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Risks of Using Low-Carbon Cement

Although there is now increased interest in low-carbon cement due to rising global warming concerns, their adoption comes with risks that need to be considered. Learn more in the seventh edition of our construction magazine, Building Sight.

Interest in low-carbon cement is ramping up, with established players and startups joining forces.

In the seventh edition of our construction magazine Building Sight, we look at how the construction industry is tackling environmental issues and aiding countries to reduce emissions and meet ambitious targets.

Portland cement is one of the most manufactured materials in the world. It is also the source of about 8% of the world’s carbon dioxide (CO2) emissions, according to think tank Chatham House.

If the cement industry were a country, it would be the third largest emitter in the world — behind only China and the US.

Although low-carbon cement alternatives have been under development for decades, increased concerns about global warming have ramped up interest over the past 12 months.

Two deals in 2019 signal that mainstream construction sees the value in developing low-carbon technologies.

Bouygues Construction is partnering with Hoffmann Green Cement Technologies to develop Hoffmann’s H-EVA cement, which uses alkaline-activated clay.

Hoffmann says its cement has a carbon footprint 70-80% lower than traditional cement.

Meanwhile, global cement manufacturer LafargeHolcim has joined forces with startup company Solidia Technologies.

Solidia cement hardens by adding CO2 instead of water — a so-called carbon-cured cement — which the company says reduces the overall carbon footprint by up to 70%.

It is already common to find concretes in which around a third of cement is substituted with industrial byproducts, such as ground-granulated blast-furnace slag or pulverized fuel ash, also known as fly ash.

Waste from agricultural processes, such as rice husk ash, are also used in mixes.

The substitutes are often used for technical rather than environmental reasons, but they do reduce carbon emissions.

Novel binders, such as geopolymers or alkali-activated cement, are also used in specialist applications. Designed to partially or fully replace cement in concrete production, they can potentially make the binding element almost carbon-neutral.

To date these alternative concretes have rarely been as cost-effective as regular concrete and face market vagaries.

For example, shortages in supplies of fly ash and slag have hit European cement companies. Since fly ash is a byproduct of coal-burning power stations, shortages are likely to increase as countries move to cleaner energy production.

Different concrete formulations can be difficult from a risk perspective, says Gaurav Kapoor, vice president and national project risk leader of the Construction and Surety Practice at Marsh JLT Specialty in Toronto.

“If the process has not been formally tried and tested within a project, or multiple projects, the insurance market might be hesitant as the properties are still unknown.”

In Canada, losses related to concrete and concrete forming has become more frequent, primarily due to issues including faulty workmanship, incorrect finishing, or ineffective or deficient concrete mixes.

As embodied carbon moves up the agenda for construction companies, more projects will be asked to consider lower-carbon mixes. As with any non-standard concrete mix, it is important to include a robust pre-construction testing regime, and allow sufficient time in the program to accommodate this.

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Reduced carbon footprint of H-EVA cement when compared to traditional cement