Ground granulated blast furnace slag

Granulated blastfurnace slag is slightly cementitious on its own but in order to optimise its performance it needs to be ground to a controlled fineness. The grinding process takes account of mean particle size, grading (particle size distribution) and the particle shape in order to ensure that when used in concrete the most benefit is obtained.

There are a number of different methods of grinding granulated blastfurnace slag. Traditionally, standard ball mills have been used but during the last 15 years the use of roller presses and vertical mills has increased. Granulated blastfurnace slag is a very hard material and as a result necessitates the use of high wear resistant materials in the grinding process.
Typically ggbs possesses a specific surface area of 450m2/kg.

Some 2.2 million tonnes of ggbs are produced each year in the UK. The vast majority of this is used as a cementitious addition in both ready mixed and precast concrete although both mortars and grouts benefit from its inclusion. Specialist applications such as soil stabilisation are becoming more widely used. ggbs significantly improves the durability of concrete and other cementitious systems whilst positively contributing to both fresh and hardened properties.

Resistance to sulfate attack (both the traditional type and thaumasite formation) is much increased with a complementary better performance in countering acid attack. Chloride ingress is much reduced. No cases of alkali silica reaction have occurred in ggbs concrete.
Ground granulated blastfurnace slag is a leading material in the sustainability debate. For every tonne used instead of Portland cement there is a saving of 1.5 tonnes of natural material and only one fifteenth of the energy is used. There is a very large saving in carbon dioxide emissions.

The material is covered by a European BS EN standard 15167.

ggbs is produced in five locations in the UK:

• Teesport, Cleveland
• Scunthorpe, North Lincolnshire
• Purfleet, Essex
• Llanwern, nr. Newport, South Wales
• Port Talbot, South Wales
  

ggbs concrete has been used on many high profile structures including:

• Queen Elizabeth II Bridge, Dartford
• Second Severn Crossing
• Manchester Airport Second Runway
• Al-Ml link
• Channel Tunnel Rail Link
• Norfolk and Norwich Hospital
• The Millennium Seed Bank, Royal Botanic Gardens, Wakehurst

And many, many more. Indeed approximately 15 million cubic metres of ggbs concrete are produced each year.

For more information contact John Bullock

Please note this website is maintained to provide information and guidance on UK issues, products and applications of those products.