Concrete admixtures are natural or manufactured chemicals or additives added during concrete mixing to enhance specific properties of the fresh or hardened concrete. These properties can include workability, durability, and early and final strength12. There are two main types of concrete admixtures:
- Chemical Admixtures:
- These reduce construction costs, modify properties of hardened concrete, and ensure quality during mixing, transporting, placing, and curing.
- Categories include:
- Air entrainers: Improve freeze-thaw resistance and workability.
- Water reducers: Enhance workability and reduce water content.
- Set retarders: Delay concrete setting time.
- Set accelerators: Speed up concrete strength development.
- Superplasticizers: Improve flowability without increasing water content.
- Specialty admixtures: Address corrosion, shrinkage, alkali-silica reactivity, and coloring.
- Mineral Admixtures:
- These make mixtures more economical, reduce permeability, increase strength, and influence other concrete properties.
- Examples include pozzolans (such as fly ash and silica fume) that react with cement to enhance performance