Effect of Superplasticizer on Fresh Concrete

effect of superplasticizer on fresh concrete

The effect of a superplasticizer on the properties of fresh concrete is largely dependent on type and dosage. A superplasticizer is used to optimize the water-cement ratio, workability and strength of concrete. It can also improve the flow of concrete and enhance self-leveling characteristics by reducing the water content.

In the initial stages of hydration, the superplasticizer promotes a strong hydration reaction by breaking links between cement particles which results in higher fluidity and permeability. It also lowers the w/b ration of the cement resulting in increased early strength and improved durability.

It can be used as a primary admixture in mixtures of self-compacting concrete for improved durability, or as a secondary admixture with other water-reducing additives in high strength and hardened concrete to minimize the use of water-retaining curing agents.

This admixture can be mixed with dry ingredients, or added to the water 10-15 minutes prior to casting. It can be also added to concrete during mixing in mechanical drill or mortar mixer (mixing time is 3 minutes).

The most important advantage of using a superplasticizer is that it does not increase the amount of air in the mix. This air may enhance the workability of concrete, but it also reduces durability if the mix is not fully cured before application.

It is recommended that a superplasticizer be applied when the concrete is at its peak of workability and before it reaches the slump loss that would normally occur. It is also advisable to avoid adding air-entrained concrete with this admixture as it is prone to microbial attack.