As materials they are massively more expensive than carbon steel and first cost matters because public infrastructure is financed with bonds and financial markets dictate bond terms of 30-40 years.
To put it another way, any belief that construction markets are inefficient is statistically a dunning-kruger to too many sigmas. Construction goes back at least as far as anything we call as civilization.
We've made it very hard to build because we really don't want to build. Homeowners are mostly interested in protecting their investment which means keeping housing demand high.
Or use well paid skilled labor and machines?
Isn't that ultimately an economic question - increase the supply and the cost drops, increasing the number of projects where the labor cost effective but driving down wages?
If the US did have much more immigration of unskilled contruction labor, but they unionized, keeping their wages higher, would that have the same result? That is, is your argument more than, effectively, exploiting labor?
Money makes construction easier. For example it facilitates hiring skilled labor (or pays for stainless steel rebar).
The US housing market is shaped by two facts.
1. Housing is just about the “lowest and worst” [1] way to realize returns on real-estate.
2. It is about as hard (and often harder) to build inexpensive housing as expensive housing.
They are so much more expensive than ordinary carbon steel rebar to be unicorn poop rare.
If there is a break in the finish, it is as susceptible to corrosion as carbon steel. This means every step requires special handling and rigorous inspection. It cannot be field fabricated with a hand bender if a stirrup is missing or damaged. Tying and placement has to be done with unusual care to avoid damage (and again non-standard level of inspection).
Galvanizing and epoxy coating are long lead time and require prefabrication (bending). So you are shipping, handling and receiving bespoke space filling shapes instead of commodity straight bars to specialty job shops with limited capacity and well booked dance cards.
At every step, everyone has to price their work against all that complexity, uncertainty and potential for delays.
Epoxy coated rebar turned out to have much poorer efficacy than originally expected as you noted but the same is not true of galvanizing which is a much more durable coating.
Talk to your architect…if I were still practicing and cost was no object, I would probably recommend epoxy coated and 6kpsi concrete and a specialty contractor [1]. I would not recommend someone’s theory over technologies with track records.
[1] And require a percentage of construction cost contract.
If the bond breaks in the end product, the building falls down as the carbon steel inner core slides out of the stainless coating.
How is that solved?
Quick!!!
Regular steel can also be protected from corrosion using paint, zinc coating, cathodic protection, etc.
Engineering is always an exercise in trade-offs. And it's almost always better to build four bridges that can stand for 100 years, instead of one bridge that can stand for 500 years.
Coatings, inhibitors, and additional barriers to water/moisture intrusion help too.
So it's like galvanizing but with stainless steel. Thing is, stainless steel still rusts; just how much depends on a number of factors. And if you slightly nick the stainless coating to expose the iron rebar, now the whole rebar rusts.
Maybe it will reduce the amount of corrosion, and that's great. But I highly doubt it would double the life of bridges.
Of course in practice if this rebar is used in a bridge you might start to discover other things become the bottleneck, but that remains to be seen.
In Europe there is a startup that tries to combat this with embedded bacteria and limestone plates that are put into the concrete. If the concrete gets a crack, the rain gets into the crack and activates the bacteria which is producing limestone to fill in the gaps. [1] [2]
That approach has a much better chance to improve infrastructure lifespan in my opinion, because just putting more steel into it is not something that's affordable. Iron as a resource is way too rare as it is already.
[1] https://www.epo.org/en/news-events/european-inventor-award/m...
Now you need to handle liquids and electricity and your process is not as continuous.
bell-cot•2d ago
One clear downside to stainless-coated rebar: During construction, rebar is very commonly welded. Welding stainless ain't just the same tools & techniques as welding conventional rebar. Plus, welding stainless gets you into chromium hazmat territory.
garbagewoman•5h ago
bagels•4h ago
As the GP points out, the chromium when vaporized is a lot worse for you than what's typically in plain steel.
Not just that, but, if you weld it, now you have exposed the plain steel and have invited rust inside the coating.
garbagewoman•2h ago
dylan604•4h ago
garbagewoman•2h ago
brendoelfrendo•2h ago
garbagewoman•2h ago