In particular one about epoxy coated rebar that gives interesting notes about why it has its problems: https://youtu.be/xVDy84rR5Z8
I had a great couple of days learning all about the complexities of concrete through his videos.
https://www.ijser.org/researchpaper/Epoxy-Coated-Versus-Galv... has a lot more, but clearly not a panacea...
[0]https://twitter.com/Paul_Denney/status/1397132479144812544
[1]https://www.punchline-gloucester.com/articles/aanews/glouces...
As an economics exercise, it may also be interesting to price in the cost of dismantling/disposing of construction materials into the initial construction cost. I wonder if doing so will steer materials development away from composites that are difficult to recycle towards something new.
Graphene has its own set of problems. Namely, it can be toxic to humans. [1] And who knows what massive quantities of graphene in concrete will do to an environment 10-20 years after the building's construction. Even demolition with explosives will probably be problematic due to potentially massive clouds of nanoparticles it could create.
Even stainless steel rusts, just more slowly. Roughly 10-100x more slowly, judging by https://www.nrc.gov/docs/ML1124/ML112490377.pdf and https://www.mdpi.com/2076-3417/10/23/8705/pdf.
My understanding that the economics have already really pushed us massively forwards in the past decade or two, that we are far more aggressive about recycling construction aggregate[1].
The article has a nod midway through to these concerns,
> The many alternative materials for concrete reinforcement – such as stainless steel, aluminium bronze and fibre-polymer composites – are not yet widely used. The affordability of plain steel reinforcement is attractive to developers. But many planners and developers fail to consider the extended costs of maintenance, repair or replacement.
This definitely seems like a huge societal blind-side to me. As much as it's an issue of planners and developers, I feel like there's a consumer lack of understanding. The invisible hand can't push effectively here, can't reward the builders doing it right adequately. In part because society is not aware, doesn't know what to ask for, doesn't have standards, doesn't view & comprehend the role of maintenance & ultimately recycling. These are far off things.
As my generation starts to see the limits of sustainability, see where so very many many creations begin to become risks & hazards & losses rather than values, we may develop some sense, but switching over into a fear-based emotional reaction isn't necessarily a great fix. Trying to give us all a picture of the life-cycle, the costs, the trade-offs; that seems like the necessary task. Regulating our ability to see & ascertain.
Hopefully we just get better & better about recycling. It'd be so interesting to see how reinforcements are extracted from construction aggregate today. Stainless steel reinforcement isn't expensive... if you can safely view it not as a sunk construction cost, but as a semi-long term loan for a building. Where-as more advanced materials like fiber-polymer, I tend to imagine, may have wonderful characteristics in use, I also tend to imagine them as likely having less recoverability. Steel: material we know how to re-cast.
https://www.concretenetwork.com/concrete/demolition/urbanite...
It's definitely a case of downcycling, though: there's a lot less we can do with urbanite than with cement and aggregate in their original forms.
https://onlinelibrary.wiley.com/doi/pdf/10.1002/suco.2017001...
Some German researchers seem to think that carbon fiber-reinforced polymer "rebar" could be more durable than steel bars with similar cost and lower weight:
https://www.aboutcivil.org/carbon-reinforced-concrete-buildi...
Unfortunately, the terminology is not well standardized, and when you look up "carbon fiber reinforced concrete", you never know if you're going to get a fiber-reinforced cement composite (incorporating carbon fibers directly into the cement matrix) or a CFRP rebar system. Regardless, there do seem to be some improvements on the horizon.
In first-world countries/states with earthquakes, the answer to this is often yes and yes.
A good article from 2000 in Christchurch discusses the issues: https://www.canterbury.ac.nz/media/documents/event/Hopkins-L...
The article is relevant because Christchurch had a major earthquake in 2011. I know of quite a few older buildings that were retrofitted that did not even need to be demolished (most buildings are designed to just survive a major earthquake, but often they need to be demolished due to damage, similar to writing off cars after accidents).
Christchurch did have regulatory failures because many older buildings were known to be unsafe (e.g. only meeting 10% of current code/regulations), but owners could defer fixing them up to code almost indefinitely. But that regulatory failure is being addressed in other parts of the country e.g. Wellington.
The South Island of New Zealand is overdue for a magnitude 8.2 Earthquake which will devastate many towns on the West Coast, and will affect the whole country indirectly. https://www.stuff.co.nz/the-press/news/90364889/magnitude82-...
You can sometimes see where concrete of a building has been tested for example a circular hole about 10cm across is left where a sample was taken.
If interested, next time you meet a civil engineer or someone working in the relevant department that deals with the building codes will often know relevant details about your location.
The concrete and steel have different thermal expansion meaning that, over time, the concrete is bound to develop cracks if there are any changes in temperature.
Another reason why modern structures crack and disintegrate is because they tend to be built from rather large blocks. Whereas old structures were composed from single bricks or stones. The way these were built meant that the structure would crack in multiple places in a way that would allow the movement to be absorbed and distributed throughout the structure and be more easily repaired. See this guy explain it much better than I could: https://www.youtube.com/watch?v=p5qVxAoKwbE
(That, BTW, is from a channel devoted to concrete made by a civil-engineering academic who specialises in the stuff https://www.youtube.com/channel/UCrvfiHNDS_QI-FgKQSmTITQ )
Construction specs often include “Allowed manufacturers” to limit your choices to certain vendors, which theoretically means you get quality material. For stainless steel, sometimes they’ll specify which alloy you need to use (304L and 316L are the most common) You certainly could submit the specified manufacturer’s product and then switch it out for a cheaper option, but if you’re caught, you could be forced to correct the work with the right material or be financially on the hook for another contractor performing the work. It would be up to someone else to notice that the steel contractor isn’t using the specified material, which may never happen.
