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Why does it have to be either or? Aren't there plenty of use cases for the concrete with less compressive strength? Stuff like floors and walls of smaller buildings could be perfectly fine with the 25 MPa, couldn't they? Patios? Foundations of smaller buildings?

If there's a good amount of stuff that doesn't need the higher compressive strengths, I'd think there could be some decent potential to offset with this stuff. Applications that really need higher strength wouldn't need to use this carbonized stuff.

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There's need, and there's expect. Unless you expect every homeowner or other property owner to do expensive and destructive testing prior to a reconfiguration, remodel, or bringing in heavy semi-stationary loads onto their property, it's somewhat critical that concrete behave like concrete regardless of its initial use case.

A simple example is in my previous home when I had a section of the master bedroom closet partially walled around a Class C TL-30 rated firesafe, and the room partially reconstructed with ballistic armor in the walls and a vault door, to turn it into a safe room for valuables + home protection. The safe had a weight of nearly 9000 pounds in a footprint of 64 by 30 inches on the floor. I was only able to do this because the house was a slab on grade construction and we knew the footing depth and slab thickness of the concrete would handle the weight.

If this had been some sort of "eco concrete" it would have cracked and eventually failed under that weight, and we would not have known this because the slab thickness would have been the same.

P.S.: Since everyone always asks because it's hard to find actual safes (most "safes" are garbage RSCs), it was custom built by a local safe-maker and expect to pay $$$$$. The safe I had installed was $35k, and that didn't include the room tearout/rebuild or the vault door, just the freestanding safe that went into the room.

> A simple example is in my previous home when I had a section of the master bedroom closet partially walled around a Class C TL-30 rated safe, and the room partially reconstructed with ballistic armor in the walls and a vault door, to turn it into a safe room for valuables + home protection.

But... why? This does not seem like a typical use case.

It's pretty much a rite of passage as internet millionaires to have a safe room with 9,000 lb safes isn't it? Who doesn't have a house with a ballistic safe room? I'm just trying to put the helicopter landing pad on my house and the damn HOA won't pass my building plans. I think I'm going to have to buy a bunch more houses so I can get more votes. #noNimbys

Why can't people just do exclusively normal things in their home, like eat corn flakes and consume popular media?

You're free to churn butter by hand using a toothpick in the comfort and privacy of your own home, but I wouldn't take complaints about toothpick integrity from someone doing that seriously.

There are much better arguments against shitty, compromised concrete than 'I need to park a semi-truck in my bedroom closet.'

There are much better arguments than "I want to blow up a bomb in my house" as well. Oh, and there are better arguments than "I want to dig the house out of the ground and drop it from a great height".

One example of a reasonable argument is: "I want to put a very heavy safe on the floor, which works fine when it's normal concrete".

Don't forget the other reasonable part, testing that 50 caliber machine guns can't penetrate the safety of your home walls. That's pretty normal too, right?

To be fair, someone building a panic room/closet for personal protection makes a hell of a lot more sense than buying a gun for a similar purpose.

Unless your threat vector is 'A cartel/the Mossad/the FBI really, really wants you dead', a cellphone and a room with no windows and a heavy door that locks from the inside will solve 99.9% of that problem, without all the problems that guns bring.

You've clearly never been to Compton

The public good of reducing CO2 emissions is a higher priority. By the way I have a safe, too. It’s 30 lbs and fireproof (supposedly).

Well, it is not really atypical to have one of the thousands of possible atypical use cases in any home.

I get your point that it’s convenient to be able to blindly trust a slab, but in older houses you often have slabs that are too cracked, have settling underneath, or are otherwise unsure or suspect enough to blindly assume the “concrete will behave like concrete.” In those cases it’s pretty straight forward to just cut/demo out section of the slab, dig a new footing or prep for new slab in that area, and then reinforce as spec’d for the intended load. E.g. car lift in older garage. Even w/ new(er) construction I wouldn’t be trusting it to handle any sort of outlier use case without testing, or at least having the original blueprints w/ specs for the slab.

I’d be a little cautious dropping in several tons of mass over a few inches of concrete unless I knew it was reinforced (depending on age of house), in good shape, and soil conditions - even for slab on grade. Pour conditions are highly variable too - how do you know the contractor wasn’t drunk that day.

