Synthesis And Performance Of Polycarboxylate Superplasticizers Via Water-soluble Azo Initiator

Polycarboxylate superplasticizer, which is one of the concrete additives, has became animportant direction for the development of high-performance concrete superplasticizersbecause of its advantages such as high water reducing ratio, well restraint of slump loss, lowmixing amount, programmable molecular structure, environmental protection and othercharacteristics. This paper introduces the action mechanism and synthesis methods ofpolycarboxylate superplasticizers and status of research and application of polycarboxylatesuperplasticizers and depth analysis of water soluble azo initiators advantage agent. Throughthe molecular design, carboxyl groups, sulfonic acid groups, and PEO side chains weresynthesized on molecular of polycarboxylate superplasticizers by radical copolymerization.In this paper, azobisisobutylamidine hydrochloride (AIBA·2HCl) as initiator inpolymerization of polyoxyethylene allyl ether (APEG) and maleic anhydride(MA)synthesized polycarboxylate superplasticizer(PC-1). Methyl alkenyl ethoxylates (TPEG), theactivity of acrylic acid (AA) and methacrylic sulfonate (MAS) synthesized polycarboxylatesuperplasticizer (PC-2).Through the discussion of factors determine the optimum polymerization prcessparameters of the synthesis of PC-1and PC-2: the monomer molar ratios of n(MA):n(APEG)=2.5:1, n(TPEG):n(AA):n (MAS)=1:3.5:0.4, initiator accounted the proportion of the totalmass of the monomer was3.0%and2.0%, the reaction temperature was70℃and65℃,reaction time5h, the reaction concentration was40%and the feeding methods of initiatorsolution and reactive monomer AA solution were dropping.Gel permeation chromatography and infrared spectrometry were used to determine thestructure of self-made polycarboxylate superplasticizers. The compatibility with different cement, the adsorption capacity of cement, the mortar water reduction, the compressivestrength of concrete, the slump retention and other tests to determine the self-madesuperplasticizers performance. The results showed that when mixing self-madesuperplasticizers with concrete, the slump retaining ability and the performance of latecompressive strength of concrete enhancement etc. are better than the similar polycarboxylatesuperplasticizers which was initiated by ammonium persulfate(APS).