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Production of concrete is known to emit a lot of CO2- it contributes to a whopping 8% of the global emissions. However, engineers haven't been able to find a suitable replacement for this building material.
Given the hazardous impact of increasing carbon emissions in the environment, a high demand for carbon-neutral products in the industry has carved a niche market for concrete with a smaller carbon footprint.
Cemex, a UK-based concrete maker, is addressing this demand by going global with its net-zero CO2 concrete to achieve carbon-neutrality in the construction industry as per The CarbonNeutral Protocol.
The preparation of conventional concrete involves heating of limestone to 1300°C, carrying out the conversion of CaCO3 to CaO as a byproduct, and then further heating the CaO to 1450°C to sinter it with other components like gypsum to form clinker, the cement used for binding standard concrete.
However, the new carbon-neutral concrete known as Vertua® involves the substitution of limestone-based clinker with an alkali-activated alumina-silicate polymer matrix. The preparation of this binder doesn't require high temperatures and doesn't emit CO2, dropping its carbon footprint by a staggering 70% compared to conventional concrete.
Though carbon-neutral concrete is more expensive than conventional concrete, the lower carbon emissions are worth bearing the extra cost for some customers. Davidé Zampini, Cemex's R&D head, also says the polymeric binder makes it more resistant to acid and heat than standard concrete, a plus for applications like sewer pipes.
Low-carbon concrete is an emerging market. In September, Amazon invested in CarbonCure Technologies as part of its goal to be carbon-neutral by 2050. CarbonCure injects captured CO2 into wet concrete, which is believed to strengthen the final material. Another company, Solidia, takes a similar approach by using captured CO2 to cure prefabricated concrete blocks and other components.