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?
In other words if there is a lot of work for untrained workers, it is a poorly run construction site. In a well run construction project, trained workers clean up after themselves and installers don’t need additional people holding up heavy objects during placement because they bring proper tools, staff, and falsework with them.
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?
Back in the late 19th / early 20th century we had no restrictions on immigration, minimal state welfare programs, and no minimum wage laws. Huge numbers of people migrated to the US for work, they rapidly built infrastructure and buildings in cities like New York and Chicago. There was high upward social mobility.
All the problems started with minimum wage laws and the welfare state. You can’t have a functioning welfare state with unrestricted immigration. When you restrict immigration you essentially create a black market for below-minimum wage labour. That’s why the US has such a huge number of illegal immigrants: to do the jobs that nobody else wants in construction and agriculture.
Before all this (effectively) regulation and restriction of the labour market, you had the ability for people to learn skilled trades on the job. That was a form of non-monetary compensation that is no longer economically viable due to minimum wage laws. Minimum wage laws set a floor on the amount of productivity a worker must supply before you can hire him.
The other problem we’ve caused with these laws is inflation. The cost of living has skyrocketed. People on minimum wage today are in many ways economically worse off than the migrant workers arriving in droves before minimum wage laws existed!
Values are our goals, the most important things we have. The world certainly isn't limited to things with a scientific definition. (Also, I expect there are plenty of legal and related definitions of labor exploitation.)
> There was high upward social mobility.
You'll need to document some of these claims. Unions started because working conditions and pay were awful; people were widely exploited - including injured, cheated, etc. - due to their fundamentally weak marketplace position: the owner controls all the jobs, the worker only controls one.
Since unionization, the economy, pay, and working conditions have all boomed. It's hard to argue with the results - the greatest economic performance in history.
Yes, the wealthy and powerful don't get as much of the pie, but the pie is much larger.
> The other problem we’ve caused with these laws is inflation. The cost of living has skyrocketed. People on minimum wage today are in many ways economically worse off than the migrant workers arriving in droves before minimum wage laws existed!
That is a complete falsehood.
> unrestricted immigration
When and where has that happened? Who supports that? It's quite a strawperson.
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.
The lifespan of ordinary rebar in competently cast concrete that is kept dry is very, very long. Maybe if you live right next to the ocean you will have somewhat different considerations, but a quality waterproofing membrane on the outside of your foundation is worthwhile anyway and will help control salt spray as a side benefit.
If you visit, say, an 20 year old, incompetently built structure in a place with real weather (ski lodges are often like this), you can see that the concrete will be in perfectly fine condition, but the structure may smell moldy and interior finishes will be failing.
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.
This is a common claim, but I’m not sure I really believe it. Even for applications that require especially good mechanical characteristics, e.g. tool steels, good stainless alloys can be very good.
I would believe that the stainless alloys that are widely available in large quantities at somewhat reasonable prices for structural use (e.g. 304 and 316 stainless steel) have mediocre mechanical properties.
Tool steels are not stainless, as anyone who forgot to stow away tools properly can confirm.
It's indeed true, but at the same time, non-stainless steels are getting even better.
https://knifesteelnerds.com/2021/10/19/knife-steels-rated-by...
Compare the toughness vs hardness charts for non-stainless and stainless. You’ll find some low alloy non-stainless steels with excellent toughness at a given hardness level, but those have poor wear resistance. Other than that, the charts are just not very different. Note that even some of the very most wear-resistant steels are stainless (but you’ll have to recognize the names or look them up to tell).
Of course, this says nothing about price, availability in large quantities, weldability, or ability to form them in the ways that people building large structures might want.
Stainless steels have lower yield strength compared to carbon steels, meaning that the stainless steels bend under stress more easily. This is not an issue for knives, but it is a big issue for construction materials.
I’m fairly confident that what’s going on here is that no one builds buildings out of high-hardness stainless steel. On the other hand, you can buy excellent construction screws made from 400 series stainless steel if you’re willing to pay for them —- the main problem is that they’re even more expensive than hot-dip-galvanized or fancy coated non-stainless equivalents.
But yeah, I spent some time looking at spec sheets, and it looks like modern stainless steels are actually quite reasonable for construction. But just too expensive for regular construction, especially compared to regular zinc coating.
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.
Cost. This may not be cheap.
Rebar is often part of a structure’s electrical ground. Any protective current supplied might end up exiting through other connected grounds and doing little good.
How do you do this on a bridge? The rebar is one electrode. Where’s the other?
Even if you get it working, I would be a bit nervous about the reaction products. If there’s any current flow, then something is being reduced. If the medium is moist concrete, then it might well be water that gets reduced to hydrogen gas and hydroxide ions. The hydroxide ions may be harmless, but the hydrogen could be problematic.
bell-cot•8mo 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•8mo ago
bagels•8mo 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•8mo ago
bagels•8mo ago
dylan604•8mo ago
garbagewoman•8mo ago
brendoelfrendo•8mo ago
garbagewoman•8mo ago