Concrete admixtures is a liquid additive for concrete. It is sulfonated melamine formaldehyde (SMF) popularly known as melamine based super plasticizers. When water and cement are mixed, cement particles tend to agglomerate inhibiting dispersion in water. The super plasticizers when added to a concrete mix, increase the slump without addition of further water, provide uniform dispersion of cement agglomerates in the concrete and enhance concrete strength, density and finish ensuring effective cement utilization. The other major benefit is the production of high strength concrete at water cement ratio ranging from 0.30 to o.40 as super plasticizers reduces the water requirement by 10-30% without affecting the workability.
Super plasticizers are water soluble and the molecules can exert a strong fluidizing effect with major water reduction at constant fluidity and conveys an electrical charge to the particle surface favouring better dispersion (defloculation) of the particles via electrostatic repulsive forces. The chemical role of super plasticizers in cement paste interfere with nucleation and growth of the hydration product thus retarding the formation of connective gel which will help in maintaining fluidity (slump) for longer period.
- Super platicizers improves workability of concrete and covers total steel structures without increasing the water/cement ratio or rather reducing water requirement improving early & final compressive strength of concrete & reduction of concrete permeability.
- Super plasticizers reduce cement consumption promoting the use of fly ash in cementious system.
- Super plasticizers increase the concrete service life resulting from enhanced durability eliminating honeycomb structures and porosity & coating on steel structure reducing corrosion of steel reinforcement.
INSTRUCTION FOR APPLICATION:
The dosage of SMF depends on the flow effect required. Typical dosage of super plasticizers with grade 40 used to increase the workability of concrete ranges from 1-3 lit per cubic meter of concrete. For pre-cast concrete like paver blocks ,tiles and other articles 250gms to 350 gms per 50kgs of cement is usually recommended.
Super plasticizers are widely used in the construction of dams, bridges, canals and larg structures where high early strength is required and hence works best for precast concrete articles.
Typically recommended for use in slabs, beams, columns and areas of high steel congestion and thin section to achieve impermeable, honey comb free, high quality concrete, particularly roof slabs, water tanks, basement foundation and for pumpable concrete.