As anyone who's ever visited Italy knows, the ancient Romans were master engineers. Their roads, aqueducts, and temples are still holding up remarkably well despite coming under siege over the centuries by waves of sacking marauders, mobs of tourists, and the occasional earthquake. But it seems the Romans also knew a thing or two about making concrete. While world's 1960s concrete tower blocks and flyovers are crumbling, Roman monuments such as the Pantheon and the Coliseum are still standing.

Now scientists have discovered the secret ingredient behind the longevity of Roman concrete - volcanic ash. The study by the University of California, in Berkeley, found Roman concrete showed no corrosion, with a smooth surface suggesting long-term stability.

Manufacturing modern cement requires heating a mix of limestone and clay at 1,450C. But Roman architectural mortar uses 85 per cent volcanic ash, fresh water and lime, which is cast at a much lower temperature, significantly reducing its carbon footprint.

Now the researchers want to take the Roman techniques and apply them to modern cements.

Dr Marie Jackson said: 'If we can find ways to incorporate a substantial component of volcanic rock in the production of specialty concretes, we could greatly reduce the carbon emissions associated with their production. We could also improve their durability and mechanical resistance over time.'