Traditional X-ray methods are extensively applied to commercial cement samples in order to determine their physical and chemical properties. Powder patterns are routinely used to quantify the composition of these phase mixtures, but structure determination becomes difficult because of reflection overlapping caused by the high number of different crystal structures. The fast-growing 3D electron diffraction technique and its related automated acquisition protocols arise as a potentially very interesting tool for the cement industry, since they enable the fast and systematic acquisition of diffraction data from individual particles. In this context, electron diffraction has been used in the investigation of the different crystalline phases present in various commercial clinkers for cement. Automated data collection procedures and subsequent data processing have enabled the structural characterization of the different crystal structures from which the α'H polymorph of Ca2SiO4 (belite) exhibited satellite reflections. Its average crystal structure has been known since 1971 and satellite reflections have been reported previously, yet the modulation was never fully described by means of the superspace formalism. Here, the incommensurately modulated structure is solved and refined using harmonic and crenel functions in the superspace group Pnma(α00)0ss, showing the potential of 3D electron diffraction for systematic crystallographic characterizations of cement. A full description of the different belite polymorphs is provided considering this modulated structure.

A hydraulic binder includes, in parts by mass: (a) from 20 to 60 parts of Portland clinker; (b) from 20 to 40 parts of slag; and (c) from 0 to 60 parts of inorganic material other than the clinker and the slag; the sum of (a), (b) and (c) being equal to 100 parts; which binder further includes a slag activator including, relative to 100 parts of the sum of (a) and (b): from 1.4 to 6.55 parts of alkali metal salt, expressed as equivalent-Na2O; and from 1.1 to 11.0 parts of calcium sulfate, expressed as SO3.

The present invention relates to the production of a ternesite-belite-calcium sulfoaluminate (ferrite) clinker. The invention also relates to the use of alternative raw materials for clinker production, for example raw materials based on industrial byproducts, including those of low quality, such as lump slag and ash having a low glass content and/or a high free lime content and/or a high content of crystalline high-temperature phases, as well as naturally occurring rocks and rock glasses of comparative chemical composition.

The invention relates to a process and a plant for producing cement clinker, which has a furnace system and has essentially the following process steps:—raw material is preheated in a preheater by means of hot offgases from the furnace system,—dust is removed from the hot offgas downstream of the preheater in a preliminary dust removal apparatus to a residual dust concentration of max. 20 g/standard m3,—the offgas which has been subjected to preliminary dust removal is purified in a selective catalytic flue gas purification plant (selective catalytic reduction, SCR),—at least part of the offgas purified in the flue gas purification plant is conveyed in a bypass around a raw material milling plant to a cooling device and cooled there to temperatures of max. 140° C.,—before the residual dust in the offgas is precipitated in a process filter and—at least part of the residual dust precipitated in the process filter is discharged for removal of mercury.