Categorization of Concrete Admixture and various uses
Concrete admixture belongs to the material excluding the other materials like aggregate, water and cement which are included to the concrete. The performance of concrete is improved with the application of perfect admixture.
Categories of Concrete Admixture and their Uses:
• Air entraining concrete admixture
• Water reducing admixture
• Retarding concrete admixture
• Accelerating concrete admixture
• Calcium chloride
Given below the details and uses of these admixtures:
• Air Entraining Concrete Admixture
• Air entraining concrete admixture is mainly applied to make the resistance power for freezing and thawing better. They also provide superior resistance to deicing chemicals, enhance flexibility, diminish water demands for a specific slump, decrease the amount of fine aggregate required in the mixture, lessen segregation and bleeding, augment strength, and enhance pumpability.
Set Retarding Concrete Admixture: These agents are principally utilized for deferring the setting time of concrete. Set retards are beneficial, but do not provide solution to poorly designed mixes, substandard materials, or low cement factors.
The set retarder should be distributed during the course of the whole mix equally. If it is not done, it will lead to the admixture leftover in voids, affecting some areas to sustain plastic. It results in plastic shrinkage.
Accelerating Concrete Admixture: Accelerating concrete admixture is mostly suitable to curtail the setting time and enhance the initial strength of the concrete. These agents are specifically utilized for concrete requiring to be applied on immediate basis.
Calcium Chloride: Calcium chloride is normally applied in cold weather to accelerate the setting time and makes an early finish of the concrete.
Calcium chloride can influence the characteristics of concrete and it can lead to increase of temperature & internal stresses, erosion of insecure reinforcement, a reduction in the resistance to freeze, an upsurge in the attack of sulfates, and an upsurge in the amount of drying shrinkage among 10 to 50 %.