Cement News tagged under: cement chemistry

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Magnesia in clinker

18 November 2019, Published under Cement News

Magnesia is often present in clinker as periclase, which is formed of free MgO. However, periclase does not always provide a welcome part of the clinker’s composition and can lead to significant volume expansion of the concrete that is made with cement manufactured from such clinkers. Figure 1: periclase inclusions in belite. The belite crystal with two inclusions is 12µm across In cement clinker magnesia (MgO) can be present as a substituent in each of the primary clinker miner...

New supplementary cementitious materials

19 August 2019, Published under Cement News

The search for new supplementary cementitious materials (SCMs) is ongoing. A recent review of existing SCMs and the potential for new ones caught the eye of Arthur Harrisson and provided further potential for investigation. A disused slate quarry: a potential SCM? A recent review 1 of the availability of supplementary cementitious materials (SCMs) and the possibility for expanding the choice of those available examined the range of emerging SCM sources and also the means of tes...

Belite appearance in clinkers

11 April 2019, Published under Cement News

This 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 clinker

26 November 2018, Published under Cement News

The 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 microscopy

30 October 2017, Published under Cement News

Microscopical 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 development

31 May 2017, Published under Cement News

This 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 target

23 November 2016, Published under Cement News

While 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 ignition

28 September 2016, Published under Cement News

The 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 clinker

10 August 2016, Published under Cement News

The 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 cements

27 July 2016, Published under Cement News

While 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...