Superplasticizer Admixture for Concrete

superplasticizer admixture is an essential component of concrete mix design because it can increase the workability of concrete without compromising its strength by increasing the water-cement ratio. For mass concrete, this is especially important because of shrinkage forces that can reduce concrete strength if the water-cement ratio is increased beyond a certain level.

Super plasticizers are formulated to change the slump of concrete and reduce water requirements by up to 40%, depending on the type of superplasticizer. Fritz-Pak manufactures both standard and premium super plasticizers, which can be used for small corrections to the mix on a job site or for more extreme changes in the slump.

Dosage of a superplasticizer is 0.5-1 % by weight of cementitious material, and it depends on the specific superplasticizer. Dosage should be determined by using the Marsh Cone Test (MCT) and can be adjusted as needed.

In addition to enhancing the workability of concrete, a superplasticizer can also improve rheological properties by increasing the flow and shrinkage of cement pastes. This is done by the adsorption of a polycarboxylate adsorbent on the cement particles.

This adsorption is dependent on the adsorption type, which can be divided into fast-adsorbing and slow-adsorbing polycarboxylates (PCEs). PCEs with high grafting degrees adsorb very quickly on reactive cement surfaces.

These PCEs adsorb on the surface of cement particles and agglomerates by Langmuir monolayer adsorption. This adsorption mechanism is based on the fact that the negative-charged surfactants repel each other and form a single layer of adsorption on the cement particles and agglomerates.