Stonehenge inspires

Stonehenge has survived largely because it was over-engineered by its prehistoric designers. Modern builders do not have the luxury of such leeway and that is why buildings and structures made of modern materials can deteriorate in far less time than 4,000 years. They age and need help and Dr Paolo Casadei aims to prove that new techniques can do the job.

He believes that reinforced concrete can be repaired by the careful addition of prestressed fibre-reinforced polymers (FRP). Steel is sometimes used for this, by bonding plates to the surface of the structure. However, it does have problems as, when the steel corrodes, the bond gets weaker. Other FRP solutions have been tried but none has exploited the material's high-tensile properties.

Casadei believes prestressed FRP systems can provide several advantages, besides the direct economic benefit of fully employing the high-tensile strength of the materials. These include: increasing live load capacity; reducing dead load deflections; reducing crack widths and delaying the onset of cracking; reducing serviceability problems such as excessive deflection, cracking of the concrete and tensile steel stresses at serviceability; and improving fatigue strength by reducing tensile steel stresses.