Melamine formaldehyde sulfonate effect

The effect of the interaction between two types of SPs (naphthalene formaldehyde sulfonates-NFS and melamine formaldehyde sulfonate-MFS) and the VEA on the fluidity of mortar is seen in Fig. 7.46. In the case of NFS, the mortar flow decreases with increasing addition of the VEA. This result indicates an appreciable interaction between NFS and the VEA. On the other hand, the fluidity of the mortar containing the MFS does not change. Measured amounts of the SPs showed that there was good correlation between the amount of SP adsorbed and observed fluidity. 

Chemical admixtures in small amounts are added to concrete to enhance the physical, mechanical, chemical, and durability characteristics of concrete. Superplasticizers are admixtures that have the ability to increase the workability of concrete (for easy placement), but also produce high strength concretes. The relative rates of hydration of cement containing superplasticizers at different temperatures are conveniently followed by conduction calorimetry. In Fig. 11 both the rates of hydration and the cumulative amounts of heat developed in cement pastes hydrated at temperatures of20,40, and 55" C are plotted as a function of time. In the figure, SMF refers to the superplasticizer based on sulfonated melamine formaldehyde. The addition of the superplasticizer retards the hydration of cement. The retardation increases with the dosage of the superplasticizer. Also, the retardation effect becomes less significant as the temperature of hydration is increased. 

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