Plasticizers and superplasticizers
They are by far the most widely used admixtures for making concrete. Plasticizers have a “reduced” effect because they are less concentrated or come from wood or corn derivatives. The more powerful superplasticizers come from the sodium gluconate Malaysia.
The mode of action of these adjuvants can be described as follows:
For a constant W / C ratio, superplasticizers improve the workability of concrete (A). This mode of action is sought after to extend workability times or to concrete in hot weather. The comfort of use, and therefore the quality of the embodiments, are greatly improved when the superplasticizer is thus used.
With constant workability, superplasticizers make it possible to reduce the water required, and therefore the W / C (B) ratio. Plasticizers allow this ratio to be reduced by at least 5% and superplasticizers by at least 12%. This results in an increase in strength, compactness and durability of concrete. The properties of concrete are almost all improved when the superplasticizer is used to reduce the amount of water.
In practice, a combined action (C) is obtained, more or less pronounced in one direction or the other.
The interest of superplasticizers is found in the optimization of the factors cost, workability and final characteristics of concrete. Superplasticizers have become essential in the production of common concrete and obviously for high performance concretes (BHP) and self-consolidating concretes (SCC).
As a side effect of superplasticizers, it is necessary to point out a slowing down of the setting in the event of too high a dosage, and sometimes difﬁculties in adjusting the percentage of entrained air in combination with the air entrainers. A high dosage of superplasticizer can also cause a large and unwanted increase in concrete viscosity.
It is important to check the good compatibility between cements (and to a lesser extent, aggregates) and these types of admixture, especially in case of high dosage or when using several admixtures at the same time.
It is also important to take into account the pot life of superplasticizers. This time is generally reduced if the temperature increases. It is common practice in ready-mixed concrete in Belgium to (partially) dose the superplasticizer when it arrives on site.
For more content like this, click here.