Has anyone tried metakaolin? This seems like really good stuff! "Metakaolin particles are nearly 10 times smaller than cement particles, which results in a denser, more impervious concrete. Using metakaolin in concrete increases the durability of concrete (i.e. resistance to chemical attacks, sulphate, ASR expansion, and freeze-thaw cycles). Metakaolin also enhances several mechanical properties (i.e. early-age compressive strength, and flexural strength) of concrete."

A privately held company, ACT markets its products both domestically and internationally through its office in Blaine, Washington USA. PowerPozz (HRM) is manufactured from high quality Kaolin Clay, mined and processed in Aiken, SC. There is a West Coast supply terminal in Stockton, CA for bagged and bulk product. No matter where you are located in the world, ACT has a superior transportation network to meet your delivery needs.

PowerPozz (HRM) is a proven alternative to Silica Fume. From elegant interior concrete fixtures, to large High Performance Concrete infrastructure projects, PowerPozz (HRM) has exceeded the design and performance criteria demanded by architects and engineers.

Here is a link that might be useful: metakaolin