Influence of sulphonated melamine formaldehyde superplasticizer on cement hydration and microstructure

This Paper assesses the role of sulphonated melamine formaldehyde (SMF) in cement. It is shown that the data given in the literature are frequently in error due to inappropriate analytical procedures. Initial rapid sorption of SMF occurs, probably on an ettringite precursor. This is followed by partial desorption of SMF, but eventually the alkaline nature of the cement pore fluid precipitates a chemically altered derivative for which some analytical data are given. The retarding effect of SMF is pronounced at 20°C but diminishes or disappears with increasing temperature up to 55°C. In comparable paste specimens SMF reduces the mean size of Ca(OH)₂ crystallites and alters their morphology, but promotes the growth of larger ettringite crystals.