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  • Transcriber: TED Translators Admin Reviewer: Rhonda Jacobs

  • Concrete is all around us,

  • but most of us don't even notice that it's there.

  • We use concrete to build our roads, buildings, bridges, airports;

  • it's everywhere.

  • The only resource we use more than concrete is water.

  • And with population growth and urbanization,

  • we're going to need concrete more than ever.

  • But there's a problem.

  • Cement's the glue that holds concrete together.

  • And to make cement,

  • you burn limestone with other ingredients in a kiln at very high temperatures.

  • One of the byproducts of that process is carbon dioxide, or CO2.

  • For every ton of cement that's manufactured,

  • almost a ton of CO2 is emitted into the atmosphere.

  • As a result,

  • the cement industry is the second-largest industrial emitter of CO2,

  • responsible for almost eight percent of total global emissions.

  • If we're going to solve global warming,

  • innovation in both cement production and carbon utilization

  • is absolutely necessary.

  • Now, to make concrete, you mix cement with stone, sand, and other ingredients,

  • throw in a bunch of water, and then wait for it to harden or cure.

  • With precast products like pavers and blocks,

  • you might shoot steam into the curing chamber

  • to try to accelerate the curing process.

  • For buildings, roads, and bridges,

  • we pour what's called ready-mix concrete into a mold on the job site

  • and wait for it to cure over time.

  • Now, for over 50 years, scientists believed

  • that if they cured concrete with CO2 instead of water,

  • it would be more durable,

  • but they were hamstrung by Portland cement's chemistry.

  • You see, it likes to react with both water and CO2,

  • and those conflicting chemistries just don't make for very good concrete.

  • So we came up with a new cement chemistry.

  • We use the same equipment and raw materials,

  • but we use less limestone,

  • and we fire the kiln at a lower temperature,

  • resulting in up to a 30 percent reduction in CO2 emissions.

  • Our cement doesn't react with water.

  • We cure our concrete with CO2,

  • and we get that CO2 by capturing waste gas

  • from industrial facilities like ammonia plants or ethanol plants

  • that otherwise would've been released into the atmosphere.

  • During curing, the chemical reaction with our cement breaks apart the CO2,

  • capturing the carbon to make limestone,

  • and that limestone's used to bind the concrete together.

  • Now, if a bridge made out of our concrete were ever demolished,

  • there's no fear of the CO2 being emitted because it doesn't exist any longer.

  • When you combine the emissions reduction during cement production

  • with the CO2 consumption during concrete curing,

  • we reduce cement's carbon footprint by up to 70 percent.

  • And because we don't consume water, we also save trillions of liters of water.

  • Now, convincing a 2,000-year-old industry

  • that hasn't evolved much over the last 200 years,

  • is not easy;

  • but there are lots of new and existing industry players

  • that are attacking that challenge.

  • Our strategy is to ease adoption

  • by seeking solutions that go beyond just sustainability.

  • We use the same processes, raw material, and equipment

  • that's used to make traditional concrete,

  • but our new cement makes concrete cured with CO2

  • that is stronger, more durable, lighter in color,

  • and it cures in 24 hours instead of 28 days.

  • Our new technology for ready-mix

  • is in testing and infrastructure applications,

  • and we've pushed our research even further

  • to develop a concrete that may become a carbon sink.

  • That means that we will consume more CO2 than is emitted during cement production.

  • Since we can't use CO2 gas at a construction site,

  • we knew we had to deliver it to our concrete

  • in either a solid or liquid form.

  • So we've been partnering with companies that are taking waste CO2

  • and transforming it into a useful family of chemicals

  • like oxalic acid or citric acid,

  • the same one you use in orange juice.

  • When that acid reacts with our cement,

  • we can pack in as much as four times more carbon into the concrete,

  • making it carbon negative.

  • That means that for a one-kilometer road section, we would consume more CO2

  • than almost a 100,000 trees do during one year.

  • So thanks to chemistry and waste CO2,

  • we're trying to convert the concrete industry,

  • the second-most-used material on the planet,

  • into a carbon sink for the planet.

  • Thank you.

Transcriber: TED Translators Admin Reviewer: Rhonda Jacobs

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B1 TED co2 concrete cement carbon curing

How we could make carbon-negative concrete | Tom Schuler

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    林宜悉 posted on 2021/01/05
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