Ancient Romans Used Molten Iron to Repair Streets Before Vesuvius Erupted | Hacker News Reader

Ancient Romans Used Molten Iron to Repair Streets Before Vesuvius Erupted

livescience.com

86 pointsgus_massa32 comments

The joy of not having any infrastructure buried under the streets:

"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,"

"A few decades"

I bet there are not all that many streets in the western world which have been around at all for more than a decade.

Probably more than you expect— here in Los Angeles (not a particularly old city), there's hundreds of asphalt streets that haven't been repaved since the 1930s and 1940s while they've been trapped in a Kafkaesque bureaucratic hell (the city disowned the streets for liability purposes). There's even a short stone street in Pasadena that dates back to 1900 or so. I don't think it's been entirely redone at any point, although you can tell where some of the granite chunks have been replaced.

Don’t forget all the concrete streets in LA! All the streets before a certain vintage were paved with concrete and are mostly intact where they haven’t been covered with asphalt.

Snarky answer: there are plenty around me, and they show it.

Serious answer: the street I grew up on, and most of the rest of the streets in that neighborhood, are 30 years old. They were last paved when I was nine. The ones that are newer were only paved because they were ripped up for utility work. There are plenty of roads in the US much older than a decade.

I'm not sure the road was already there when I was born, no recollection it was ever re-paved until they started to dig for utilities twenty-something years later, with all the trucks that carried stuff to build the beach neighbourhoods.

The difference between the old stuff and the new crap they use to pave it is unbelievable. Two years without repaving and it's full of holes.

There's a street in the American city where I live that's said to be about 400 years old.

http://alloveralbany.com/archive/2018/09/07/maiden-lane-alba...

Plenty of cobbled streets in old European cities, some of them open to vehicle traffic - here in Edinburgh, for instance.

The street I live on has not been repaved in the 22 years I have lived here (much to my chagrin!).

More then a decade? There are quite a few streets that have been around since 2008.

Any reason I can't fill the potholes near me with molten iron other than the city will get mad at me?

Asphalt burns surprisingly easily. So, it would probably ignite, then you would have horrible yellow sulfurous smoke going everywhere.

Steam explosion under the molten iron comes to mind.

I'm actually surprised it wasn't lead given the difficulty of melting iron.

This is so hard-core. I love it.

Surely you meant to say "This is so METAL"…

Surely.

They don't show any large patch filling a rut.

Also, molten iron would have presumably been expensive back then - too expensive to simply pave a large part of the street with.

I don't really see evidence this was street repair as much as "occasionally on the roughest roads some drips of molten iron fell off the back of carts while being transported"

They show a whole segment of street repaired this way.

But, as noted in the article, they didn't just fill holes with iron. They filled them with loose aggregate, and glued it all together and to the road by pouring iron over it.

Transporting molten iron by road (for some reason other than fixing the road) would have been even more silly then than it is now. How many molten-iron trucks have you encountered?

Molten iron is not commonly transported on a truck, but molten aluminum is trucked relatively often, with occasional spills.

https://i.imgur.com/Qkai24I.jpg

And for comparison, here is what happens when a train carrying molten iron spills - http://i.imgur.com/qnHuxET.jpg

edit - I think the tree is doing suprisingly well, considering.

Aluminum melts at 660C where Iron melts at 1,538°C. This makes molten Iron vastly more difficult and dangerous to transport.

Steam explosions like happened in the UK steel yard recently.

But why would someone need to carry molten iron? It is inconvenient and dangerous.

There are "torpedo cars", that transport around 200 tons of molten pig iron by rail. Some are insulated enough to transport iron for over 24 hours. The energy advantage is massive.

I'm pretty sure no one moves large amounts of molten iron today. With ancient technology it would have been impractical even if they wanted to, maybe impossible.

They do it all the time, out of the furnace comes crude iron, which then must be moved to the steelmaking plant. It is cast into bars only at the steel plant. The carbon dissolved in crude iron lowers the melting point substantially, it's around 1200 °C, so you can actually transport it in steel vessels.

Have you seen https://www.quora.com/Why-is-molten-aluminum-transported-by-...? They routinely ship entire trucks full of the stuff from foundries to forges over public highways.

The melting point of aluminum: 660°C

The melting point of iron: 1535°C

It's also much heavier. There aren't even many suitable container materials to store it, let alone ship it safely.

They do and the technology used is a steel tube, lined with bricks.

> occasionally on the roughest roads some drips of molten iron fell off the back of carts while being transported

I agree.

When I studied ancient history (and Pompeii) in school we were taught that the 'ruts' were a feature of Roman roads, not a bug. Carts were specifically designed to have axle width match these ruts, and were consistent throughout the Empire [0]. I think this is a low quality article that misconstrues a research paper as actual fact.

I am going to Pompeii in September so I'll try and have a look at these iron patches anyway.

[0] - https://en.wikipedia.org/wiki/Rut_(roads)

In terms of 'ruts', the horse drawn proto-railway dates back to Corinth half a millennium earlier:

https://en.m.wikipedia.org/wiki/Wagonway#Ancient_systems

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