Portland cement is one of the basic materials in the construction industry. The principal component of Portland cement is clinker. According to the cement nomenclature, clinker contains two silicate phases: Ca3SiO5 (alite) and Ca2SiO4 (belite), as well as aluminate and ferrite. The alite to belite ratio is responsible for the strength of Portland cement in cement clinker. The ability of determining this ratio already during the burning phase is essential for the evaluation of the cement’s final strength.