Superconductors (above water reducers)
Superplasticizers are substances that significantly reduce the amount of water in a concrete mix without changing the fluid or increase the amount of slump and fluid without changing the amount of water. Some types of these materials can reduce the amount of water in the mixture by 20 to 30%. The use of these additives leads to a rapid reduction in efficiency.
Water reducers (superplasticizers) are a class of additives that dramatically increase the workability of mortars and concretes by keeping the water-to-cement ratio constant. They usually have a temporary or variable duration of impact. Mortars and concretes with the same workability can be made with less water, with a reduction of more than 12% without delay in setting, excess air or harmful hydration.
Properties of superplasticizers
With a ratio of water to cement (W / C) , make concrete with higher workability than plain concrete.
At a constant (uniform) workability, they significantly reduce the water to cement ratio, resulting in the production of high-strength concrete.
Mechanism of operation of concrete superplasticizers
The mechanism of action of superplasticizer is mainly based on their ability to be adsorbed on cement particles and improve the rheologic behavior of the cement matrix. The adsorption rate of concrete superplasticizers depends on the mineral composition, softness (specific surface area) and the amount of cement. Calcium aluminate has been shown to absorb super-lubricating molecules very rapidly.
The act of increasing workability using superplasticizers is explained by the following properties. The amount of zeta potential of the double electric layer generated on the cement particles by the polar groups of the superplasticizer chains.
The molecular weight of superplasticizers and the rate of reduction of workability are related to the amount of time delayed setting in the hydration of the cement.
How to consume
Concrete superplasticizers are usually in liquid form with a content of 30 to 400% by weight of solid active ingredient. They are usually added to the cement mixture with mixing water. It has been found that adding them has a better performance after adding water to the mixture. Some superplasticizers are used as a powder. In this case, these materials are added to the materials and cement before adding water.
The effect of superplasticizer (high spectrum water reducing) on concrete properties
The specific gravity of concrete is increased by the use of superplasticizers.
Superplasticizers greatly increase the concrete’s ability to lubricate.
Adhesion is greatly increased by the use of concrete superplasticizers as a result of the reduction of concrete water.
The amount of air bubbles
The air bubble content of the concrete increases slightly, especially if the amount of additive used as a superplasticizer is high.
With uniform workability, slump loss in water-reducing concrete is higher than in concrete without additives. At a water-to-cement ratio, the slip reduction of superplasticized concrete is higher or lower than that of control concrete.
Ability to pump
The pumpability of concrete is improved by using superplasticizer as a result of increased workability and in the case of using high spectrum water reducing by increasing adhesion.
Grain separation is reduced in both cases where the additive is used as a superplasticizer, provided the concrete design is correct.
Normally, when the additive is used as a superplasticizer, it slightly delays the setting of the concrete. However, when used as a water reducer with normal (correct) consumption, it does not cause a significant delay.
Plastic shrinkage can be increased by the use of concrete superplasticizers.
Reduces the use of concrete superplasticizers. If the design is incorrect, hydration can be increased by adding superplasticizer to the concrete.
Resistance increases significantly when concrete superplasticizers are used due to water depletion, while resistance does not substantially improve with the use of superplasticizers.