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Concrete given extra flexibility

MATERIALS Cutting Edge

ONE OF the big disadvantages of concrete has always been its poor tensile strength.

For years engineers have added reinforcement to the material in an effort to overcome this drawback.

Now researchers at the University of Michigan in the USA have developed a concrete that is 500 times more flexible than traditional concrete and 40 per cent lighter.

A specially coated network of fibres in its engineered cement composites helps the matrix slide along the reinforcing fibres within the cement.

This helps improve the flexibility that causes the brittleness and breakage, according to University of Michigan engineering professor Victor Li.

Scientists design the concrete to ensure its was more flexible as well as reinforcing it with micro-fibres to act as ligaments to bond the material more tightly.

Professor Li said: 'The broad field of micromechanics has tried to understand how composite materials behave.We went one step further and used the understanding as a material design approach in the development of Engineered Cement Composites.'

The material is due to be trialled on the retrofit of a bridge in Ypsilanti, Michigan, where it will replace the expansion joint and link the adjacent concrete slabs to form a continuous deck.

Professor Li said the University of Michigan holds four patents on ECC technology, with three pending.