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A Mix For All Seasons

A new concrete mix will prevent buildings from fragmenting in a bomb blast.

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One of the main challenges faced by engineers is the preparation needed to prevent tragedy. Many disasters are predictable, including earthquakes and hurricanes. The trouble comes when a builder’s job involves predicting – or accounting for – the unpredictable. It is more difficult to predict a terror attack on a building than an earthquake or a hurricane. Engineers and researchers are kept busy as a result in developing brand new, innovative responses to disaster.

A team of top scholars from Canada, India and the United Kingdom are developing concrete whose design helps prevent injuries by reducing fragmentation. 

According to the study, “the majority of injuries caused from bomb attacks are a result of fragmented building components energized by the blast wave.” For this reason, the study strove to reduce fragmentation in concrete used to make buildings. The new mix, which uses 3D steel fibres, is nearly 80% better than 2D-steel-reinforced concrete at withstanding sudden shock waves, holding together and withstanding fragmentation.

One of the researchers, Alan Richardson, chairman of the Northern Region of the Concrete Society, notes that the use of 2D steel rods, spread randomly throughout the mix, makes the concrete less stable. 2D steel rods have traditionally served to reinforce concrete structures but may not withstand stress from all directions. Many of the injuries caused by the 2004 Madrid bombs, for example, were the result of flying shrapnel, shards and fragments. According to Richardson, this may be because 2D rods cause concrete to fragment in an explosion.

The use of 3D rods, which offer multi-directional reinforcement, increases both the post-crack toughness and the flexural strength of concrete. ‘Flexural strength’ refers to the stress needed to make a material like concrete give way.

As well as the prevention of injuries, the applications of this mix are numerous. Its uses include reinforcement of sea defenses, bridges, buildings and motorway barriers.

Steel rods used in the production are made in India and then shipped to Northumbria, where the concrete is mixed, set and tested.

Learn more about this project at R & D Magazine.

Image courtesy of Northumbria University

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