Show Details

Rammed Earth

July 16, 2009

The right amount of water can make a green building material super-sturdy.

Transcript

BOB HIRSHON (host):
The sandcastle principle. I’m Bob Hirshon and this is Science Update.

To make a perfect sandcastle, you need just the right amount of water. It turns out the same is true for an ancient building material that’s making a comeback. It’s called rammed earth, and it’s a compacted mixture of sand, clay, gravel, and water. Civil engineer Charles Augarde of Durham University in England notes that unlike a sandcastle, rammed earth never totally dries out.

CHARLES AUGARDE (Durham University, England):
Even though we think of sand particles as very small; they’re not really very small when we compare them to clay particles, which are so small you can’t see them or feel them in your hands.

HIRSHON:
Those dense particles trap water inside. Now, Augarde and his colleagues have found that rammed earth’s strength depends directly on its water content. That’s useful information for green-minded engineers, who see rammed earth as a climate-friendly alternative to concrete. I’m Bob Hirshon for AAAS, the Science Society.