羟丙基纤维素改性聚羧酸减水剂的合成及性能研究

Synthesis of polycarboxylate type superplasticizer modified by hydroxypropyl cellulose

以马来酸酐改性羟丙基甲基纤维素(MAHPMC)、丙烯酸及甲基烯丙基聚氧乙烯醚(SPEG2400)为单体,以双氧水-L-抗坏血酸(ASA)氧化还原体系为引发剂,采用免加热低温水溶液共聚法合成羟丙基甲基纤维素改性聚羧酸减水剂。试验结果表明:改性聚醚减水剂PES03,2 h内水泥净浆流动度基本无损失,减水率达30.9%,初凝和终凝时间都延长,增强效果明显。水泥水化热、X射线衍射(XRD)及电子扫描电镜(SEM)试验表明改性聚醚减水剂对水泥水化产物C-S-H、CH及AFt形成有一定延迟作用,改性聚醚减水剂从而表现出明显缓凝及保坍特性。

A modified polyether-type superplastizer （PES）was directly polymerized using MAPMC, acrylic acid （AA）and methyl ally polyoxyethylenether（SPEG2400 ）, with H202-Ascorbic acid as initiator with low temperature in aqueous media.The results showed that the water-reducing ratio PES03 was 30.9%, the fluidity of cement paste almost remained constant within 2 h,the setting time of cement on ini- tial and final was prolonged,the enhancement of cement was significant.The experiments of cement hydration heat,X-ray diffraction （XRD）and scanning electron microscopy （SEM）showed that the modified polyether superplasticizer remarkably affects the formation of crystalline ettringite （ AFt ）, portlandite （ Ca （ OH ） 2 ） and calcium silicate hydrate （ C-S-H ） gel in cement pastes, so the cement of modi- fied polyether superplasticizer showed the characteristics on retarding and keeping slump significantly.