Any ideas for low carbon bitumen? Post-oil asphalt and roads

[eclipse]

Hi all,
Even though I live in Aussie car-dependent suburbia - I'm a fan of European town plans, the Village Green, local walkable neighbourhoods and shops that serve the local 10 to 15,000 - rather than mega-malls you have to drive to that serve the local 300,000. Why am I raising this? Because if we built New Urbanism we could live on10% of the land and use far less bitumen. Maybe some sort of low-carbon concrete could be substituted?

But what ideas do you have for long term renewable materials to build our roads from - whatever the town plan? What about interstate highways? (And keep in mind I'm a fan of trains and transit, and while not trying to BAN cars - I'm a fan of less cars. Of domesticating them. Of building neighbourhoods that make people happy instead of cars happy.)

[cyrilr]

Low carbon bitumen? That like dry water? Stuff is about as high carbon as it gets.

It is largely used because it is a waste product from oil refining. Not much value. So it is cheap.

It isn't that great, especially in hot climates it crumples up from the heat and contributes to the heat island effect.

Concrete does fine. It is made from natural abundant materials. Limestone, sand and gravel. Won't be running out of those any millenium soon. You just have to find a clean substitute for the heat energy required to make cement and the rebar steel. That is done today with natural gas and coal. It could be done with biogas, hydrogen, high temp nuclear heat. It would be nice to have a lower energy intensity alternative to the rebar steel. Basalt fiber is interesting.

There is also some promising work going on for making clean iron using aqeous electrolysis. Being a low temperature process it uses less energy, and using electricity means all you need is a clean source of electricity, which is much easier than getting "clean coal" for cokes.

[David B. Benson]

Actually we have, in some locations, run out of suitable sand for making concrete.  For it takes beach quality sand; desert sand doesn’t work, having had the rough edges worn off.  This has given rise to sand thieves in some places; Morocco comes to mind.

[eclipse]

Yes - I had heard there were problems with desert sand and beach sand was running low.

We seem to be hitting 'peak sand'. There is actually a "Sand Mafia" in India.
Kids are forced to mine sand from ever deeper river beds.
"Blood sand" seems to be a thing.



It's one reason I'm such a fan of CLT - Cross-Laminated Timber.
It reduces the amount of concrete required.
(As does New Urbanism, but that's a whole other subject.)

[David B. Benson]

Permeable pavements could reduce salmon-killing tire pollutants
2024 Jan 25
Phys.org
techxplore.com/news/2024-01-permeable-pavements-salmon-pollutants.html

Tire particles become trapped in the permable pavements, unfortunately weaker than ordinary bitumen asphalt pavement.