Performance-based approach to durability of concrete containing flash-calcined metakaolin as cement replacement

• 25% of cement can be replaced by flash metakaolin for many categories of concretes.
• Substitution of cement by flash metakaolin improves the durability of concrete.
• Accelerated carbonation is the only durability test where metakaolin fails.

Performance-based specifications have recently been introduced into European standard EN 206-1 through the equivalent performance concept. This concept can be applied by comparing new concrete mixtures with reference mixtures. The present study deals with the performance and durability of concrete where flash-calcined metakaolin (MKF) was used as Portland cement replacement. The replacement rate was set at 25% of MKF in six different types of concrete, from immediate release concrete to self compacting concrete and from low to high performance concrete, including concrete for general or structural purpose. Many technical benefits for the concrete user, such as lower permeability, higher strength and decreased chloride ion penetration were found. It seems that MKF meets the requirements of the equivalent performance concept.