| Polycarboxylic water-reducing agent is an important kind of chemical admixtures in concrete. The comb-type polycarboxylic water-reducing agent can disperse cement particles evenly with low dosage and low slump loss. Owing to poor performance and stability of macromonomer and polycarboxylic water-reducing agent products, it's nessary to do some related research. Firstly, detecting methods and conditions of carboxylic compounds'unsaturated double bond were studied. Then, the optimized and synthetic conditions of poly(ethylene glycol) methyl ether methacrylate were studied. Thirdly, synthetic formulation, reaction conditions and the properties of quaternary polycarboxylic water-reducing agent PC-1 and PC-2 were studied. Finally, mixing polycarboxylic water-reducing agent with various surfactants was studied. The main contents and results are as follows:1. Three different methods of detecting carboxylic compounds'unsaturated double bond were studied. Finally tribromide method was treated as the best one, and the detecting conditions were also studied. Such as solvent, reaction temperature, reaction time. At last, the standard method was established for detecting unsaturated double bond of metharcylic acid. Recovery rate of MAA reached 99.22% under the optimal conditions which were 45oC, 30 min, deionized water(solvent).2. MPEGMA was synthesized from MAA and MPEG under the influence of p-TSA and inhibitor T. The optimized reaction conditions, which were 140oC, 6 wt% of inhibitor T, 2 wt% p-TSA, n(MAA):n(MPEG)= 3:1(mol:mol), 8 h, 30 wt% of benzene, were obtained via single factor experiments. Esterification rate reached 93.54% under the condition above.3. Quaternary polycarboxylic water-reducing agent PC-1 was synthesized from poly(ethylene glycol) methyl ether methacrylate(MPEGMA), acrylic acid(AA), methyl acrylate(MA), and sodium methylacrylsulfonate(SMS). Ammonium persulfate(APS) was used for the radical aqueous polymerization as the initiator. The optimized reaction conditions, which are n(SMS): n(MPEGMA): n(MA): n(AA) = 17: 8: 6: 69, mol:mol; 85oC, 0.7 wt% of APS, were obtained via single factor experiment and orthogonal test. The initial cement paste fluidity reached 322mm by using 0.6 wt% of the product in the cement paste (W/C=0.3). PC-1 had stable and reliable performance and initial cement paste fluidity only decreased 2.4% after 4 month. However, the retention characteristics was not so good as dispersibility and stability. The cement paste fluidity decreased 11.3% after 2 h. In addition, the water-reducing agent has a good performance when its number-average molecular weight distributed from 50000 to 55000.4. In order to improve the retention characteristics of polycarboxylic water-reducing agent, quaternary polycarboxylic water-reducing agent PC-2 was synthesized from OXAC-608 macromonomer which replaced MPEGMA. The optimized reaction conditions, which are n(SMS): n(OXAC-608): n(MA): n(AA) = 20: 8: 8: 64, mol:mol; 85oC, 1.1 wt% of APS, were obtained via single factor experiment and orthogonal test. The initial cement paste fluidity reached 320 mm by using 0.6 wt% of the product in the cement paste (W/C=0.3). PC-2 also had stable and reliable performance and initial cement paste fluidity only decreased 1.0% after 4 month, 1.4% more was researved comparing to PC-1. The retention characteristics improved largely and cement paste fluidity only decreased 6.2% after 2 h, 5.1% was researved comparing to PC-1. The results were obtained via the macromonomer replacing. Furthermore, PC-1 and PC-2 were compared with four commercial products and the disperibility was both better than others.5. Aiming at utilizing the synergy effect of surfactant to enhance the retention characteristics and product efficiency with lower cost, some binary surfactant systems were tested by mixing the polycarboxylic water-reducing agent PC-1 with various commercial surfactants, respectively.The best result could be obtained by adding 10 wt% Tween-80, which can increase the fluidity of the cement paste up to 11%.
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