High concrete durability is one of the factors that can significantly decrease maintenance costs of structures exposed to severe environmental conditions. The mechanical and durability properties of high performance concrete with added metakaolin are studied in this book. Ten percent of the cement in the concrete mixtures was replaced by the metakaolin. In the experimental part of the book, frost resistance and resistance to scaling due to de-icing salts was measured. It was found that the type of added metakaolin does not have a significant influence on the results. The frost resistance of both types of concrete with added metakaolin satisfied code requirements and was comparable to the performance of air-entrained concrete. The resistance of concrete with metakaolin against salt-scaling was worse compared to air-entrained concrete. The experimental work proved that the type of the surface treatment for the scaling tests had major influence on the results. This analysis is especially useful to civil engineers responsible for durability of structures and highways. It can also interest anyone who may be considering replacing cement by metakaolin in concrete mixture design.