ROLE OF FE2O3 ON FORMATION KINETICS AND MICROSTRUCTURE OF CALCIUM SULPHOALUMINOFERRITE C4(A,F)3S

Experimental studies are reported on the CaO-Al2O3-Fe2O3-SO3 system in oxide ratios suitable for the formation of calcium sulphoaluminoferri tes in the temperature range 110-1300-degrees-C. The presence of Fe2O3 as a starting oxide or in the form of monocalcium ferrite (CF) strong ly accelerates the formation of calcium sulphoaluminoferrite (C4(A,F)3 SBAR) over the whole temperature range. In a sequence of reactions, mo nocalcium aluminate (CA) forms a solid solution with CF which is more reactive with CaSO4 as compared with pure CA. Electron probe microanal ysis of samples sintered in the presence of liquid phase showed that t he calcium sulphoaluminoferrite phase is a solid solution of Fe2O3 in C4A3SBAR, with a composition which can be expressed by the formula C4A 3-xFxSBAR. The grain size and the value of x depend on the amount of F e2O3 in the system.