Green Technology: New Concrete buildings can last 16,000 years

What is we could use less material, make buildings last longer, and make them more efficient all at once? That’s what new concrete is able to do. Research done at MIT has given more widespread awareness to the power of concrete.

From GreenTech Media:

In a paper published in the Proceedings of the National Academy of Sciences (PNAS) online Early Edition the week of June 15, Professor Franz-Josef Ulm explains that creep is caused by a rearrangement of calcium-silicate-hydrates (CSH) in concrete at the nano scale.

CSH particles typically assemble in two distinct phases when mixed with water. In the first phase, the concrete exhibits a density close to around 64 percent. In the second phase it increases to about 74 percent. The shift in density causes creep.

So how can you stop creep? By adding silica fumes, a waste product of producing aluminum, the density phases can be accelerated and the overall density increased to 87 percent. This third phase, discovered by Ulm, can in turn lead, ideally, to longer lasting or even lighter structures.

The paper also explains, experimentally, that the rate of creep is logarithmic, which means slowing creep increases durability exponentially. Slowing creep with the process outlined in the paper could extend the life of a nuclear waste container built to last 100 years to 16,000 years.

Twenty billion tons of concrete are produced a year, and the total increases 5 percent annually.

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