Cement News tagged under: cement chemistry
Belite appearance in clinkers11 April 2019, Published under Cement NewsThis month Arthur Harrisson looks at the second-most abundant constituent of cement – belite – and its appearance in clinkers. Figure 1: Type I belite with multiple sets of parallel laminations. The blue crystals are alite Of the four main constituents of cement clinker, the tricalcium silicate known as alite is the most abundant and is the one that is conventionally maximised to react with water to produce calcium silicate hydrate, the material required to achieve strength in a... |
Sulphate in clinker26 November 2018, Published under Cement NewsThe amount of sulphate (SO 3 ) varies widely in cement clinker. Arthur Harrisson discusses the sources of SO 3 and its impact on clinker composition. Figure 1: relationship between the contents of sulphate and aluminate in alite crystals from two cement plants The four main phases in Portland cement clinker are alite (C 3 S), belite (C 2 S), aluminate (C 3 A) and ferrite (C 4 AF). As has frequently been discussed, the chemical compositions suggested in brackets for these compou... |
Raw material microscopy30 October 2017, Published under Cement NewsMicroscopical methods are key tools in the assessment of potential raw materials to be used in the production of high-quality cement. This month ICR considers the use of optical microscopy in the determination of the mineral composition of the rocks under investigation. Figure 1: kiln feed viewed in plain-polarised light Assessment of potential raw materials involves many lines of enquiry. The chemical composition, geological variation, accessibility and consistency are essentia... |
Early strength development31 May 2017, Published under Cement NewsThis month Arthur Harrisson discusses early strength development in concrete, which is affected by many variables in practice. In the two-stage process, which includes a setting and a hardening phase, he observes the parts played by sulphates and C3A while acknowledging the importance of other factors such as the C3S content. Cement hydrates five hours after mixing Several studies of which factors influence early strength performance have been carried out under controlled condit... |
Achieving the target23 November 2016, Published under Cement NewsWhile achieving targets is commonplace in the cement industry, when it comes to quality, there are a few key parameters that determine the final product in the cement production process. Figure 1: some of the large amounts of data that are routinely collected in a modern cement plant Maintaining quality in the cement industry involves meeting a wide range of targets for raw material composition, raw meal fineness, kiln feed composition, clinker composition and mineralogy, cement... |
Loss on ignition28 September 2016, Published under Cement NewsThe loss on ignition of a raw material, cement or a clinker sample is the amount of weight lost through raising the temperature of the material to a predetermined level. As an indicator it can be used to monitor and improve the quality of the final product. Clinker stored outside in wet conditions will experience an increase in LOI Weight loss during heating can be due to the evaporation or volatilisation of a variety of components of the sample. Water is lost at 100-105˚C, orga... |
Crystal inclusions in Portland cement clinker10 August 2016, Published under Cement NewsThe nature of inclusions in clinker crystals provides clues about the burning environment and are therefore important indicators of clinker quality. Figure 1: blue belite inclusions in alite crystals Of the four main crystalline compounds that are found in Portland cement clinker, two are produced as solids and two are present in the burning zone of the cement kiln as a liquid, which then crystallises on cooling. Microscopic examination of clinker has been employed as a quali... |
Fly ash and slag cements27 July 2016, Published under Cement NewsWhile cements containing fly ash or GGBS have different strength properties to ordinary Portland cement, they also benefit from improved durability and workability. A key factor in strength development is the provision of calcium silicate hydrate. Concrete made with cement which includes fly ash or ggbs will have different strength properties than that made with cement which contains purely clinker and gypsum Although a particular material may be cheaper per kilogram or per t... |
Clinker cooling16 March 2015, Published under Cement NewsDescriptions of the formation of cement clinker generally concentrate on those reactions that take place as the kiln feed heats up and passes through the process to the burning zone. The part of the operation after the burning zone and up until the clinker’s eventual delivery to the cement mill can also have a significant effect on the quality of cement produced. Figure 1: zoned C3S crystal with C2S inclusions in a finely divided groundmass. (Field of view is 90µm) In a precalci... |
Reducing LSF13 October 2014, Published under Cement NewsJust over a year ago an article in ICR discussed the possibilities for reducing CO 2 emissions from a cement plant. 1 One option was to use less limestone in the kiln feed, thus reducing the CO 2 released by calcination (both by dissociation of CaCO 3 and because most fuel is used in calcination) and making the kiln feed easier to burn in the burning zone (which therefore requires less fuel). But what are the quality implications of such a reduction and how might they be overcome? ... |