Sweden:HEAVY CONCRETE & BALLAST: High density magnetite improves weight/volume ratio

Following the start-up of new magnetite separation equipment last December, Minelco is now looking to further customize grading of the grains. With its improved ability to tailor magnetite to enhance the properties of high-density concrete, the company is looking to conduct tests with major pipecoaters. Bredero Shaw, Eupec, and EB-pipe coating use its products. Offshore applications include the Ekofisk II, Armada, and Interconnector pipelines off northwest Europe.

Minelco's range of iron ore and iron oxide products is based on the mining operations carried out by parent company LKAB in Kiruna and Malmberget in northern Sweden.

"There is no lack of material," said sales manager Lars Vikström, as Kiruna is the world's largest underground iron ore mine.

Magnetite, a natural iron oxide, is non-porous. It exhibits a high density ranging from 4.7 to 5.1 metric tons/cu m. The black oxide, which is pure with a low level of inclusions, has paramagnetic properties. While it does not have a magnetic field, a magnet will stick to it in the same way that a magnet will to carbon steel. The particles range from 30 mm to powder fineness. The higher the required density, the smaller the grains, as only magnetite remains in the finest form – rocks are filtered out.

Magnetite was used for the South Arne field's production platform in the North Sea.Click here to enlarge image

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"Everything below the sea surface is a potential application for magnetite," Vikström said.

With magnetite, it is possible to make concrete with densities up to 4 metric tons/cu m, about 60% more than standard concrete. In water, the difference is even more pronounced when the high-density concrete is up to 100% heavier. Magnetite's high density results in decreased volume for a given weight or, alternatively, an increased weight per given volume.

70,000 metric tons for South Arne

Magnetite can additionally be used as concrete aggregate or loose ballast, in the manufacture of anchor blocks and breakwaters, and caisson ballasting. Minelco has supplied 70,000 metric tons of magnetite for structural concrete and ballast for Amerada Hess' South Arne platform GBS and 25,000 metric tons for Veba's Hanze platform storage base.

Pipes with heavy concrete coating.Click here to enlarge image

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The material has a 40% higher heat capacity than ordinary concrete and a 40% higher heat conductivity. Magnetite in pipecoating retains heat longer than pipes with other forms of concrete coating. Less "artificial" heating is therefore required because it takes longer for outside temperatures to cool the contents of a pipe.

Minelco can supply magnetite in various grades, down to powder fineness, customized to requirements. It has offices in Sweden, The Netherlands, Germany, UK, and USA.

For more information, contact Lars Vikström, Minelco. Tel: +46 920 381 64, fax: +46 920 190 88, email: [email protected], website: www.minelco.com.