关键词: 聚羧酸减水剂;分子结构设计;早强;保坍;水化产物

Abstract: According to the principle of molecular design,A new type of polycarboxylate (PC) superplasticizer with early strength and slump loss resistance was prepared by free-radical copolymerization,which selects Prenyl polyxyethylene ether (TPEG),N-Methylol acrylamide (N-MA) as co-monomers and mixed the fuctional macromolecules which contained functional groups of carboxyl (-COOH),hydroxyl (-OH).The result shows that the optimal PC superplasticizer can be obtained at n (TPEG) ∶ n (acrylic acid AA) ∶ n (N-AM) ∶ n (macromolecules) =1 ∶ 7∶ 4∶ 3,the reaction temperature is 60 ℃,the reaction time is 4-5 h,then water reducing rate is up to 32％,the initial slump of concrete can reach 220 mm,the 2 h slump remaines at 160 mm,1 day's ratio of compressive strength is 185％,and 3 day's is 177％.The molecular structure of PC superplasticizer is characterized by Fourier transform infrared spectroscopy and the molecular mass and distribution analysis is characterized by Gel permeation chromatography respectively.The FT-IR shows that the expected functional groups contain a large number of carboxyl,amide,ester and ether bonds in the PC superplasticizer,and the GPC displays that molecular weight distribution of PC are evenly,the weight-average molecular weight (Mw) is about 36000 and the number-average molecular weight (Mn) is about 20000.X-ray diffraction is used to characterize the hydration products of cement.Comparing the adding PC superplasticizer to cement and blank sample,PC superplasticizer can delay the process of hydration of silicate clinker minerals,but can promote the growth of ettringite,the transformation from AFt to AFm,which can improve hydration rate and the early strength.

Key words: polycarboxylate superplasticizer;principle of molecular design;early strength;slump loss resistance;hydration product