Carbon curing

The basic building blocks

In its simplest form, cement is combined with sand, water, and aggregate to produce concrete. When the cement and water are mixed, it causes a chemical reaction called hydration, which starts to set and harden the overall mixture.

This process can be affected by a number of factors, from the outside temperature to the amount of cement in the mixture. What is crucial though, is that the concrete retains the right amount of moisture and is kept at the right temperature over a period of time (normally 28 days) to attain its full strength. If it dries out too quickly, the concrete will be significantly weakened - and that's where curing comes in.

Curing is crucial

The curing process not only increases the strength of the concrete, it also makes it more durable, less permeable to water, and more resistant to cracking, freezing, and thawing. 

There are many different curing methods available, from using steam or spraying the surface with a fog mist, through to covering it with moisture-retaining fabric or plastic sheets to prevent moisture loss. We saw the opportunity to innovate a new way of curing concrete using waste CO₂.

Precast was the way forward

The two most common methods of laying concrete are ready-mix and precast. They can both contain the same ingredients, but are produced in very different ways.

Ready-mix is manufactured in a plant and then transferred in cement mixers to the building sites where it can be poured into place. This can have a significant impact on the surrounding environment through increased dust, noise, and transport emissions.

We decided to focus on precast, which utilizes reusable molds to prepare, cast, and cure the concrete in a controlled environment — all in one location, all off-site. The finished products can then be transported to the construction site to be laid in place.

The use of molds reduces any potential errors, and makes it quicker and more efficient to produce large amounts of identical components, such as wall panels, staircases, pipes, and tunnels, which often sit alongside structural steel frames and concrete produced on site.

As well as being able to control the curing environment, precast concrete has several advantages, including lower labor and transport costs, and is a growing industry, valued at around $116 billion in 2019.

Building for the future

Having achieved 20% CO₂ uptake in a lab setting, the potential for our technology is huge once it is commercialized.

In fact, if the global precast concrete industry switched to our carbon curing innovation, we could recycle up to 246  million tons of CO₂ a year - equivalent to removing emissions from 53 million cars.

Our next goal is to increase the amount of CO₂ that can be absorbed into the concrete, as well as further reducing the time it takes to cure it. In addition, there is the opportunity to rethink where the waste CO₂ is sourced from.

Imagine if we used the CO₂ created by the cement production process itself? Then we would be able to reduce the environmental impact of the industry as a whole, and help it transition to a lower-carbon future.