Background: The global annual cement consumption in 2016 was 4.13 Gt and it is expected to grow to 4.68 Gt/year by 2050 (Schneider, 2019), making it one of the most widely used commodities. Today, the cement industry is the third largest industrial energy consumer and its production accounts for 5-8% of global anthropogenic CO2 emissions (IPCC, 2014; Schneider, 2019). The CO2 emissions from the production process originate as fossil fuels and from the decomposition of limestone. Any attempt to reduce the high CO2 emissions from cement clinker production is constrained by the decomposition of limestone, so the preferred strategy is to replace clinker in cement blends. Even if the global cement industry achieves its own emissions targets, cement-related emissions may contribute an alarming 20% of global carbon emissions by 2050 (Beyond Zero Emissions, 2017). There is a need to reduce CO2 emissions across the cement value chain.
Numerous papers have been published on the chemistry of low emissions cements (Van Deventer et al., 2021). In particular, the use of coal fly ash (FA), ground granulated blast furnace slag (GBS) and calcined clay (CC) as supplementary cementitious materials (SCMs) in blended Portland cement (PC) has been reviewed extensively. Similarly, the use of alkalis to activate precursors, mainly industrial secondary materials, has been researched extensively. There has also been increasing focus on calcined clay limestone cement (LC3) binders to reduce CO2 emissions by replacing 50% cement clinker.
Despite detailed research on the microstructure of such binders and claims that they are durable under aggressive exposure conditions, these binders have not been applied widely. This paper will analyse the reasons for the slow adoption of low-CO2 binders, including supply chain constraints, cement and concrete standards, structural design codes and questions about durability. A pathway will be developed for a new value chain to convert unexploited virgin and secondary materials to cement and concrete with low CO2 emissions.