Mineralogical phase analysis of alkali and sulfate bearing belite rich laboratory clinkers: Fid-Bau Portal

Mineralogical phase analysis of alkali and sulfate bearing belite rich laboratory clinkers

Morsli, Khadija / de la Torre, Ángeles G. / Zahir, Mohammed / Aranda, Miguel A.G.

AbstractThe activation of laboratory belite clinkers has been carried out by adding variable amounts of alkaline salts (K2CO3, Na2CO3), and/or SO3 as gypsum in the raw materials but keeping almost constant the main elements ratios, Ca/Si/Al/Fe. Quantitative phase analyses by the Rietveld method using high resolution synchrotron and strictly monochromatic CuKα1 laboratory X-ray powder diffraction data has been performed. Quantitative phase analysis results have been compared to validate the protocol using laboratory X-ray data. The agreement in the results is noteworthy, which indicates that good quantitative phase analyses can be obtained from laboratory X-ray powder data. Qualitative studies have confirmed that the addition of alkaline salts to raw mixtures promotes the stabilization, at room temperature, of the highest temperature polymorphs: α′H-C2S and α-C2S. Quantitative studies gave the phase assemblage for ten different laboratory belite clinkers. As an example, an active belite clinker with 1.0 wt.% of K2O and 1.0 wt.% of Na2O (amounts added to the raw mixtures) contains 8.5(3) wt.% of β-C2S, 21.2(3) wt.% of α'H-C2S, 24.1(2) wt.% of α-C2S, 18.9(3) wt.% of total C3S, 17.3(2) wt.% of C3A and 10.0(2) wt.% of C4AF. A belite clinker with 0.8 wt.% SO3 (nominal loading) contains 60.7(1) wt.% of β-C2S, 6.7(2) wt.% of α′H-C2S, 12.3(7) wt.% of C3S, 9.1(2) wt.% of C3A and 11.2(2) wt.% of C4AF. Overall, quantitative phase analyses have shown that alkaline oxides stabilize α′H-C2S and α-C2S, sulfur stabilizes β-C2S, with a large unit cell volume, and the joint presence of alkaline oxides and sulfur promotes mainly the stabilization of the α′H-C2S polymorph.