GGBS – or GGBFS, or Ground Granulated Blast-Furnace Slag to give it its full title – is generated as a by-product of the iron and steel-making industries and is an environmentally-friendly alternative to traditional Portland cement when mixing concrete.

But what is GGBS, how is it made, what are its uses and what are its benefits? This month, the team at EasyMix Concrete is taking a look at this little known but highly valuable ingredient in many of our concrete mixes.

GGBS Concrete

What is GGBS concrete?

The iron-making process requires iron ore, limestone and coke to be blasted at 1500°C. As the ore reduces to iron, the remaining materials float on top and get removed in the form of molten slag. If you rapidly quench that molten iron slag in water or steam, you get glassy granules that are ground down to produce a fine powder – GGBS.

This powder is not only extremely cementitious, but also contains high levels of calcium silicate hydrates (CSH) that enhance its strength and durability.

GGBS will usually replace between 30% and 70% of cement in the concrete, although that figure can go up to as high as 85%. It usually replaces cement in exactly the same quantity – i.e. you would replace one ton of Portland cement in the mix with one ton of GGBS. It is usually added at the mixer stage.

What applications are there for GGBS concrete?

There are many areas in which GGBS can be used, including:

  • Foundations
  • Mortar
  • Precast concrete
  • Soil stabilisation
  • Paving
  • And a lot more

What are the benefits of GGBS concrete?

  • Environmental – because GGBS is a by-product of another industry, it requires no new mineral extraction and produces no waste stream. Its production is also estimated to use less than 20% of the energy and produce less than 10% of the CO2 compared to traditional cement. It also has low levels of embodied CO2 and ensures that less industry by-products end up in landfill.
  • Durability – using GGBS instead of Portland cement can increase the life of a building by between 50 and 100 years according to one study (by the Department of Civil Engineering, BITS, Pilani–Hyderabad Campus). GGBS also reduces the potential for thermal cracking, has high resistance to chlorine ingress and performs exceptionally well in aggressive environments.
  • Appearance – using GGBS produces a lighter-coloured concrete than you get when using 100% Portland cement that is not only more aesthetically pleasing, but also produces a smoother finish with less defects thanks to the finer particles.

For fast delivery of the perfect concrete for your project in the London area, EasyMix are the local experts you can count on to get it right every time. With same or next-day delivery and volumetric concrete to ensure you only pay for what you use, it’s no wonder we’re the supplier of choice for so many local construction companies. Call us now to find out more and to order your concrete delivery.