The different types of chemical admixtures are used in concrete construction in order to enhance the performance of concrete.
Concrete admixtures are not the major component of the mixture, but nowadays their use in concrete is rapidly increasing and their importance is becoming more valuable.
Main Function of Admixtures:
- To accelerate or retard the setting time of fresh concrete.
- To improve the workability or flowability of concrete.
- To increase the strength and durability of concrete.
- To decrease the heat of hydration.
- To reduce the segregation and bleeding.
- To decrease the permeability.
- To achieve other desired properties.
Types of Chemical Admixtures
1. ACCELERATING ADMIXTURES
This type of admixture is commonly added in concrete to increase the rate of hydration of hydraulic cement and for shortening the setting time. Calcium chloride is the most widely used accelerating admixture.
2. RETARDING ADMIXTURES
The main function of retarding admixtures is to delay the initial rate of hydration of cement and extend the setting time of the cement paste. This admixture can be used in high temperature and where the concrete has to be transported to a long distance.
3. WATER REDUCING ADMIXTURES
As the name implies, water reducers are added to a concrete mixture, mortar or grout to increase the flow-ability without increasing the water content. A great example of water reducing admixtures are the plasticizers and the concrete superplasticizer admixtures.
4. AIR-ENTRAINING ADMIXTURES
Air entraining admixtures help I producing a certain amount of air bubbles in the concrete mixture. It is to increase the resistance against freeze-thaw degradation and cohesion. Furthermore, it also improves the workability of fresh concrete without modifying the setting or the rate of hardening.
5. GROUTING ADMIXTURES
This type of admixtures is added to grout materials to improve the grout properties based on the requirement of grout. Sometimes, there is a need for quick set grout and a need for slow set grout to spread into deep cracks or fissures. Many construction chemicals suppliers in the UAE, like Corrotech, offers grouting chemical admixtures.
6. CORROSION PREVENTING ADMIXTURES
Corrosion of steel in a reinforced concrete structure is common and it is severe when the structure is exposed to harsh environments. To prevent or to slow down the process of corrosion, preventing admixtures are used.