Low-carbon cement goes commercial

A new geopolymer cement is claimed to reduce carbon emissions during manufacture by 80% compared with Portland cement. It has other advantages too

The UK firm behind an innovative low-carbon cement is about to open a production plant capable of producing 200,000 tonnes of the material a year.

Banah UK produces a two-part geopolymer cement, based on a calcined clay, that reduces carbon emissions during manufacture by up to 80% compared with Portland cement.

The factory is currently being commissioned in Coleraine, Northern Ireland. It will supply BanahCEM to third party manufacturers of construction products, such as concretes used in construction.

It is understood that when the facility opens, Banah UK will be the first company to produce commercially available geopolymer cement in large quantities.

Andrew McIntosh, director of R&D at Banah UK, says: ‘We are working with a number of companies to help them develop products for the construction market; some are ready to move into production when the plant is ready. We have a team of five researchers and chemists working on many aspects of this new technology, and we work in close collaboration with a number of universities across Europe.’

Geopolymer cements, also known as alkali activated cements, either incorporate processed geological materials, as BanahCEM does, or industrial byproducts, such as fly ash from coal-fired power stations or blast furnace slag.

BanahCEM is produced by thermally treating an aluminosilicate clay to make it reactive in an alkaline environment. The temperatures involved are much lower than those required to produce cement, resulting in reduced carbon emissions.

‘The amount of CO2 emitted during manufacture of one tonne of Portland cement is typically just under 800kg,’ McIntosh says. ‘By contrast, producing one tonne of BanahCEM solids results in around 200kg of emissions. In addition, 60% fewer virgin raw materials must be extracted from the Earth to produce BanahCEM.'

He says using extracted geological material is preferable to fly ash or blast furnace slag, which are a dwindling resource in Europe, particularly because of competition from the Portland cement industry, where they are used as supplementary cementitious materials.

BanahCEM offers advantages during installation and operation, including rapid strength gain while setting. At 20°C, 50% of 28-day strength is achieved after nine hours, 80% after one day and 95% after seven days. Compressive strengths of up to 130MPa can be achieved and stress/strain relationships are very similar to normal concrete.

When fully cured the product provides greater resistance to sulphates, abrasion, acid and fire, says the firm. Prices are similar to those of other specialist cements. ‘Geopolymers are not intended to replace Portland cement in low-cost and commodity applications, it is another tool in the cement tool box that addresses the limitations of Portland cement,’ says McIntosh. ‘However, as the size of geopolymer cement plants increases and alternative resources are found, costs will come down.’