AC271 - Concrete Admixtures

Concrete admixtures are ingredients other than cement, water, and aggregates that are added to a concrete mix to change its properties. They can be chemical additives or mineral additions. For example, plasticizer or superplasticizer admixtures make fresh concrete flow more easily (improving workability) without adding extra water, and accelerators make concrete harden faster (useful in cold weather), while retarders slow down setting (helpful in hot weather or long transports).

Other admixtures include air-entraining agents that add tiny air bubbles for freeze-thaw durability, and fibers that reduce cracking. By using admixtures, concrete can be tailored to have higher strength, better durability, or other special characteristics as needed for a project. These enhancements work alongside requirements for cementitious exterior wall coatings (AC311) in comprehensive building envelope systems.

This acceptance criteria provides a basis for evaluating concrete admixture products that may not be directly covered by existing codes. It establishes testing protocols, performance requirements, and quality standards needed for code approval of these concrete modification systems.

• Nationwide acceptance by building officials for concrete admixtures
• Streamlined approval process for chemical and mineral additives
• Third-party verification of concrete performance enhancement claims
• Enhanced marketability for specialized concrete applications

• ICC Evaluation Service