Concrete admixtures speaks to why concrete admixtures and what are concrete admixtures.
They are the other ingredients other than cement which are used to make concrete such as cementitious materials, aggregates and water. The addition of different admixtures will alter the properties if concrete in a variety of ways.
Coloring agents are dyes and pigments used to alter and control the colour of concrete for building components when for atheistic reasons appearance is of importance.
These agents improve the plasticity characteristics of wet concrete to make it easier to place in forms and finish. They include pozzolans and air entraining admixtures along with certain fly ashes and organic compounds.
These agents increase the workability of the wet concrete, reduce freeze-thaw damage and if used in larger amounts, result in very lightweight non-structural concretes having thermal insulating properties.
Water Reducing Admixtures
Water reducing admixtures allow a reduction in the amount of mixing water while retaining the same workability, which results in a higher strength concrete.
High-Range Water-Reducing Admixtures
These admixtures are also known as superplasticizers and are organic compounds that transform a stiff concrete mix into one that easily pours into the forms. They are used to either facilitate placement of concrete under difficult conditions or to reduce the water content of a concrete mix in order to increase its strength.
Extended Set-Control Admixtures
These admixtures may be used to delay the curing reaction in concrete for any period up to several days. They include two components, the stabilizer , added at the time of initial mixing, which defers the onset of curing for an indefinite period of time and the activator, added when desired which reinitiates the curing process.
Accelerating admixtures cause concrete to cure more rapidly and retard admixtures slow the curing which allows more time to work with the wet concrete.
Shrinkage Reducing Admixtures
These admixtures reduce drying shrinkage and any subsequent cracking.
Corrosion inhibitors are used to reduce rusting of reinforcing steel in structures that are exposed to road salts or other corrosion causing chemicals.
Freeze Protection Admixtures
These admixtures allow concrete to cure satisfactorily at temperatures as low as 20 degrees F or 7degrees C.