Solidia Technologies' chemistry could make concrete almost benign.

The making of concrete is responsible for as much as 8 percent of annual CO2 emissions; we have called it the most destructive material on earth. The manufacturers know this is a problem and have been looking for ways to reduce the footprint before a serious price on carbon is slapped on it, and are evidently making some progress.

Carbon emissions come from two sources; traditionally, about half comes from the heating of the kiln, and about half from the chemical reaction that makes cement out of calcium carbonate. LafargeHolcim, the world's largest cement company, has been trying to reduce the footprint of concrete for some time, although we previously noted that they are having some trouble selling it.

That may change; according to Kim Slowey at Construction Dive, LafargeHolcim is going to be selling reduced CO2 cement for the precast industry in the US. It uses technology from Solidia Technologies:

© Making the block/ Mark Scantlebury The product is the result of a six-year collaboration between LaFargeHolcim and Solidia and uses a special binder — produced at lower temperatures — and patented curing process that uses CO2 rather than water. By adding and absorbing CO2, Solidia Concrete reaches strength in less than 24 hours unlike precast concrete made with Portland cement, which takes 28 days to reach strength. Solidia reduces the overall carbon footprint in precast concrete by 70%. In addition, the new product reduces the cement plant’s carbon emissions by up to 40%.

This concrete can be made in a conventional cement kiln with the heat turned down, so it works within the existing systems of production. According to Kevin Ryan in Inc, the process subs out some of the traditionally used limestone for a synthetic version of the mineral wollastonite.

Akshat Rathi wrote a long article for Quartz explaining a bit of the chemistry; it is fascinating stuff. "Wollastonite’s chemistry is such that it would not produce any emissions when it is made to produce cement, but it would, like normal cement, absorb some CO2 when it gets cured as concrete." It's being used for precast concrete because it actually gets cured in a CO2 filled room, and cures very fast so it probably needs controlled conditions.

© Housing and offices can be built out of hollow core slabs/ Thomas Moore

We don't usually say nice things about concrete, and are downright nasty about the Concrete Masonry people and their marketing campaigns against wood construction. But if they can squeeze 70 percent of the CO2 out of precast concrete, I would have to change my tune a bit. Now if only there was a big honking carbon tax that would light a fire under the industry to actually change; otherwise the transition will take forever.

More in the LafargeHolcim press release.

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