I suppose the point is that it doesn’t matter what concrete was used as long as you knew how it was actually built and current conditions of the foundation (and below the foundation for that matter).

ok, then color-code the pour. Just toss a tint into the mixer and all you need to to in case of later modifications is drill a pilot hole and look at the color of the dust.

stupid question: why keep such valuable items at home in the first place? if they are replaceable, you can just insure them. If they are not, they are better stored somewhere else, no?

By having such high valuables at home, aren't you putting your family at risk?

Also, why talk about these things on the internet? Isn't that painting a target on your back too?

I understand the safe room, just not the safe.

> why keep such valuable items at home in the first place? if they are replaceable, you can just insure them. If they are not, they are better stored somewhere else, no?

You would think, unfortunately banks have done a great sleight of hand in the US limiting their liability related to safe deposit boxes /and/ safe deposit boxes available to rent are nearly impossible to find. Nearly every bank branch in any major metro will have a waiting list that is years out to get a box.

What's so valuable? Well, basically the same stuff most people keep in a random desk/dresser drawer, but ought to have in a safe: Paperwork mostly, guns, jewelry. It's not like I'm storing anything worth tons and tons of money, but the insurance break on getting everything fully covered when you have that sort of safe is significant, and it's one-time up front expense to ensure you can properly store things like paperwork, guns, and jewelry which is easily worth tens of thousands of dollars anyway.

The only difference between me and every other random joe that buys a gun safe at bass pro/cabela's, is that I know what an /actual/ safe is, and I went about acquiring one rather than the cheap RSC you can bypass with a pry bar and a hammer or a sawzall.

> By having such high valuables at home, aren't you putting your family at risk?

Many people have things at home equally valuable, they just don't bother actually doing anything to protect them. I don't think doing the work to protect them adds any additional risk.

> Also, why talk about these things on the internet? Isn't that painting a target on your back too?

Sure, I suppose so. That's true of so many things. I think it's important to be transparent with information though and then mitigate or hedge any risks that come with it. For instance, in my case, I'm nearly always home, I'm always armed, and my valuables are well protected. If someone were to find out and decide they wanted to rob me, the most likely outcome is they'd be leaving in a body bag, so they're unlikely to think that is a wise idea.

NYT article describing your exact point on the perils of bank safe deposit boxes

https://web.archive.org/web/20230108123245/https://www.nytim...

Edit: HN discussion https://news.ycombinator.com/item?id=20545276

To expand on this, generally if you have an itemized insurance rider for personal property on your homeowner's insurance or renter's insurance, everything is covered, but anything stored offsite such as a storage unit or safe deposit box is only insured to a small percentage (10% or less usually) of the total general unscheduled property coverage and cannot be covered with a scheduled/itemized rider. This combined with the shady way banks treat safe deposit boxes means that ironically in the case of /anything/ short of a flood or fire, you are better off having a safe at home vs a safe deposit box, even for insurables like guns/jewelry/collectibles.

A safe deposit box /might/ be marginally better for backup drives and paperwork simply because it's offsite, but a 3-2-1 (one is none, 2 is one) policy/process is better. This really sucks for paperwork because the government is stupid and usually only the actual original matters (e.g. signed marriage license or birth certificate) and certified copies aren't sufficient.

I HIGHLY recommend anyone who wants to be an actual responsible adult to buy a /real/ safe for their home and stick the things that will utterly destroy their life if they're lost/stolen/destroyed into that safe, and keep a spare key/combo to it with whoever is the executor of their will/estate. Nearly every person in America over the age of 30 has tens of thousands of dollars in valuables worth protecting, they just may not think of it as that. It's something like the deed to your house & the associated title and mortgage paperwork, your car titles, insurance policy information for valuables, your marriage license, your passport & birth certificate or other identifying documents, etc. This stuff is absolutely worth protecting, and the dinky "document safe" for $30 at Walmart isn't going to do jack shit.

EDIT: Edit to add that a real safe doesn't have to be $35k. I bought a huge safe when I did it. If you want a small fire-rated Class B TL-30 safe that weighs in the neighborhood of 500-800 pounds, can hold most things other than rifles/shotguns/long-guns, you can find something decent for less than $5k without much trouble, which is around what it costs for a "nicer" "gun safe" at bass pro anyway.

