By John Dodge
Posting in Education
The time for greener concrete has arrived and the industry along with researchers at MIT are tackling the problem. by John Dodge
MIT Prof. Franz-Josef Ulm is obsessed with concrete and how to make it greener. "Concrete isn't green. It's gray, isn't it?" he jokes.
But he's solidly behind the reinvention of this backbone material found in structures and roadways that happens to contribute up to five per cent of the world's carbon emissions. To fix it, he has put together the "liquid stone" team comprised of engineers, urban planners, architects, economists and physicists at MIT.
Led by Prof. Ulm, the team in concert with the Portland Cement Association and the Ready Mixed Concrete Research & Education Foundation will try to come up with a greener concrete. More specifically, that means reducing the carbon emissions in concrete production by 83 per cent over the next 40 years.
Enter the Concrete Sustainability Hub, a $10 million effort that has the weighty task of examining every aspect of concrete to make it more sustainable. "We will take a holistic approach to its sustainability which means three things: reducing its environment footprint, social progress and economic progress," he said.
Let's first look at the problem and it's a big one - 25 billion tons of concrete are produced annually on a worldwide basis versus 3.3 billion tons of lumber.
The production of concrete emits carbon dioxide (CO2) in two ways. Cement forms the glue in concrete and is made from limestone. However, limestone isn't cement until the CO2 is baked out, a process that makes up half of concrete's carbon emissions.
"With cement and water, you get a solid and that is the secret of cement and concrete. Mixing water with limestone does not produce a solid," he says. Cement binds together the ingredients of concrete which also includes sand and stone.
The other 50 per cent of carbon emissions comes from fossil fuels used to heat the limestone up to 1,300 degrees Celsius. If you ever driven by an operating concrete plant, there will invariably be a tall stack with smoke pouring out.
The major push will be to come up with a stronger product so walls and floors, for instance, can be thinner.
"We have decoded the DNA of concrete and will start modifying the material like they do in biotech with the genome. We are going from the fundamental atomic scale of cement all the way to structural aspects," he said.
Then, they will examine the impact of thinners walls, for example, on CO2 emissions and thermal characteristics if building. They will also determine how much concrete is recycled or ends up in landfills. To fulfill the economic aspects, they will study how greener concrete and its surrounding infrastructure will create new jobs and skills.
In the end, the three underlying tenets of sustainability will be addressed. "How would progress in concrete science increase employment?" poses Prof. Ulm.
Will concrete be radically modified or even replaced? It's hard (pun intended) to replace something so strong, durable and time tested, but a new concrete could be created from the millions of tons of fly ash from coal waste.
"Fly ash has a component of aluminum that allows for denser concrete," he explains, adding that fly ash's contaminants would have to be contained in a concrete end product (Sixty Minutes aired a segment Sunday on the fly ash disposal problems and its toxicity on which the EPA will soon rule.)
"These are the typical questions we will try to take on," he says.
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Oct 6, 2009