Carbon emissions from geopolymer cement are a quarter of those from Portland cement.
The world’s first large-scale production plant for an innovative low carbon cement will open in the UK this August.
The factory, located in Coleraine, Northern Ireland, will produce around 200,000 tonnes a year of banahCEM, a two-part geopolymer cement, based on a calcined clay.
Reduced firing temperatures during manufacture mean the material produces around 80% fewer carbon emissions than regular Portland cement, and it requires 60% fewer virgin raw materials to fabricate, according to the firm behind the product, Banah UK.
The production plant is currently being commissioned, and will employ 26 people, and supply to third party manufacturers of construction products, including concretes.
“Banah UK is the first company to produce commercially available geopolymer cement in large quantities,” said Andrew McIntosh, director of R&D at Banah UK.
Geopolymer cements, also known as alkali-activated cements, fall into two categories: some, like banahCEM, use processed raw geological materials; others incorporate industrial byproducts, such as fly ash from coal-fired power stations or ground granulated blast-furnace slag (GGBS) from steel production.
Raw materials are used due to dwindling resources of fly ash and GBBS in Europe and competition for supply from the Portland cement industry, which uses them as supplementary cementitious materials, says Banah UK.
The energy expended during material extraction is easily offset by savings during manufacture, McIntosh told CM: “There is no limestone being converted into calcium oxide and therefore releasing CO2, the temperatures involved are much lower than those required for cement, so massive savings are made in carbon emissions.
“The amount of CO2 emitted during manufacture of one tonne of Portland cement is typically just under 800kg. By contrast, producing one tonne of banahCEM solids results in around 200kg of emissions.”
Geopolymer cements are designed to harden at room temperature and are very resistant to many common concrete durability issues, providing greater resistance to sulfates, abrasion, acid and fire.
A key advantage of banahCEM, over Portland cement, is rapid strength gain after pouring concrete. At 20degC, 50% of 28-day strength is achieved after nine hours, 80% after one day and 95% after seven days, says the firm. Compressive strengths of up to 130MPa can be achieved and stress/strain relationships are very similar to normal concrete.
