Concrete Admixtures refer to ingredients other than cement which are added to concrete mixtures to change or control its properties to suit a certain construction situation. Below is a list of some common admixtures types and what they are used for:
Air Entrainment – The primary purpose of air entraining admixtures are to increase mass of void areas within the concrete permitting it to be more resistant to the freeze/thaw expand/contract phenomenon. Air Entrainment admixtures also increase the workability of wet concrete and when used in high quantities can be used to create lightweight nonstructural concrete with insulating properties.
Water Reducing Admixtures – The primary purpose of water reducing admixtures is to permit a reduced amount of mixing water while retaining the same amount of workability which results in higher strength concrete.
Superplasticizers (High-Range-Water-Reducers) – The primary purpose of Superplasticizer is to transform a stiff concrete mix into one which flows freely into place, used frequently in concrete wall and foundation settings. These admixtures are used for either increasing ease of placement or to reduce water content for higher strengths.
Accelerator – Accelerating admixtures cause concrete to cure more quickly. They are often used when cold weather is a factor that might inhibit or slow the cure of the concrete or when it is desired that the concrete set up faster than normal. Calcium chloride flake is the most common admixture for non-reinforced concrete (can speed up the corrosion process of corrosion). For steel reinforced concrete, non-chloride accelerators are commonly used, albeit they’re slightly more expensive.
Retarder – Retarding admixtures cause concrete to cure more slowly. They are often used when hot weather is a factor that might accelerate the curing or setting up of the concrete.