Some of the measurements presented here were performed during the summer of 1999, when D.P. Bentz was a visiting professor at the Department of Structural Engineering and Materials, DTU, funded by the Knud Hojgaard Foundation. The authors would like to thank Dr. Claus-Jochen Haecker of Dyckerhoff Zement for supplying the cements ground to the two extremes of fineness. D.P. Bentz would also like to acknowledge fruitful discussions with Dr. Daniel Quenard of Centre Scientifique et Technique du Batiment, Grenoble, France and to thank his wife, Janet Carey-Bentz, for the idea of using the Lego blocks as sample holders. Partial funding for this research was provided by the NIST Partnership for High Performance Concrete Technology (PHPCT) program.