https://www.treehugger.com/sustainable-product-design/lafargeholcim-selling-co2-sucking-cement-precast-reduces-emissions-70-percent.html
[links and images in online article]
LafargeHolcim is selling CO2-sucking cement for precast, reduces
emissions by 70 percent
Lloyd Alter
August 15, 2019
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.
There is so far too little demand for sustainable materials,” said
Jens Diebold, head of sustainability at LafargeHolcim. “I would love to
see more demand from customers for it. There is limited sensitivity for
carbon emissions in the construction of a building.
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:
The first customer will be the Wrightstown, New Jersey, plant of EP
Henry, a national concrete products supplier that participated in
LafargeHolcim's and Solidia's pilot of the product.
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.
"If I have to tell people to go buy some new equipment, a new
kiln," says CEO Tom Schuler, "no one's going to adopt it." Solidia's
manufacturing process can be done in existing facilities and costs about
the same as--and, perhaps soon enough, less than--traditional
cement-making methods.
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.
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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