of bubbles of small and medium sizes,and decreases the proportion of large-size bubbles.In this way,the bubble size tends to be smaller.With the increased acid ether ratio in PCE molecule,the proportion of small bubbles in cement mortar decreases,and the large bubbles in hardened cement mortar tends to increase.