减缩型聚羧酸系减水剂的合成及性能研究

为了减少混凝土因收缩开裂引起的混凝土结构耐久性问题,研制了一种减水率高、水泥适应性好的减缩型聚羧酸系减水剂。首先使用丙烯酸、新戊二醇和携水剂,在阻聚剂和催化剂作用下制备了一种酯类功能单体;然后将酯类功能单体与异戊烯醇聚氧乙烯醚、丙烯酸及一缩二丙二醇等单体,在氧化-还原复合引发剂和链转移剂作用下进行共聚,合成了减缩型聚羧酸系减水剂TX-938。合成样品的性能试验结果表明:TX-938在分散性能及保持能力上与标准型聚羧酸系减水剂TX-50H基本相同,且具有较好的水泥适应性;TX-938在掺量为2.5%时可以将溶液表面张力从72.3 mN/m降低至31.6 mN/m;掺2种聚羧酸系减水剂的水泥胶砂试件的28 d干燥收缩率分别较空白样降低了10.5%和29.1%,TX-938更能显著降低水泥胶砂的干燥收缩;掺2种聚羧系减水剂的混凝土初凝后72 h收缩率分别为452×10^-6和399×10^-6,掺TX-938的混凝土收缩率为掺TX-50H的88%,混凝土28 d掺TX-938收缩率仅为空白样的35.6%,比掺TX-50H降低1/2倍还多;TX-938的减水率达到29.4%,混凝土不同龄期强度也没有负面影响。

Synthesis and Performance of Shrinkage-reducing Polycarboxylate Superplasticizer

To solve the durability of structures caused by shrinkage and crack of concrete,we prepared an shrinkage-reducing polycarboxylate superplasticizer(PS)with high water-reducing rate and good cementitious compatibility. Firstly,an ester macromonomer was prepared by using acrylic acid,neopentyl glycol and water-carrying agent in as-sociation with polymerization inhibitor and catalyzer.Then,the shrinkage-reducing PS of TX-938 was synthesized by using the ester monomer,isoamyl alcohol polyoxyethylene ether,acrylic acid and dipropylene glycol with the com-bined effect of the oxidation-reduction initiator and chain-transferring agent.The performance that we tested shows that,as for cement dispersion property and adaptability,the shrinkage-reducing PS of TX-938 is almost equal to TX-50H,which is a kind of normal PS;moreover,TX-938 can significantly decrease the surface tension from 72.3 mN /m (without TX-938 )to 31.6 mN /m with the blending ratio of 2.5%;then,the drying shrinkage of mortar blended with TX-50H and TX-938 decreases by 10.5% and 29.1% respectively when compared with that of mortar without PS;72 hours after initial set ,the drying shrinkage of concrete is 452 ×10 -6 and 399 ×10 -6 respectively,in other words,the drying shrinkage of concrete with TX-938 was only 88% of that of concrete with TX-50H,and the 28d dr-ying shrinkage of concrete with TX-938 is only 35.6% of that of concrete without PS,less than 50% of that of con-crete with TX-50H;finally,the water-reducing rate of TX-938 is up to 29.4% and TX-938 has no negative effect on compressive strength of concrete at different ages.