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Executive summary

Concrete is likely to continue to be the primary volume construction material for most structural applications and its use is likely to grow in the future. Portland cement (PC) and blended PCs are currently the only economic binders for concrete that can match the performance and durability requirements under the wide range of conditions to which concrete is exposed.

Cement manufacture produces large amounts of CO₂ due to energy use and the calcination of CaCO3. Cement manufacture consequently accounts for about 5% of total global anthropogenic CO2 emissions

The pressure to reduce energy consumption and CO₂ emissions during cement manufacture has led the industry to increase the extent to which Portland cement clinker is substituted in conventional cements by other ingredients that are currently approved for standard production, such as ground granulated blastfurnace slag (ggbs), pulverised-fuel ash (pfa or fly ash), natural pozzolans and limestone. However, there have until recently been few serious attempts to develop novel cements based on alternative clinkers with intrinsically lower energy requirements and CO₂ emissions on manufacture than conventional Portland cement clinkers.

This report summarises work on cements based not on C3S (the major phase in PC) but instead on C2S as the major phase, with C4A3$ (calcium sulfoaluminate or ye’elimite) and C4AF (ferrite) as the other two principal phases. It specifically focuses on the LafargeHolcim-patented Aether† cements as an example of this type of cement. These cements can be made from conventional raw materials, in existing industrial installations and offer similar performances to CEM I (ordinary) PC, but with 25–30% lower CO₂ emissions.

The work summarised in this report was funded under the EU LIFE+ and SILC programmes to assess the performance and durability of Aether concrete. It has shown that good-quality concretes can be made using a range of different batches of Aether cement. Specimens have been prepared to allow testing to continue over a number of years. To date, durability data for up to two years have been recorded.