Estimation of the solubility limit of iron in tricalcium aluminate using different techniques

Abstract

Abstract Tricalcium aluminate (C 3 A) is one of the four main phases found in portland cement clinker. For this study Fe 2 O 3 was added to C 3 A in two ways. In the first, it was added to previously synthesized C 3 A by firing it at 1350°C for 3 h with intermediate grinding in air after each hour then quenching it in air. In the second mixture Fe 2 O 3 was added to the starting materials (CaCO 3 and Al 2 O 3 ) and fired at 1350°C for 15 h with intermediate grinding in air at 3 h intervals during firing then finally quenching it in air. The percentages of the Fe 2 O 3 added were 3, 4, 6, 8, 12, 16 and 20 wt.%. The extent of iron in solid solution was measured using an X-ray diffractometer, Mossbauer spectrometer, d.c. conductivity meter and magnetic susceptibility tests. It was found that the solubility limit of iron oxide (Fe 2 O 3 ) in C 3 A is about 4 wt.%. Mossbauer spectroscopy and magnetic susceptibility can be considered useful tools to estimate the solubility limit of iron in C 3 A. The sequence of adding iron to the C 3 A (either before or after firing) is found to affect the structural positions of the iron ions in the C 3 A structure.