【摘 要】
：
Yeehmite is one ot the major constituents of Calcium SulphoAluminate type cements (CSA) and almost entirely responsible for the hydraulic reactivity at early age.It is well known that yeelimite can fo
【机 构】
：
HeidelbergCement Technology Center GmbH, 69181 Leimen, Germany
【出 处】
：
The 14th International Congress on the Chemistry of Cement (
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Yeehmite is one ot the major constituents of Calcium SulphoAluminate type cements (CSA) and almost entirely responsible for the hydraulic reactivity at early age.It is well known that yeelimite can form a broad range of solid solutions but the impact on the hydraulic reactivity is not well understood yet.Iron is one of the main elements that are incorporated into the crystal lattice to substitute for alumina.In this study we tried to synthesize C4A3-xFxs with x ranging from 0.0 (0% wt.-% Fe2O3) to 0.8 (≈19.5% wt.-% Fe2O3).The physical,chemical and mineralogical properties of the synthesized clinkers were characterized by a combination of specific surface area and particle size distribution measurements, X-ray diffraction, scanning electron microscopy and coupled with energy-dispersive X-ray spectroscopy.Furthermore, we assess the hydraulic reactivity by a multi method approach including isothermal conduction calorimetry, thermogravimetty and X ray diffraction for the pure clinker and in combination with different calcium sulphate sources.The measured maximum for x was found to be around 0.32 (≈8.1 wt.-% Fe2O3) and seems to depend on the Fe2O3/Al2O3-ratio of the raw mix.Moreover, a modification of the structure of yeelimite was observed.In addition, for some of the targeted clinker compositions the formation was incomplete as anhydrite, monocalcium aluminate and ferritic phases were present as minor X-ray detectable phases in most of the clinkers.The calorimetry measurements showed that the iron solid solutions have different hydration kinetics, in comparison to the neat yeelimite clinker.The addition of calcium sulphate, either anhydrite or gypsum, accelerates the reaction depending on x and on the calcium sulphate type used.The addition of anhydrite leads to only a slight shift of the main hydration peak of the specific sample to earlier times.In contrast, the main hydration peak, for all samples almost independent of x, occurs at more or less the same time
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