Alite calcium sulfoaluminate cement: chemistry and thermodynamics

Calcium sulfoaluminate (C$A) cement is a binder of increasing interest to the cement industry and is undergoing rapid development. Current formulations do not contain alite; however, alite calcium sulfoaluminate (a-C$A) cements can combine the favourable characteristics of Portland cement (PC) with those of C$A cement while also having a lower carbon dioxide footprint than the current generation of PC clinkers. This paper presents two results on the formation of a-C$A clinkers. The first is a thermodynamic study demonstrating that the production of a-C$A clinker is possible without the use of mineralisers, doping with foreign elements, or using multiple stages of heating. It is established that a-C$A clinker can be readily produced in a standard process by controlling the oxygen and sulfur dioxide fugacity in the atmosphere. This allows for the stabilisation of ye’elimite to the higher temperatures required for alite stability. The second result establishes that when using fluorine to mineralise a-C$A clinker production, the iron content in the clinker is also an important variable. Although the exact mechanism of alite stabilisation is not known, it is shown that alite formation increases with the combination of calcium fluoride and iron (III) oxide in the mix

The electronic spectrum of AuO: A combined theoretical and experimental study

The near-infrared electronic spectrum of AuO1 has been re-examined in light of the new microwave data on the nu = 0 and nu = 1 vibrations of the X-2 Pi(3/2) state of AuO. The two observed bands in the spectrum, with red-degraded bandheads located at 10726 and 10665 cm(-1), have been reanalyzed. New theoretical work on AuO clarifies the electronic structure, and the bands in the infrared are now assigned as the (0,1) and (1,2) bands of the a(4)Sigma(-)(3/2) - X-2 Pi(3/2) transition, respectively