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Why can’t we use carbon fiber or aluminum or anything that won’t rust?

dTal 5y ago
Cost would be my guess.
toss1 5y ago
We actually can - fiberglass rebar has many advantages over steel, among the first being that it does not corrode and expand. It's also much lighter and easier to transport to and on the worksite. It is starting to see widespread use in the construction industry, but far too slowly. A quick search on "fiberglass rebar" will return many manufacturers and articles.
UI_at_80x24 5y ago
To avoid the problems of rust, epoxy coated steel is often used. It costs more, so in situations where the contract is won by the lowest bidder (unless it is expressly required), you don't get it. So as a result, buildings that could last 200 years start to crumble after 50.
- baybal2 5y ago
  Epoxy coated rebar was a trap, and is now being banned around the world. Paradoxically, the epoxy coat can make corrosion worse than the bare steel, let alone galvanised.
  - ggcdn 5y ago
    Not sure why you're being downvoted, because you're right, atleast on the west coast of north america. My firm hasn't use epoxied rebar since like 1990, and we removed all references to it on our drawings long ago. The coatings were super fragile, and often damaged while being placed in the field. Then someone had to come along with magic paint and touch up all the cracks. But of coarse they would never find 100% of them...
    - throwaway0a5e 5y ago
      He's getting downvoted because more modern versions of epoxy coated rebar are still widely used in new construction. It wasn't the silver bullet for salted roadways it was sold as but it has its place.
      - ggcdn 5y ago
        which regions and industry do you see them used? In west coast buildings, its uncommon.
baybal2 5y ago
> Why can’t we use carbon fiber or aluminum or anything that won’t rust? We can, we do, just steel is super duper cheap, and workable. Ironically, it's China now who leads the world in GFRC (glass fibre reinforced concrete) construction to get those miniscule cost savings on steel (despite it being world's biggest steel producer.) There is also basalt fibre reinforced concrete that is supposed to be superior to glass fibre, and can come in workable varieties (heat it up with a torch, and bend.)
ggcdn 5y ago
One of the big reasons is ductility. We want structures to show signs of distress before failing catastrophically. With ductile reinforcing (steel), the deformation at which failure occurs is easily 5 times larger than the deformation where yielding occurs. Large cracks will open up, it hopefully gets noticed, and there is a chance to intervene. With GF or CF reinforcing, failure is sudden and catastrophic.
lurquer 5y ago
> Why can’t we use... You can. Nobody’s stopping you. Perhaps you meant “they” instead of “we”. Pet peeve. I’ve found when you use the proper pronoun — ‘they’ in this case, unless you make concrete — it focuses your thinking. That is, if you want to know why ‘they’ do something, you’ll naturally ask ‘them’. But, when you use ‘we’, you’re more likely to just imagine your own solution. Nothing personal. ‘We’ is the bane of my existence... In order for this post to be somewhat relevant, I’ll add this... I see corroding rebar as a feature and not a bug; it assists in the natural degradation of concrete and it gives me some comfort to know that the distant future will have no signs of the concrete monstrosities that litter out landscape. Thanks, rebar.
rsync 5y ago
"Why can’t we use carbon fiber or aluminum or anything that won’t rust?" You can. Stainless steel rebar is a thing and would, largely, solve the problem of spalling due to rusting steel reinforcements. As you can imagine, stainless steel rebar adds a significant cost.

dTal 5y ago

Cost would be my guess.

We actually can - fiberglass rebar has many advantages over steel, among the first being that it does not corrode and expand. It's also much lighter and easier to transport to and on the worksite. It is starting to see widespread use in the construction industry, but far too slowly. A quick search on "fiberglass rebar" will return many manufacturers and articles.

UI_at_80x24 5y ago

To avoid the problems of rust, epoxy coated steel is often used. It costs more, so in situations where the contract is won by the lowest bidder (unless it is expressly required), you don't get it. So as a result, buildings that could last 200 years start to crumble after 50.

baybal2 5y ago
Epoxy coated rebar was a trap, and is now being banned around the world. Paradoxically, the epoxy coat can make corrosion worse than the bare steel, let alone galvanised.
- ggcdn 5y ago
  Not sure why you're being downvoted, because you're right, atleast on the west coast of north america. My firm hasn't use epoxied rebar since like 1990, and we removed all references to it on our drawings long ago. The coatings were super fragile, and often damaged while being placed in the field. Then someone had to come along with magic paint and touch up all the cracks. But of coarse they would never find 100% of them...
  - throwaway0a5e 5y ago
    He's getting downvoted because more modern versions of epoxy coated rebar are still widely used in new construction. It wasn't the silver bullet for salted roadways it was sold as but it has its place.
    - ggcdn 5y ago
      which regions and industry do you see them used? In west coast buildings, its uncommon.

baybal2 5y ago

> Why can’t we use carbon fiber or aluminum or anything that won’t rust? We can, we do, just steel is super duper cheap, and workable. Ironically, it's China now who leads the world in GFRC (glass fibre reinforced concrete) construction to get those miniscule cost savings on steel (despite it being world's biggest steel producer.) There is also basalt fibre reinforced concrete that is supposed to be superior to glass fibre, and can come in workable varieties (heat it up with a torch, and bend.)

ggcdn 5y ago

One of the big reasons is ductility. We want structures to show signs of distress before failing catastrophically. With ductile reinforcing (steel), the deformation at which failure occurs is easily 5 times larger than the deformation where yielding occurs. Large cracks will open up, it hopefully gets noticed, and there is a chance to intervene. With GF or CF reinforcing, failure is sudden and catastrophic.

lurquer 5y ago

> Why can’t we use... You can. Nobody’s stopping you. Perhaps you meant “they” instead of “we”. Pet peeve. I’ve found when you use the proper pronoun — ‘they’ in this case, unless you make concrete — it focuses your thinking. That is, if you want to know why ‘they’ do something, you’ll naturally ask ‘them’. But, when you use ‘we’, you’re more likely to just imagine your own solution. Nothing personal. ‘We’ is the bane of my existence... In order for this post to be somewhat relevant, I’ll add this... I see corroding rebar as a feature and not a bug; it assists in the natural degradation of concrete and it gives me some comfort to know that the distant future will have no signs of the concrete monstrosities that litter out landscape. Thanks, rebar.

rsync 5y ago

"Why can’t we use carbon fiber or aluminum or anything that won’t rust?" You can. Stainless steel rebar is a thing and would, largely, solve the problem of spalling due to rusting steel reinforcements. As you can imagine, stainless steel rebar adds a significant cost.