In 2004, the Canadian Centre for Mineral and Energy Technology (CANMET), in association with the American Concrete Institute, the Electric Power Research Institute, Palo Alto, CA, UWM Center for By-Products Utilization, Milwaukee, WI, and several other organizations in Canada, sponsored the Eighth CANMET/ACI International Conference on Fly Ash, Silica Fume, Slag and Natural Pozzolans in Concrete. The conference was held in Las Vegas, Nevada, U.S.A., May 23-29, 2004. The proceedings of the conference containing 56 refereed papers from more than 20 countries were published as ACI Symposiuml Publication SP-221.