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Ultra-Light Concrete: The Answer to a Builder's Prayer?
If it weren't for a chance meeting with a Los Angeles official, Jim Hwang might never have invented what may be the neatest construction material since two-by-fours.
"It was at a mine reclamation conference, and I was very surprised to see him," said Hwang, an associate professor in the mining and materials processing engineering department. "I asked what he was doing there--there are no mines in Los Angeles. He said, 'No, but we have some of the same big problems.'"
In cities such as LA and at old mine sites, these problems take the form of large holes in the ground that need to be filled up. In cities, holes are a side effect of the constant construction and growth of infrastructure, from skyscrapers and parking lots to freeways and sewers. Cities have grown up around old quarries, which supplied the materials for the initial building of the city. But now, they pose a hazard and are a waste of valuable real estate.
To fill these old quarries, cities have been faced with hauling sand and gravel from outlying areas. But when you have to truck tons of fill for more than a few miles--and in Los Angeles, you have to drive a ways to find a quarry--it suddenly becomes very expensive.
"So I said to myself, 'What's the best, cheapest thing to fill holes with? Air! Porous concrete!" Hwang said. "And how do you create that? With aluminum."
Hwang and other researchers in the Institute of Materials Processing had recently discovered a way to recover a residue of powdered aluminum that had previously been discarded during the recycling of bulk aluminum, such as window frames and car parts. At $1 to $2 a pound, powdered aluminum is a valuable commodity, and much more expensive than fill or even concrete.
But powdered aluminum is highly reactive, and a little goes a long way. "When you put aluminum in concrete, it creates gas, like yeast foaming up in dough," Hwang said. "You only have to use from one to twenty pounds for each ton of concrete, depending on the amount of foam you want, and you can at least double the volume." The process halves the amount of concrete needed, cutting the cost of raw materials (including sand and gravel) nearly in half while simultaneously slashing transportation costs.
And it turns out that the foamy concrete is good for more than filling up holes. "It can be a very cool building material," Hwang said. "You can make walls with it, and it provides much better sound and thermal insulation than conventional materials. You can nail it and saw it, too, just like wood."
And for picture-hangers everywhere, it provides an additional blessing. "You hate to put a nail into gypsum wallboard, but you can nail this and it never chips."
Hwang is working with industry to find additional applications for the porous concrete, and would eventually like to see it licensed. The $2 million, four-year project is funded by a $1.2 million grant from the Department of Energy with industry partners providing $800,000.
Ultra-Light Concrete: The Answer to a Builder's Prayer?
If it weren't for a chance meeting with a Los Angeles official, Jim Hwang might never have invented what may be the neatest construction material since two-by-fours.
"It was at a mine reclamation conference, and I was very surprised to see him," said Hwang, an associate professor in the mining and materials processing engineering department. "I asked what he was doing there--there are no mines in Los Angeles. He said, 'No, but we have some of the same big problems.'"
In cities such as LA and at old mine sites, these problems take the form of large holes in the ground that need to be filled up. In cities, holes are a side effect of the constant construction and growth of infrastructure, from skyscrapers and parking lots to freeways and sewers. Cities have grown up around old quarries, which supplied the materials for the initial building of the city. But now, they pose a hazard and are a waste of valuable real estate.
To fill these old quarries, cities have been faced with hauling sand and gravel from outlying areas. But when you have to truck tons of fill for more than a few miles--and in Los Angeles, you have to drive a ways to find a quarry--it suddenly becomes very expensive.
"So I said to myself, 'What's the best, cheapest thing to fill holes with? Air! Porous concrete!" Hwang said. "And how do you create that? With aluminum."
Hwang and other researchers in the Institute of Materials Processing had recently discovered a way to recover a residue of powdered aluminum that had previously been discarded during the recycling of bulk aluminum, such as window frames and car parts. At $1 to $2 a pound, powdered aluminum is a valuable commodity, and much more expensive than fill or even concrete.
But powdered aluminum is highly reactive, and a little goes a long way. "When you put aluminum in concrete, it creates gas, like yeast foaming up in dough," Hwang said. "You only have to use from one to twenty pounds for each ton of concrete, depending on the amount of foam you want, and you can at least double the volume." The process halves the amount of concrete needed, cutting the cost of raw materials (including sand and gravel) nearly in half while simultaneously slashing transportation costs.
And it turns out that the foamy concrete is good for more than filling up holes. "It can be a very cool building material," Hwang said. "You can make walls with it, and it provides much better sound and thermal insulation than conventional materials. You can nail it and saw it, too, just like wood."
And for picture-hangers everywhere, it provides an additional blessing. "You hate to put a nail into gypsum wallboard, but you can nail this and it never chips."
Hwang is working with industry to find additional applications for the porous concrete, and would eventually like to see it licensed. The $2 million, four-year project is funded by a $1.2 million grant from the Department of Energy with industry partners providing $800,000.
Light weight concrete
Date: 2007-08-08 12:33 am (UTC)Re: Light weight concrete
Date: 2007-08-08 12:47 am (UTC)