Cement News tagged under: cement chemistry

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Maintaining quality with emission limits

19 December 2023, Published under Cement News

The trend towards more sustainable cement production and decarbonisation has resulted in increased emissions control. While this has led to challenges in terms of maintaining quality, solutions are continually being discovered. Figure 1: alite in the bottom right quadrant contains inclusions of free lime due to a high SO 3 content in the clinker (© A Harrisson) In the past couple of decades the cement industry has seen a number of changes in technology and priorities, which...

Influencers of strength

21 March 2022, Published under Cement News

Over the years several factors that influence the strength of cement have been determined. These include mineralogy, chemistry, microstructure and process.   Figure 1: central irregular alite growth with many inclusions surrounded by clearer alite growth The various influences on the strengths achieved by Portland cements has been the subject of a number of research projects in the laboratory as well as analyses of industrially-produced materials over the years. A useful method ...

Limestone specifications

23 November 2021, Published under Cement News

When asked to review the suitability of limestone deposits for cement manufacture, Dr Michael Clark makes a range of important assessments such as what other materials would need to be added to produce a clinker with the required mineral content. The lime content of a limestone deposit is one assessment that needs to be made during an evaluation This author has been asked twice during the pandemic to review data on limestone deposits and their suitability for cement manufacture....

Producing boron cement

24 August 2021, Published under Cement News

The creation of low-energy belite clinker is a specific area of research that aims to reduce CO 2 emissions from the cement manufacturing process. Boron minerals, of which Turkey has 73 per cent of the world’s reserves, are a possible raw material that can be used in the production of belite cements. TÜRKÇIMENTO, the Turkish cement manufacturers’ association has carried out a study into the use of colomonite boron ores to determine their suitability for the production of boron cement. By Se...

Belite size distribution

13 April 2021, Published under Cement News

Belite size is affected by several factors ranging from raw materials, the length of the burning zone, the fuels used in the production process as well as the conditions in the cooling zone.  Figure 1: example of belite crystal size distribution The sizes of belite crystals in Portland cement clinker depend on a number of factors that relate to the raw materials, burning zone length, fuels used and combustion efficiency. Raw materials The relative proportions of alite and ...

Fly ash and pozzolanas

18 January 2021, Published under Cement News

The drive for alternative raw materials has put the spotlight on fly ash and pozzolanas. However, their use in cement has been around for some time. This month Arthur Harrisson looks at their origin and performance in cement. Pumice rock A pozzolana is a material which, when mixed with a hydraulic cement, will react with the lime from the cement and water to produce cementitious hydration products of its own. The most familiar types of pozzolanic materials in common use are low-...

Process, mineralogy and cement quality

08 December 2020, Published under Cement News

This month Arthur Harrisson looks at the relationship between temperature differences in the clinker manufacturing process, the composition of clinker produced and the quality of the final cement. Figure 1: variation of iron oxide and alumina in alite with clinker exit temperatures In a project to explore the influence of different temperature profiles on clinker characteristics, a range of commonly available measurements relating to the clinker manufacturing process were matche...

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...