The amount of water required for hydration reaction at the concrete mix is approximately 25% of cement mass. however, this amount is inadequate to produce workable concrete. approximately 50% of cement mass is required to produce workable concrete.
The excess water will evaporate and increase concrete porosity this will ease ingress of aggressive chemical such as chloride. using of superplasticizer is a reliable solution to produce workable concrete with lower W/C. In 1960 Japan and Germany initiated the use of superplasticizer. construction management: concrete construction
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superplasticizer are classified according to their polymer group into:
- Sulfonated melamine-formaldehyde condensates (SMF)
- Sulfonated naphthalene-formaldehyde condensates (SNF)
- Modified lignosulfonates (MLS)
- Polycarboxylate derivatives
superplasticizers are linked to change in interparticle forces. the superplasticizer dispersing or Defloculation the particle of concrete mix allowing water to perform more effectively but there is no accurate understanding of the dispersion mechanism whether it due to electrostatic, steric, entropic or capillary effects or any combination of these. The advantages of using superplasticizer:
- significantly improving concrete workability without increasing W/C.
- producing concrete with high strength due to reducing W/C. this concrete will be suitable for post-tensioning and precast concrete.
- reducing the permeability of concrete.this will significantly delay the effects of the aggressive chemical in concrete. as a result concrete durability improved significantly.