Phase equilibria studies of CaO-SiO2-Al2O3-Fe2O3-MgO system using CALPHAD. (March 2018)

• Record Type: Journal Article
• Authors: Tazuddin, ; Aiyer, Hemantkumar N.; Chatterjee, Amit
• Is Part Of: Calphad. Volume 60(2018)
• Page Start: 116
• Page End: 125
• Publication Date: 2018-03
• Subjects: Thermodynamics -- CALPHAD -- Phase equilibria -- Phase diagrams -- Calcium silicate -- Calcium aluminate etc; Phase diagrams -- Data processing -- Periodicals; Thermochemistry -- Data processing -- Periodicals; Diagrammes de phases -- Informatique -- Périodiques; Thermochimie -- Informatique -- Périodiques; Thermodynamica; Electronic journals; 541.363
• DOI: 10.1016/j.calphad.2017.12.003
• Languages: English
• ISSNs: 0364-5916

Abstract

Abstract: A detailed CALPHAD (CALculation of PHAse Diagram) based thermodynamic study on CaO- SiO2 -Al2 O3 -Fe2 O3- MgO system (C-A-S-F-M) has been carried out to study the evolution of phases during heating and to investigate the effects of individual oxides. The important phases present at high temperature in the system are tricalcium silicate (C3 S), dicalcium silicate (C2 S), tricalcium aluminate (C3 A), dicalcium ferrite (C2 F) and a liquid phase. The evolution of liquid phase and other important phases predicted by CALPHAD closely matches with the experimental results. It was observed that in C-A-S-F-M system, there is a critical percentage of CaO and SiO2 at which C3 S is maximum. Both Fe2 O3 and Al2 O3 significantly increase the amount of liquid phase. Both Fe2 O3 and Al2 O3 reduce C3 S and increase C2 S in the system. Up to 1.5 wt%, MgO also helps in increasing liquid phase. A mathematical model to predict phases has been developed as an alternative to the Bougue's equation which is very effective in predicting phase fractions. Highlights: CALPHAD method has been applied for the prediction of Portland cement phases. CALPHAD result matches closely with XRD and Heating microscopy results. A critical percentage of CaO and SiO2 has been found to obtain maximum C3 S. Effect plot generated for comparative study of effect of individual oxides on phase formation. A standalone regression model developed to predict phases in C-A-S-F-M system in absence of Thermo-Calc.