Quantitative analysis of sulphonated melamine formaldehyde superplasticizer in cement

Qualitative identification and quantitative analyses of superplasticizers are conventionally carried out by ultraviolet spectroscopy. This method is satisfactory for solutions of near-neutral pH, but for sulphonated melamine formaldehyde (SMF) materials it is unsatisfactory at higher pH values. In particular, the alkaline nature of cement gives rise to a high concentration of hydroxyl ions and this results in interference. The sample may be neutralized with acid, but this also results in ion interference. Spectrofluorimetry is shown to be a more satisfactory method: it can be used for SMF in solution in either fresh or set cement mixes with only minor pH adjustment. The procedures involved are described and as an example of the application of the method the sorption of SMF on freshly-mixed Portland cement and its hydration products is discussed.