The ‘use less of it than needed’ problem would ideally be caught by an inspector, but they certainly aren’t perfect.
Here’s a link to Cleveland Clinic’s electrical spec, if you’re curious how detailed they get: http://portals.clevelandclinic.org/Portals/57/2012_Elec%20Sp...
Japanese loathe “second hand” stuff if they can avoid it. This includes property. The service life for buildings is 47 to 50 years or so, for depreciation purposes.
Totally unrelated, but I love that 1000 year old wooden temples get rebuilt every 20 years or so[2] because of the religious idea of renewal.
[1] https://japanpropertycentral.com/2012/06/what-is-the-lifespa...
That doesn't tell you much: in the US the lifetime of a residential rental building is 27.5 years for depreciation purposes, and 39 for non-residential: https://www.irs.gov/publications/p946
https://knifesteelnerds.com/2019/09/23/nitro-v-its-propertie...
But they all corrode, eventually. If you want a true corrosion-resistant metal that stays (kinda) sharp, look at one of the cobalt alloys like Stellite.
All it takes is for architects and engineers to get their heads around new technologies and start specifying better materials. This wouldn't fully solve the CO2 problem of concrete, but it would reduce it by making each ton of concrete last a lot longer.
[1] https://www.owenscorning.com/en-us/composites/pinkbar-vs-ste...
[2] https://www.tuf-bar.com/5-reasons-why-you-should-use-fibergl...
[3] https://www.globalspec.com/learnmore/building_construction/b...
[4] https://www.forconstructionpros.com/concrete/equipment-produ...
There's epoxy-coated rebar, but that's on the way out. Quebec has already banned it. One scratch, water gets in, and corrosion starts. Also, the epoxy can be damaged by UV, like when there's a stack of rebar out in the sun.
[1] https://www.outokumpu.com/en/products/long-products/rebar
And ‘trust but verify’ is important - there are a lot of assumptions people make about what is actually checked or verified that are, well, just wrong. About a lot of things. And if you can’t find anyone saying it is happening, it very well might not be.
To the prior poster - call the NYC building department. Here is a link to their FAQ/index page and it should be straightforward to find from there. They are the ones responsible for making sure buildings don’t randomly collapse in NYC.
https://www1.nyc.gov/site/buildings/business/inspections.pag...
I work right next to a seven-storey office building in Sydney, that's built almost entirely with engineered timber - https://architectureau.com/articles/australias-first-commerc... - ever bigger and taller such buildings are going up, bit by bit, around the world.
UK also has a history of major failured in construction practices and inspection, where chunks of a new apartment block suddenly collapse like in Ronan Point, or a recently renovated tower block goes up in flames and half of residents die despite them warning about issues for years.
I wish living in first world country guaranteed sensible things are happening, but it doesn't
https://www.theguardian.com/environment/damian-carrington-bl... https://en.wikipedia.org/wiki/Ronan_Point https://en.wikipedia.org/wiki/Grenfell_Tower_fire
https://www.nature.com/news/seawater-is-the-secret-to-long-l...
Sounds like they knew.
"A recent innovation in the Japanese real estate industry to promote home ownership is the creation of a 100-year mortgage term. The home, encumbered by the mortgage, becomes an ancestral property and is passed on from grandparent to grandchild in a multigenerational fashion. We analyze the implications of this innovative practice, contrast it with the conventional 30-year mortgage popular in Western nations and explore its unique benefits and limitations within the Japanese economic and cultural framework." The 100-year Japanese residential mortgage: An examination (1995) (https://www.sciencedirect.com/science/article/abs/pii/106195....)
[1]https://www.thelocal.se/20160324/sweden-limits-mortgage-loan...
False.
Large structural failures can be catastrophic and unexpected.
Buildings can and do collapse quite suddenly. The examples here are not necessarily caused by reinforced concrete failures (though several cases make use of reinforced concrete --- generally other failures lead to the collapse). But the final failure of a system under load and near its structural limits can be quite sudden.
Taiwan bridge: https://youtube.com/watch?v=OSCPUGHUyIs https://youtube.com/watch?v=WqHXMswLwPM
Minnesota I35W bridge collapse: https://youtube.com/watch?v=CMdv2wRaqo4
Jerusalem dance floor: https://youtube.com/watch?v=5UOb7RBWlak
Morandi bridge, Italy: https://youtube.com/watch?v=V479srTBlAk
Hard Rock Hotel New Orleans (under construction): https://youtube.com/watch?v=WC8k5unvyfU
Sampoong Department Store, Korea (visualisation): https://youtube.com/watch?v=aQXTSR9koCg
The Kansas City Hyatt Regency skywalk collapse (1981) would be another instance. I don't believe there's video of the failure itself, though Grady from Practical Engineering has a great explainer of what went wrong: https://youtube.com/watch?v=VnvGwFegbC8