Development of Crystallinity of Triclinic Polymorph of Tricalcium Silicate

Abstract

Tricalcium silicate phase is one of the main components of modern Portland cements. One of the major industrial challenges in the field of cement production is mapping the influence of individual clinker minerals and their polymorphs on the properties of industrially produced clinkers. The primary goal of this work is to improve the fundamental knowledge of understanding the process of alite formation and development from a crystallographic point of view. This study focuses on the observation of the crystallization process of triclinic alite during the firing process, which to date has not been thoroughly described. The effects of a wide range of temperatures and sintering periods on crystallinity were assessed on samples fired in platinum crucibles in a laboratory furnace. X-ray analysis—together with calculation of crystallinity using Scherrer’s equation—was used for observing the crystallite size changes of T1 alite polymorph. According to the acquired results, among the most technologically and economically advantageous regimes of production of a high-quality triclinic alite is the temperature of 1450 °C and sintering time of two hours. The most significant changes in the crystallite size occurred within the first hour of sintering for the whole investigated temperature range.

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

“…We selected a high-intensity diffraction line which covered the selected plane and, at the same time, did not overlap with other diffraction lines (especially beta-C2S), defined by the "hkl" Miller index of 445. Calculation of the size of the crystallite was based on the measurement of FWHM (full width at half maximum) and the Scherrer equation [8,11] with Warren correction [8,12] (Equation ( 2)):…”

“…These minerals together account for more than 90% of the total weight of clinker. These minerals are tricalcium silicate (Alite C3S), dicalcium silicate (Belite C2S), tricalcium aluminate (C3A) and finally tetracalcium aluminate ferrite (C4AF) [7,8].…”

“…This study presents a basic investigation of the fundamental processes involved in the formation and evolution of triclinic alite from a microscopic point of view. The present study focuses on monitoring the evolution of crystallite size during the sintering of the T1-allite polymorph; T1-allite was chosen because it can be prepared relatively easily by cooling a pure Ca3SiO5 compound [7][8][9].…”

“…The microscopic quantitative phase analysis forms a record for three separately fired clinker samples. This procedure greatly reduces the sampling error of both the raw powder and the heat treatment [7][8][9].…”

Formation, Stability, and Crystallinity of Various Tricalcium Aluminate Polymorphs

“…LaB 6 peaks were determined in the positions identical to the selected diffraction lines using HighScore plus software, see Figure 1. The FWHM values of LaB 6 were calculated from Equation (1) [34].…”