Effect of calcination process on ferrite phase and silicate phase of ferrite-belite-rich Portland cement clinker from industrial solid waste

Abstract

In this paper, the industrial solid waste with potential cementitious activity was used to prepare ferrite-belite-rich Portland cement clinker. The changes in solid waste composition, raw meal ratio, calcination temperature, and holding time on the type and content of iron aluminate phase and silicate phase in the clinker were studied. The effects of flue gas desulfurization gypsum on the mechanical properties of clinker, mineral composition, and microstructure of hardened slurry were briefly discussed. In addition, the sustainability of the production of ferrite-belite-rich Portland cement clinker was evaluated by using a life cycle assessment. The analysis results show that: (1) The content of the ferrite phase increased first and then decreased with the increase of calcination temperature, and the content of the silicate phase and ferrite phase increased first and then decreased with the extension of holding time. (2) With the change of calcination temperature, the silicate phase is always cobblestone-like and evenly distributed. The ferrite phase changes from granular or flake to branch dendritic, and finally is swallowed by the liquid phase, filled between the gaps of the silicate phase structure, or attached to the surface of the silicate phase. (3) The Si elements in the clinker are always agglomerated in cobblestone shapes with uneven sizes. With the holding time from 30 min to 60 min, the distribution area of Al and Fe elements in the gaps of silicate phases increased gradually. Some Al and Fe elements are distributed in the area where silicate phase minerals are located. When the holding time is extended to 90 min, Fe and Al elements tend to be randomly distributed. (4) Fe will replace part of Al to form Fe-ettringite, Fe-siliceous hydrogarnet, etc. in the hydration process of C4AF. (5) The use of red mud, carbide slag, and silica fume to produce ferrite-belite-rich Portland cement clinker will reduce carbon emissions by 57.50%.