Effect of the fine chemistry of Portland cement clinker on its mineralogical composition

摘要

It is possible to determine the mineralogical composition of Portland cement clinker by analytical methods such as points counting, image analysis by mean of optical or scanning electron microscopy (OM or SEM), X ray analysis by Rietveld method, chemical selective dissolution or Bogue calculation. When applied to more complex system i.e. containing minor phases such as alcalies or mixed sulfates (alcalies, earth-alkalies), these methods are not sufficient to predict the total phase composition and further its consequence to the properties of the cement. In this paper, we use a trial and error method based on the microanalysis by microprobe of the main phases. This method allows a calculation of the percentage of the major phases fitting with the mass balance of the main four oxides in the range of the standard deviation of their chemical analysis. From the residu of the calculation, is then possible to identify the minor elements forming alcalies and earth alkalies sulfate and to estimate their quantity. It is shown that the effect of these minor elements on the mineralogical composition of the clinker can be decomposed into an indirect effect due to the modification of the burnability which induces a decrease in the alite content (and a simultaneous increase of the belite content) and a direct effect when new phases occur after the saturation of the major phases.