木炭混凝土

A research project in Northern Ireland is exploring how adding recycled carbon – in its purest form – could make better concrete

一眼任何跳过,您可能会看到大量的木材废物:从胶合板和旧窗框到芯片板和MDF的所有内容。回收或重用是棘手的东西,但是北爱尔兰的一个研究项目正在研究如何在混凝土中使用杂色的废物收集。Crest Center工业发展助理SeánMckenna说:“建筑和制造产生了许多木材废物,但其中大部分被胶水,油漆或树脂污染。”“我们的研究最初集中在如何使其更加重复使用。”

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.”

违反直觉的是,木炭的海绵状特性也可以减少混凝土收缩:“这通常是因为水分在倒入后太快而逃脱了混凝土,”麦肯纳说。“但是我们认为木炭可以通过缓冲该过程来提供帮助。尽管木炭起初会吸收水分,但似乎有更多的水可用于固化的后期阶段,因为它存储在木炭的高表面积内。”最后,麦肯纳说,木炭可以使混凝土更加防水:“碳是一个了不起的元素。这是生命的基础,被称为宇宙乐高。在混凝土中,

我们发现它的形状倾向于填补微观结构内的空白,从而有可能提高不渗透性。”对于从肮脏的木材中得出的材料来说,这是一系列令人印象深刻的品质,也是建筑师的麦肯纳(McKenna)渴望与生产商或制造商共同开发研究。

Interview by Tony Whitehead

出版于CQ Autumn 2022