Influence of Sintering Time with Constant Temperature on the Development of the Tricalcium Silicate Crystallinity

Abstract

The article investigates the influence of the sintering time with constant temperature on the development of the tricalcium silicate crystallinity using the Scherrer's and Rietveld method.One suitable raw material mixture consisting of only pure CaCO3 and SiO2 in their specific ratio of 73.6:26.3 wt.% was selected. This raw material powder was prepared using a wet milling process in the water medium in a PULVERISETTE 6 plan mill. Based on previous research in this area, a firing temperature of 1500 °C was chosen with sintering period of 5, 10, 15 and 20 minutes in an experimental furnace with a manipulator for isothermal sintering of laboratory samples developed by Dr. Chromy. This furnace requires special sample preparation, so a procedure for their preparation was designed and optimized. Thanks to this optimization, it is possible to repeatably prepare identical pellets with the exact parameters for this type of furnace. The resulting pellet weight is 73 mg at a volumetric weight of 2,285 g·cm-3.The results of the firings with different sintering times and constant temperatures showed that the sintering processes and mineral conversion occur very quickly, since after 5 minutes 30.81 wt.% of the mineral tricalcium silicate was identified and after 20 minutes the raw powder was converted to tricalcium silicate in a significant amount, i.e., 72.02 wt.%. At the same time, the crystallinity was monitored using Scherrer's method and after 20 minutes of sintering, the crystallite size of tricalcium silicate reached 104.889 nm. Thus, there was a relatively rapid development of the crystallinity of Alite.