Today it is usual that, instead of using a special cement, some properties can be changed by adding an element called an additive.
An additive is a material different from the normal ones in the composition of the concrete, this means that it is a material that is added immediately before, after or during the development of the mixture in order to improve the properties of the concrete, such as resistance, workability , setting, durability, etc.
There are many of these products on the market and they are available in a liquid or solid, powder or paste state.
The most commonly used additives today can be classified as follows:
1.-Air entrainers: It is the additive that, when added to the concrete mix, creates an increase in its air content, causing, on the one hand, an increase in workability and resistance to freezing and, on the other hand, the reduction in bleeding (when water comes out of the concrete). Bleeding is a form of segregation in which a part of the water in the mix tends to rise to the surface) and segregation (segregation is when the materials that make up the concrete are separated, when there is segregation in the mix, it occurs a concentration of coarse materials in some areas, while the others contain a concentration of finer materials.
2.- Fluidizers: These additives cause an increase in the fluidity of the mixture and in turn allow the reduction of the water required to obtain a mixture of a certain consistency, which results in an increase in workability, while maintaining the same slump. In addition, they can cause increases in resistance to both freezing and sulfates and improve adhesion.
3.- Setting retardants: These additives retard the initial setting time of the mixtures and therefore affect their resistance at early ages. They can decrease the initial resistance. They are recommended for hot climates, large volumes or long transportation times.
4.- Strength accelerators: These produce an advance in the initial setting time by accelerating the strength at early ages. It is recommended to use them in low temperatures to advance strikes. In addition, they can decrease the final resistance.
5.-Volume stabilizers: They cause a controlled expansion that compensates for the contraction of the mixture during setting. It is recommended to use them in support bases for machinery, fillings and patching.
6.- Hardeners: These additives increase the resistance to wear caused by impact effects and vibrations. They reduce the formation of dust.