Our experience has shown that optimal performance is achieved by replacing 10% to 15% of the cement with metakaolin. While it is possible to use less, the benefits are not fully realized until at least 10% metakaolin is used. The advantage of replacing some of the cement with metakaolin, rather than simply adding metakaolin to the mix, is that any existing color formulas or mix designs won’t change, or will only very slightly change. This is because the dosage of pigments and superplasticizers are based on the cement content in the concrete. Of course, it is ok to simply add metakaolin to an existing mix, but it’s important to realize that the total equivalent cement content will increase. Be aware that this will affect not only the pigment and admixture dosages but also the water to cement ratio, a critical factor in mix design.