Effect of Phosphorus Impurity on Tricalcium Silicate T₁: From Synthesis to Structural Characterization

Abstract

Alite is the major compound of anhydrous Portland cement: it is composed of tricalcium silicate Ca3SiO5 (C3S) modified in composition and crystal structure by ionic substitutions. Alite is also the main hydraulic phase of cement and the most important for subsequent strength development. Using raw meals (rich in Ca3P2O8) as alternative fuels in cement plants raises the question about the effect of phosphorus on C3S and its consequences on reactivity with water. This paper deals with a systematic study of C3S triclinic T1 polymorph doped with P2O5 in the range 0–0.9 wt%. All the samples were characterized by X‐ray powder diffraction (XRD), scanning electron microscopy (SEM), and electron‐microprobe analysis. The appearance of a phase rich in phosphorus is shown. It displays a structure derivative of the α′H–Ca2SiO4 polymorph, noted α′H–C2S(P). As phosphorus content increases, C3S is more and more decomposed into free lime and α′H–C2S(P). The α′H phase was detected from 0.1 wt% P2O5 and located at the interfaces of C3S grains. Two identification keys are proposed in order to highlight the α′H–C2S(P) phase: the XRD angular window at 2θCu=32.8°–33.2° and a smooth aspect on SEM micrographs.

Role of Municipal Sewage Sludge in Incorporating Cr, Ni, Cu, and Zn into Cement Clinker

“…First, C 2 S-C 3 P solid solutions such as Ca 2 SiO 4 ·0.05Ca 3 (PO 4 ) 2 and Ca 15 (PO 4 ) 2 (SiO 4 ) 6 were detected in the XRD pattern of RMCr. This phenomenon was similar to what was observed by Marie-Noe¨lle de Noirfontaine [38], who reported that adding phosphorus could cause partial decomposition of C 3 S into C 2 S and CaO phases, and that phosphorus was present in solid solution phases of C 2 S-C 3 P. Second, in the clinker samples of RMNi and RMCu, phosphorus was also present in such heavy metal-containing compounds as K 2 NiP 2 O 7 , K 2 Cu(PO 3 ) 4 , and Cu 4 O(PO 4 ) 2 . This indicates that parts of Cu and Ni were not incorporated in the calcium silicate phases but that they reacted with P and alkali metals.…”

CALPHAD formalism for Portland clinker: thermodynamic models and databases

“…Since the 1990s, the cement industry has used more and more alternative fuels (ratio up to 1/3), in order to favour the valorization of wastes and reduce the use of fossil fuels. This was the origin of new experimental studies related to the effects of minors, such as phosphorus when meat and bone meals are burnt [7]. These studies highlight the lack of knowledge of multi-component equilibrium phase diagrams.…”

High belite cement from alternative raw materials

“…According to the literature, the α′-belite phase is stabilized by P 2 O 5 (39,40) and concentration of up to 1.0% P 2 O 5 by mass in the clinker do not have an adverse effect on its properties (40). In this work the concentrations of the phosphate in the three clinkers is below 1% and lay in the range of 0.11-0.17%.…”