Secret of sandcastle construction could help revive ancient building technique

June 3rd, 2009 - 4:35 pm ICT by ANI  

Washington, June 3 (ANI): A new research has determined that the secret of a successful sandcastle could aid the revival of an ancient eco-friendly building technique.

The researchers, led by experts at Durham University’s School of Engineering, have carried out a study into the strength of rammed earth, which is growing in popularity as a sustainable building method.

Just as a sandcastle needs a little water to stand up, the Durham engineers found that the strength of rammed earth was heavily dependent on its water content.

Rammed earth is a manufactured material made up of sand, gravel and clay, which is moistened and then compacted between forms to build walls.

Sometimes, stabilizers such as cement are added but the Durham research focused on unstabilised materials.

The research showed that a major component of the strength of rammed earth was due to the small amount of water present.

Small cylindrical samples of rammed earth underwent “triaxial testing”, where external pressures are applied to model behavior of the material in a wall.

The researchers found that the suction created between soil particles at very low water contents was a source of strength in unstabilised rammed earth.

They showed that rammed earth walls left to dry after construction, in a suitable climate, could be expected to dry but not lose all their water.

The small amount of water remaining provided considerable strength over time.

According to the researchers, their work could have implications for the future design of buildings using rammed earth as the link between strength and water content becomes clearer.

There is increasing interest in using the technique as it may help reduce reliance on cement in building materials.

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

As well as informing new build designs, the team hopes their findings could also aid the conservation of ancient rammed earth buildings by putting methods in place to protect against too much water entering a structure, which would reduce its strength.

According to research project leader, Dr Charles Augarde, of Durham University’s School of Engineering, “We know that rammed earth can stand the test of time, but the source of its strength has not been understood properly to date.”

“Our initial tests point to its main source of strength being linked to its water content,” he said.

“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,” he added. (ANI)

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