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Slag Types

Slag Types

TRS has specific in-house techniques and skills to identify all of the products below, how best to use them and where not to use them


The processes of iron and steel manufacture give rise to various by-products, some of which are slags. The latter can be described as non-metallic products of metal production and include:

Blast Furnace Slags
Basic Steel Slags
Acid Steel Slags


Blast Furnace Slag
Blast Furnace Slag can be broadly divided into two main categories:

  • 'Basic' iron-making slags which constitute virtually all current production.
  • 'Hematite' blast furnace slag derived from the use of 'hematite' iron ore and generally native to the NW of England.

Blast furnace slags, where properly utilised, can be an excellent source of constructional materials, finding applications in roadstone, concrete aggregate, biological filter media, glass making, cements, etc..

In addition to work on existing and new slag based products, TRS has carried out work to utilise old, stockpiled blast furnace slags. Such work has led to the re-utilisation of several million tonnes of old slags, previously considered unusable.

Basic Steel Slag
Basic Steel Slag is the product of steel making using 'basic' fluxes, i.e. high in Ca0 and/or Mg0. Virtually all modern steel making operations are 'basic' processes, and many old steel making slags also fall into this category. Basic steel slags, both old and new, are under-utilised compared to blast furnace slags. This is partly due to problems of volumetric instability, attributable to the delayed hydration of free lime and/or free magnesia commonly present in these slags. Nonetheless, excellent products an be produced for specific markets in road making applications. However, appropriate informed processing is required to produce satisfactory, high quality products.

Acid Steel Slag
Acid Steel Slags are now relatively rare and are encountered mainly in old deposits in the UK. They contain no free Ca0 or Mg0 and are generally accepted as being volumetrically stable.