Durability Enhancing Concrete Admixtures

Air Entraining – Corrosion Inhibiting – ASR Inhibiting – Shrinkage Reducing – Permeability Reducing

Air Entraining Admixtures:

The most common type of durability enhancing admixture, air entraining admixtures create microscopic bubbles within the concrete that provide the following benefits:

  • Protects Against Freeze Thaw Cycles
  • Increases Workability
  • Reduces Bleeding & Segregation
  • Increases Strength

Corrosion Inhibiting Admixtures:

  • Corrosion Inhibitors are added to the concrete mix to reduce chloride induced corrosion of reinforcing steel.
  • Forms a protective layer at the steel’s outer layer due to the chemical reaction that takes place.
  • Often used in situations where de-icing salts or other chemicals will come in contact with the concrete.

ASR Inhibiting Admixtures (ASR’s):

  • ASR Inhibitors are added to the concrete mix to reduce alkali-silica activity.
  • The alkalis in concrete react with the silica in aggregates that produces a gel. This gel begins to expand when it comes in contact with moisture. The gel’s expansion creates pressure within the concrete and causes cracking.
  • ASR Inhibitors are not frequently used but are applied when concrete is high in alkali.

Shrinkage Reducing Admixtures (SRA’s):

SRA’s reduce cracking due to shrinkage during hydration by reducing capillary action of pore water. Some of the main benefits include:

  • Reduced Curling
  • Reduction of Shrinkage Cracks
  • Reduction of Shrinkage Cracks

Permeability Reducing Admixtures (PRA’s):

  • PRA’s increase concrete’s durability by decreasing the capillary action that takes place within the concrete. This can lead to corrosion of reinforcement or increased susceptibility to freeze-thaw cycles.
  • PRA’s are most frequently used in slabs that will be consistently exposed to moisture and that have flooring installed. This typically requires as surface applied adhesive that would react negatively with water.