Concrete has become a major focus of green building initiatives and research. The manufacture of the material is one of the worst CO2 generating processes in the world, with five to eight percent of manmade CO2 coming from concrete production. MIT researchers have come up with a way to cut those numbers dramatically by making concrete structures last as long as 16,000 years, requiring less of it to be made in the first place.
The discovery centers around creep - the breaking down of concrete, which they've realized is caused by the rearrangement of nano-scale calcium-silicate hydrate (CSH) particles. CSH particles go through two density phases when mixed with water, at first a density of 64 percent and secondly a density of 74 percent. That upward shift in density causes creep.
The researchers have found a way to stop creep by adding silica fumes - a by-product of producing aluminum - to the concrete. This addition accelerates the density phases all the way to 87 percent and could ideally lead to longer lasting and lighter concrete structures.
The MIT team calculates that structures that were built to last 100 years could last 16,000 years with this new process and the 20 billion tons of concrete produced annually could become a dramatically lower number.
via Greentech Media
written by Alternative Green Technologies, Inc, June 19, 2009
written by Fred, June 24, 2009
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