| Concrete water-reducing admixtures have become an indispensable part as the 5th composition in nowadays concrete industry, Among all kinds of superplasticizers for cement, Sodium salts of sulfonated naphthalene-formaldehyde condensates(PNS) are widely used in commercial concrete in china, Such agents are added to cement to maintain higher water-reducing ratio ,lower foaming ability and better applicability to various cement.The viscosity behavior of PNS in dilute water solution has been studied in detail by using a capillary viscometer. Here a characteristic polyelectrolyte effect has been observed in salt-free solution, the reduced viscosity increases greatly with decreasing concentration then it levers off at a higher PNS concentration in the presence of added salts, there is a linear relationship between ηsp/C and C, similarly to the usual non-ionizing polymer solutions; As the mass concentration of PNS reaches a value of 2g/100ml, the reduced viscosity seems to be independent of its concentration, the unchangeable ηsp/C can be defined as [ηsp/C],which may represents PNS molecular weight.The infrared spectrum analyzed both the function group of PNS and its molecular weight. A equation between [ηsp/C] and M is obtained by combination of FTIR and viscosity method just like a form of the famous Mark-Houwink equation. An examination has been designed to check its accuracy through commercial and synthesized products, Results showed the equation can be used to measure the molecular weight of PNS.For sodium salts of sulfonated naphthalene-formaldehyde condensates, higher molecular weight may bring better dispersant capability, The condensation process of PNS has been investigated carefully and thus a optimum synthesis conditions have been given.
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