Interesting..should we be recycling, reusing or extending the life of
materials we use..
On 25/5/24 00:01, Stephen Loosley wrote:
`
'Absolute miracle' breakthrough provides recipe for zero-carbon cement
By Michael Irving May 23, 2024
https://newatlas.com/materials/concrete-steel-recycle-cambridge-zero-carbon-cement/
[Photo] “Old concrete can be recycled in furnaces used to recycle steel, in a
new method that drastically reduces the CO2 emissions of both” Cambridge
University
Concrete and steel production are major sources of CO2 emissions, but a new
solution from Cambridge could recycle both at the same time.
Throwing old concrete into steel-processing furnaces not only purifies iron but
produces “reactivated cement” as a byproduct. If done using renewable energy,
the process could make for completely carbon-zero cement.
Concrete is the world’s most used building material, and making it is a
particularly dirty business – concrete production alone is responsible for
about 8% of total global CO2 emissions. Unfortunately it’s not easy to recycle
back into a form that can be used to make new concrete structures.
Scientists have of course been investigating ways to make concrete greener.
That can include changing the recipe to switch out the most polluting
ingredients – specifically limestone – or designing concrete so that it absorbs
more CO2 from the air after it’s laid.
For the new study, Cambridge researchers investigated how waste concrete could
be converted back into clinker, the dry component of cement, ready to be used
again.
“I had a vague idea from previous work that if it were possible to crush old
concrete, taking out the sand and stones, heating the cement would remove the
water, and then it would form clinker again,” said Dr. Cyrille Dunant, first
author of the study.
“A bath of liquid metal would help this chemical reaction along, and an
electric arc furnace, used to recycle steel, felt like a strong possibility. We
had to try.”
An electric arc furnace needs a “flux” material, usually lime, to purify the
steel. This molten rocky substance captures the impurities, then bubbles to the
surface and forms a protective layer that prevents the new pure steel from
becoming exposed to air. At the end of the process, the used flux is discarded
as a waste material.
So for the Cambridge method, the lime flux was swapped out for the recycled
cement paste. And sure enough, not only was it able to purify the steel just
fine, but if the leftover slag is cooled quickly in air, it becomes new
Portland cement. The resulting concrete has similar performance to the original
stuff.
Importantly, the team says this technique doesn’t add major costs to either
concrete or steel production, and significantly reduces CO2 emissions compared
to the usual methods of making both. If the electric arc furnace was powered by
renewable sources, it could essentially make for zero-emission cement.
The technique has already been trialed in furnaces that produce a few dozen
kilograms of cement, and the researchers say the first industrial-scale trials
are underway this month, where it would be producing about 66 tons of cement in
two hours.
The researchers say that the process could scale up to produce one billion tonnes of
"electric cement" by 2050.
"Producing zero emissions cement is an absolute miracle, but we’ve also got to
reduce the amount of cement and concrete we use," said Professor Julian Allwood, who
led the research.
"Concrete is cheap, strong and can be made almost anywhere, but we just use far
too much of it. We could dramatically reduce the amount of concrete we use without
any reduction in safety, but there needs to be political will to make that happen.
"As well as being a breakthrough for the construction industry, we hope that
Cambridge Electric Cement will also be a flag to help the government recognize that the
opportunities for innovation on our journey to zero emissions extend far beyond the
energy sector."
A patent has been filed for the process, as the first step towards
commercialization.
The research was published in the journal Nature. The team describes the work
in the video below.
The world's first process for making zero emissions cement
Source: Cambridge University
--
_______________________________________________
Link mailing list
[email protected]
https://mailman.anu.edu.au/mailman/listinfo/link
--
Marghanita da Cruz
Telephone: 0414-869202
Email: [email protected]
Website: http://ramin.com.au
_______________________________________________
Link mailing list
[email protected]
https://mailman.anu.edu.au/mailman/listinfo/link
