As recently as last month, several news articles, including one in Nature, seemed to take a sudden interest in the intense ecological costs of producing concrete. The biggest ecological villain, of course, is the cement in the mix, which requires extremes of heat (and thus energy) for production. It’s also difficult to extract and transport.
So perhaps it’s a coincidence that the Portland Cement Association just released a comprehensive plan titled Roadmap to Carbon Neutrality, that aims to take cement off the ecological hot seat.
I’ve seen these types of grand industry plans come and go, often without the follow-through to claim success after the initial enthusiasm fades. That’s not to undercut the effort, it’s to keep the pressure on, now that an initial plan has been outlined.
Any man-made endeavor that requires energy, resource extraction, and transportation produces pollution. All you can do is try to mitigate those initial effects by using less energy, specifying less CO2 intensive materials, offset them with things like renewable energy production, and, sometime in the (at this point far distant) future, actively sequester the carbon created by the production process.
Not every approach to reducing cement’s heavy CO2 impact is equal, however, and that may be something for PCA to consider. The organization presents the various approaches to reducing the CO2 impacts of cement as a sort of a la carte menu of options. But some ideas floated in the plan, such as emphasizing concrete’s natural tendency to act as a CO2 sink during its lifespan, probably should not be included in the list of actionable ideas.
Concrete does absorb CO2, but that’s been the case for 1,000 years. All we’d be talking about is whether new types of admixtures could increase the absorption rate, which is a valid area of R&D, but maybe not something to focus on.
That being said, I don’t disagree with the “do everything that helps” approach PCA has taken. They’ve acknowledged that reining in concrete’s footprint (with an emphasis on cement) will require changes at every level of the material’s life cycle. From extraction of raw materials to the choice of clinkers and mixing agents, to the suitability of concrete mixes for recycling.
The challenges are many, but not insurmountable. We need greener filler and admixtures, for example, but many specifications, especially on the commercial side, only accept certain additives.
It’s also understandable that building experts like to move slowly on changes to concrete formulation. Durability is key. In Ireland, for example, one company’s use of excessive amounts of mica in the mix for cement blocks has led to thousands of building failures.
It’s hard to disagree with PCA’s assertion that concrete will remain an essential base material for the resilient infrastructure we need to survive Climate Change. We’ll need homes with sturdy foundations that can withstand floods, monster hurricanes, and so on. It’s good to see the cement industry taking steps, however, to address their own significant role in global warming.
Residential builders have a lot more flexibility when selecting concrete options than their commercial counterparts. In the field here are a few ways to reduce concrete impacts immediately.