The first application of X-ray powder diffraction (XRD) to portland cement powder was made byBrownmiller and Bogue in 1930 [1], only 35 years after X-rays were discovered. At the time, portland cement clinker was thought to be composed primarily of either a complex single compound containing lime, alumina, and silica, or separate silicate compounds containing varying amounts of lime. In their groundbreaking study, Brownmiller and Bogue compared X-ray diffraction patterns obtained from a commercial portland cement clinker to those obtained from individually synthesized phases. The comparison (Fig. 1) demonstrated the presence of tricalcium silicate (alite) as the primary clinker phase, as postulated previously by Henri Le Chatelier [2, 3] and observed by Törnebohm [4], and also indicated phases that are now called belite (dicalcium silicate), tricalcium aluminate, ferrite, and periclase.