Ancient Roman workers who lived in Pompeii before the eruption of Mount Vesuvius in AD 79 used molten iron to repair the city’s streets.
Researchers suggest that iron droplets, spatters, and stains found on newly uncovered roads once buried by the explosion are evidence of ancient street repairs.
The discovery reveals a previously unknown method of ancient Roman street repair and represents ‘the first large-scale attestation of the Roman use of molten iron’.
Molten iron would have filled the holes and ruts and hardened into a smooth surface when poured over it.
Repaving would have been expensive and would have blocked important routes through the city for months at a time, experts say.
The repeated passage of carts on the city’s stone-paved streets eroded away ruts and holes that made travel difficult, say researchers from the University of Massachusetts.
After the molten iron was poured, it filled the holes and hardened as it cooled down but researchers found that sometimes ‘accidentally spilled’ while being carried onto Pompeii’s streets.
Other materials such as stone, ground-up pieces of terracotta and ceramics were also inserted into the holes to help fill them up.
This method of repair was cheaper and faster than repaving a street, the team found.
Professor Eric Poehler, a classics professor at the university who led the study, said it would have posed a problem for the people of Pompeii since some of the city’s many streets could become eroded quickly.
Investigations at Pompeii have shown that particularly high volumes of traffic concentrated in narrow streets could wear down even a stone-paved surface in only a few decades,’ the researchers wrote.
Many of Pompeii’s streets were paved with stone, but archaeologists found that over time, the passage of carts eroded those stones to form deep holes, or ruts.
Repaving streets was an expensive and time-consuming process, historical records and archaeological remains show.
‘One option for repair, complete repaving in stone, was a difficult and expensive endeavor that might block important through-routes in a city for months,’ the paper said.
‘Investigations at Pompeii have shown that particularly high volumes of traffic concentrated in narrow streets could wear down even a stone-paved surface in only a few decades.
The Romans would have needed to heat up iron or iron slag to between 2,012 and 1,100 to 1,600 degrees Celsius (2,912 degrees F) depending on the iron.
The A.D. 79 eruption of Mount Vesuvius left the city buried under volcanic material.
Historians have traditionally dated the disaster to Aug. 24 79 AD, but excavations on the site in southern Italy have unearthed a charcoal inscription written on a wall that includes a date which corresponds to Oct. 17.
The writing came from an area in a house that was apparently being renovated just before the nearby Mount Vesuvius erupted, burying Pompeii under a thick blanket of ash and rock.
The graffiti read: ‘XVI K Nov,’ meaning the 16th day before the calends of November, or October 17 in the modern calendar.
Archeologists found the inscription in a house that was in the process of being renovated at the time of the eruption, so the writing would have probably been covered with plaster shortly.