Formation of belite clusters from quartz grains in portland cement clinker

✍ Scribed by I. Maki; K. Fukuda; T. Imura; H. Yoshida; S. Ito

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 421 KB
• Volume: 25
• Category: Article
• ISSN: 0008-8846
• DOI: 10.1016/0008-8846(95)00074-m

✦ Synopsis

The conversion process of quartz grains into belite clusters in portland cement clinker has been followed under isothermal heating conditions at 1400°C. On heating, quartz grains are surrounded by layers consisting of belite and liquid, which continue to grow thick with the progress of conversion (outer layers of belite). The conversion process has been divided into three stages considering the chemical composition of the liquid phase formed in each stage. In the first stage are formed two kinds of liquids the compositions of which lie across the primary phase field of wollastonite from each other. The belite crystals precipitated constitute thin, dense layers (inner layers of belite). At the beginning of the second stage, the inside of the belite layers is completely converted into a liquid without quartz and wollastonite. The inner layers extend inward and grow thick; the impurity concentration is lowest for this part of the belite layers. With further progress of diffusion, belite crystals nucleate and grow independently inside the layers. The composition of the coexisting liquid, rich in alkalies, moves on the primary phase field of C,S toward that of C,A. In the third stage the conversion is completed and the liquid phase, enriched with AI,O, and Fe,O,, is similar in composition to the interstitial liquid in portland cement clinker. The belite crystals, especially those of the inner layers, undergo grain growth with an increase in impurity content with duration of heating. Three kinds of belite crystals different in origin, texture and composition are thus distinguishable in the belite clusters.