Page last updated at 11:23 GMT, Wednesday, 3 June 2009 12:23 UK

Sandcastle study for eco-building

The strength of sandcastles is dependent on their water content

The secret of a successful sandcastle could aid the revival of an ancient building technique, according to experts at Durham University.

Researchers have been studying rammed earth, an eco-friendly construction material made from sand, gravel and clay, which is now making a comeback.

It was found that, as with sandcastles, its strength was dependent on having a small water content.

This could have implications on the design of buildings using that method.

Rammed earth was developed in ancient China about 4,000 years ago and spread around the world.

Parts of the Great Wall of China and the Alhambra at Granada in Spain were built using the technique.

There is increasing interest in the process as it could reduce reliance on cement in building materials, which are responsible for 5% of CO2 output.

Part of The Alhambra in Granada, Spain
Rammed earth was used in the construction of the Alhambra in Spain

Rammed earth materials can usually also be sourced locally, reducing transport needs.

The research, funded by the Engineering and Physical Sciences Research Council (EPSRC) and published in the journal Geotechnique, tested small samples.

It was found that the suction created between soil particles at very low water contents was a source of strength.

Dr Charles Augarde, of Durham University's School of Engineering, said: "We know that rammed earth can stand the test of time but the source of its strength has not been understood properly to date.

"Without this understanding we cannot effectively conserve old rammed earth or make economic designs for new build.

"Our initial tests point to its main source of strength being linked to its water content.

"By understanding more about this we can begin to look at the implications for using rammed earth as a green material in the design of new buildings and in the conservation of ancient buildings that were constructed using the technique."

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