Shape-memory alloys: Filling the gaps

New solids discovered by physicists can strengthen materials, such as concrete, to protect buildings from earthquakes and severe weather.

Shape-memory alloys 'remember' the form of the structure they are built into, and will bend back to their original shape after being placed under stress. The researchers found that SMA wires embedded in concrete bars helped the concrete return to its original form after a load placed on the bar had caused it to crack and bend. However, the cracks in the concrete were left unsealed, reducing the strength and overall safety of the bars.

This problem was solved by using SMA wires in combination with repairing adhesives held inside hollow, brittle fibres, which snap under stress and fill any cracks with glue (pictured). The bars regained their original shape and strength after breaking. When they were reloaded, cracks appeared in other areas but were once again resealed.

Further research is required to investigate how to arrange the wires and adhesive fibres to ensure the technology is used effectively in large-scale construction projects.