Woolly researchers reinvent the mudbrick

Researchers have added wool fibres and seaweed alginate to clay to make unfired bricks stronger and more environmentally-friendly.

Mudbrick - a sundried composite material made from a mixture of clay, mud, sand, and water, plus a binding material such as rice husks or straw - dates back thousands of years and is still used in some areas today. Now, a Scottish/Spanish team has produced an updated version using surplus sheep’s wool.

"The objective was to produce bricks reinforced with wool and to obtain a composite that was more sustainable, non-toxic, using abundant local materials, and that would mechanically improve the bricks' strength," said Carmen Galán and Carlos Rivera, researchers at the Schools of Architecture in the Universities of Seville and Strathclyde.

The wool fibres were added to clay using alginate conglomerate, a natural polymer found in the cell walls of seaweed. The mechanical tests carried out showed the compound to be 37% stronger than other bricks made using unfired stabilised earth.

The study, which was recently published in the Journal Construction and Building Materials, was the result of close collaboration between the British and Spanish universities. The clay-based soils were provided by brick manufacturers in Scotland, which was also the source of the wool, since the local textile industry cannot use everything it produces.

"The aim was to produce a material suitable for adverse climatic conditions, such as the specific ones in the United Kingdom," the researchers explained.

They studied the effect of reinforcing various soil types with sheep's wool, and arrived at various conclusions: "These fibres improve the strength of compressed bricks, reduce the formation of fissures and deformities as a result of contraction, reduce drying time and increase the bricks' resistance to flexion."

These kinds of bricks can be manufactured without firing, which contributes to energy savings, they added, suggesting that they could provide "a more sustainable and healthy alternative to conventional building materials such as baked earth bricks and concrete blocks."

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