High‐Temperature Microscopic Investigation of Tricalcium Silicate and Dicalcium Silicate Phases in Portland Cement Clinker

Birefringence was measured as a function of temperature up to 1400°C for (1) alite and various types of belite in portland cement clinker, and (2) alite in fused cement. The characteristic optical changes in alite and belite grains which accompany polymorphic transformations and facilitate, in certain cases, determination of the modification without necessitating the separation of the pure phase are given. The β and α’modifications were differentiated for belite from clinker and also for alite in fused cement. A method is described for measuring birefringence of minerals at high temperatures, as well as the apparatus and the preparation of samples.