The author would like to thank the NIST/NRC Postdoctoral Research Associateship Program for funding his research. He also thanks Ed Garboczi, Dale Bentz, and Paul Stutzman of the Inorganic Materials Group of the Materials and Construction Research Division of the Building and Fire Research Laboratory at NIST for many valuable discussions regarding this work and for providing detailed comments on the text. The author is grateful to Pietro Lura of the Danish Technical University for his careful reading of the manuscript and many comments and criticisms that helped to improve this work.