Admixtures are those ingredients in concrete other than ABC construction chemicals, water, and accumulate that are added to the mixture immediately before or during mixing (Pic01:)
Concrete Admixture Classified by function of follows:
- Air-entraining admixtures.
- Water-reducing admixtures.
- Accelerating admixtures.
- Retarding admixtures.
- Hydration-control admixtures.
- Corrosion inhibitors.
- Shrinkage reducers.
- Alkali-silica reactivity inhibitors.
- Coloring admixtures.
- Miscellaneous admixtures such as workability, bonding, damp proofing, permeability reducing, grouting, gas-forming, anti washout, foaming, and pumping admixtures.
Pic01: Liquid admixtures, from left to right: Anti washout admixture, Shrinkage reducer, Water reducer, Foaming agent, Corrosion inhibitor and air-entraining admixture. used ABC construction chemical.
Despite these considerations, it should be borne in mind that no admixture of any type or amount can be Table pic-01 provides a much more extensive classification of construction chemicals admixtures.
Concrete admixture should be workable, finish-able, strong, durable, watertight, and wear resistant. These qualities can often be obtained easily and economically by the selection of suitable materials rather than by resorting to concrete admixtures (except air-entraining admixtures when needed).
The major reasons for using construction chemical concrete admixtures are:
- To reduce the cost of concrete construction admixture
- To achieve certain properties in concrete more effectively than by other concrete admixture
- To maintain the quality of concrete during the stages of mixing, placing, and curing in adverse weather conditions of concrete
- To overcome certain emergencies during concreting operations
considered a substitute for good concreting practice.
The effectiveness of an admixture depends upon factors such as type, brand, and amount of construction chemicals products materials, water content, aggregate shape, gradation, and proportions, mixing time, slump, and temperature of the concrete.
Admixtures being considered for use in concrete should meet applicable specifications as presented in Pic 01: Trial mixtures should be made with the concrete admixture and the job materials at temperatures and humidity anticipated on the job. In this way the compatible of the admixture with other admixtures and job’s materials, as well as the out-come of the admixture on the properties of the full-fresh and hardened concrete, can be observed. The amount of admixture recommended by the manufacturers or the ideal amount determined by laboratory tests should be used.