Investigating the effect of CaO/MgO ratio on the structure and final properties of wall tile bodies in rapid firing using the primary sources of Borujerd talc and Abbas Abad calcium carbonate as primary sources

Abstract

AbstractIntroduction:In this research, the effect of CaO/MgO ratio, as the main oxides that activate the reactions during wall tile firing, was studied on the path of transformations and the formation of useful phases such as Anorthite, Diopside, and Wollastonite, and the reduction of the destructive phase of Gehlenite and free quartz.Methods: In the first part of the research, in order to determine the optimal amount of calcium carbonate as the main source of CaO supply, samples with 0, 6, 12 and 15% by weight were made. According to the obtained results, the sample with 12% by weight of calcium carbonate due to having less free quartz, more growth of Anorthite and less Gehlenite phase; Also, suitable water absorption of wall tiles, low coefficient of thermal expansion, lower moisture expansion percentage and suitable firing shrinkage percentage were selected as the best samples. In the second part of the research, mixtures with 12% by weight of calcium carbonate and 5%, 7% and 10% by weight of local soils supplying MgO in Iran (Broujerd talc) were made.Findings: After forming with a press, the mixtures were sintered in a fully industrial process and in a rapid baking furnace. By means of X-ray diffraction test and with the help of Rietveld refinement method which was carried out in Maud software, the weight percentage of the forming phases of the final microstructure was quantitatively calculated. By increasing the weight percentage of talc and decreasing the ratio of CaO/MgO to less than 4, the weight percentage of Diopside phase increased up to 15% by weight. Decreasing the ratio of CaO/MgO to less than 3 caused the growth of Diopside phase to decrease

Keywords

• wall tiles
• dilatometry
• water absorption
• thermal expansion
• firing shrinkage
• flexural strength