A research project in Northern Ireland is exploring how adding recycled carbon – in its purest form – could make better concrete
McKenna’s team, based at Enniskillen’s South West College, found that turning the waste into charcoal made it a purer, more consistent product. “Charcoal is created by pyrolysis: heating the waste in the absence of oxygen. This drives off a lot of the volatile impurities and leaves us with mainly carbon.” This process is already used in agriculture to make the soil improver, biochar.
“Unfortunately, our waste wood charcoal is still not pure enough for agricultural purposes. But just as biochar’s unique properties can enhance soil, we believe it could also be a useful additive to concrete.” McKenna is now investigating charcoal’s use as a cement substitute, a hydration controller, and as a volume replacement material. “Of course, using charcoal is a way of storing carbon for the long term and reducing concrete’s carbon footprint. But we are not out simply to maximise carbon sequestration. We want to take an unbiased look at exactly how charcoal can affect concrete in both the curing process and the finished product.
The more we know, the more applications will emerge.” Early research has involved grinding down the charcoal to a fine powder with particles about 50 microns across – a size comparable to cement powder. “As a cement substitute, we are probably looking at just 1 2%,” says McKenna, “but the effects on hydration are interesting. Essentially the charcoal acts as a micro-sponge, initially absorbing moisture and tending to speed up the curing process. This has the potential to deliver buildability benefits on site, or speed up precast production.”
Interview by Tony Whitehead
出版于CQ Autumn 2022