Study On Preparation And Properties Of Poly (Maleic Anhydride-co-acrylamide) High Range Water-reducing Agent

With the development of the high performance concrete and commercial concrete, the requirement for concrete admixture becomes higher and higher. Polycarboxylate series high range water-reducing agents, which can provide concrete high fluidity, good retarding performance and low slump loss, have become more popular recently.We successfully synthesized maleic anhydride-co-acrylamine copolymer in the water solution by radical copolymerization. The factors of molecular weight such as the degree of neutralization, the dosage of initiator, the concentration of reagent and the reaction temperature, have been discussed. And the relationship between these factors and molecular weight has been concluded. The best process of maleic anhydride-co-acrylamine copolymer as the water-reducing agent has been designed.In order to improve the performance of the maleic anhydride-co-acrylamine copolymer water-reducing agent, the copolymer is monoesterified with the polyethylene glycols. The fluidity of the esterified copolymer has been increased 60%, and it has good retarding performance. The relationship between the factors such as the molecular weight of copolymer and PEG, the proportion of monomers and PEG, have been discussed. And the best process of monoesteried poly (maleic anhydride-co-acrylamine) water-reducing agent has been designed.The amine group is sulfomethylated to improve the performance of the copolymer. The sulfomethylated copolymer can increase the fluidity of cement paste 20%, and it has longer time retarding performance. The influence of the molecular weight of copolymer and the proportion of monomers on the property of sulfomethylated copolymer has been discussed. The best process of sulfomethylated poly (maleic anhydride-co-acrylamide) is also designed.By testing setting time and water reducing rate of water-reducing agent, we find that the water-reducing ratio of the monoesterified MA-AM is 20%, and the sulfomethylated MA-AM is 6.3%. They both have good retarding performance. Bymeasuring the temperature of the cement paste with the water-reducing agent, we discover that the water-reducing agent can retard the cement hydration. Under alkaline condition, the descreasing of esterified copolymer viscosity indicate the esterified copolymer is slow releasing. The effect of the complex superplasticizers and the single one is compared in this paper.By measuring the water-reducing rate in the mortar and the mortar strength, we conclude that the modified copolymer can reducing the water in the mortar as well as cement, and esterified copolymer can increase the strength of the mortar but the sulfomethylated copolymer decrease the strength because of the long time retarding performance.By measuring surface tension, adsorptive content and ζ potential of the superplasticizer solution, the mechanism was studied. The modified copolymer solution has lower surface tension than the unmodified one. By measuring adsorptive content, we find that the adsorptive content of FDN superplasticizer is higher than the modified copolymers, but their adsorptive shape on the surface of the cement particles is different. Measuring of ζ potential of cement particle indicated that higher ζ potential leads to better dispersibility for used superplasticizer. The ζ potential of modified copolymer is higher than the unmodified.