Incorporation of minor constituents into Portland cement tricalcium silicate: Bond valence assessment of the alite M1 polymorph crystal structure using synchrotron XRPD data

Abstract

Six industrial clinker samples, produced using petroleum coke as kiln fuel, were analysed using high resolution synchrotron XRPD data, one sample (HM) presenting predominantly M1 C3S polymorph. Refinement of data collected on this sample was used to revise the M1 structural model, improving the Rwp and RB of the original model (from Rwp = 9.25 and RB = 5.517 in the original model to Rwp = 8.07 and RB = 2.965). The revised model was validated through bond length and Bond Valence Sum (BVS) distribution. Using the BVS method, two preferential substitutional calcium sites were identified for Mg2+ and two silicon sites for Al3+, while two interstitial sites were identified for S6+ and Fe3+. Using the revised model for refinement of the six industrial clinker samples showed improvement in the Rwp and GoF indices. The amount of M1 and M3 polymorph present was found to be significantly different using the revised M1 C3S model.