Concrete Admixtures

Admixtures are added to the concrete during or immediately before the mixing cycle. They are done to alter the properties of the concrete, and are generally limited to just one to maximize the predictability of the result. They are categorized into types by the ASTM (C494):

• Type A- Water Reducing: allows for a lower water content, improves the workability, and increases the efficiency of the Portland cement
• Type B- Retarding Agents- slows the hydration process, and be added before, during, or after the concrete is cast
• Type C- Accelerators- accelerating agents can be added to allow concrete setting in cold climates to avoid freezing, or just to speed up construction
• Type D- Water Reducing AND Retarding Agents
• Type E- Water Reducing AND Accelerators
• Type F- Water Reducing AND Superplasticizers- allows for a High Range mixture, allowing it to be pumped, and increasing flow for a short time
• Type G- Water Reducing AND Superplasticizers AND Retarding- will delay setting, but increases the length of time the concrete remains workable