When you include car titles, something people lose constantly and costs $15 to replace at the DMV... It makes me wonder about all the other things you listed being easy to replace also and you're just trying to explain why you got a safe for paperwork.

My mother guards her social security card and passport like they are the keys to life. She was absolutely shocked that I let a scooter rental shop in Vietnam hold my passport as collateral.

People lose or get robbed of everything important all the time. There's a process for everything. I rather not worry and just live my life and deal with things as they come, not worrying so much.

> People lose or get robbed of everything important all the time. There's a process for everything. I rather not worry and just live my life and deal with things as they come, not worrying so much.

You have a much rosier picture of things than I have. I have had to learn the hard way about some of these things, it sounds like you've been lucky so get to be happy-go-lucky. I hope you continue to have good luck in your life. Car titles are only easy to replace while you retain possession of the vehicle and are the recorded owner in the DMV database.

If someone steals the car + title (which happened to me once when I foolishly did what many people do and left the title in the glove box), they can easily re-register the vehicle to themselves and you have basically no recourse unless you can conclusively prove they forged your signature or fraudulently registered the vehicle. Once the successfully record the title change you are pretty screwed, as the saying goes "possession is 9/10s of the law", and it's sadly pretty true. You'd think reporting a car stolen to the police would block someone re-registering it, but that wasn't the case then. It was over 15 years ago, maybe things are better now as much vehicles are electronically titled, but I'd still recommend not losing it.

Maybe my viewpoint is simply a matter of age. Things are much more electronic now and paperwork is less important because there are electronic records. On the flip side, if the electronic records are wrong, sometimes paperwork is the only thing you have to prove that.

Part of being happy go lucky involves not being totally oblivious. There's a big difference between worrying enough to put your car title inside a $5k safe, and worrying so little you keep it inside the car itself.

> You'd think reporting a car stolen to the police would block someone re-registering it, but that wasn't the case then.

Uh, why would that work? Reporting the car stolen should require proof of ownership to prevent denial of service attacks. Someone cuts you off on the freeway? Report their car stolen.

If you call police and report your car stolen the next day it is stolen - police report will be your argument and you not only will get your car back, also whoever re-registered vehicle will go to jail (also a state Notary who verified forged signature will go to jail as well)

most stolen cars go to spare parts or export to Global South as junk/scrap and you can't do that without DMV re-registration.

if you truly have modern car (like BMW 2017 or newer), then you can just disable and lock it remotely from an app, and geolocate it.

Almost no states I have bought and sold cars in requires a notary to do any regular title transfer.

Same in every state I've lived (7 at this point), all it requires is that the title is signed by the owner (or the signature looks like it was signed by the owner). The DMV /might/ care to look at the signature when they accepted it vs when they transferred it, or they might now. No notary or witness required.

In California I've heard that DMV can not, or will not, question a signature. I bought and sold cars to pay my way through college, during prime craiglist years, and had to 'recreate' countless signatures when forms were missing or required or even when I was lied to by sellers. Sounds reasonable I assume, unless we think there's a database of signatures somewhere in a government office DMV has access to, how in the world would they even be able to question a signature?

Every government issued ID I have ever had included my signature, so I assume they compare to that?

The same signature you scribbled on that unresponsive, old and abused touchscreen?

Are signatures even a good way to validate identity?

Probably not, I was just answering:

> how in the world would they even be able to question a signature?

When you buy a car, there is no requirement to provide the ID of the buyer. I suppose DMV could be detectives about it, and lookup old profiles of people on 20 year old titles and somehow match them to registered owners at that time to find their id profile, but no, this isn't done.

pls give me a state name, from my experience all state will require either in-person presence of an owner (verified by ID) or a notary who verified the signature of title holder for transfer

Idaho includes a tear-off bill of sale with the title. You just take that in to the court house and request a new title. You might even be able to do that through the mail.

https://www.autotrader.com/sell-car/in-ID

According to https://notary.pandadoc.com/knowledge-center/does-a-bill-of-... only Louisiana, Maryland, Nebraska, New Hampshire, Montana, and West Virginia require a notary on a bill of sale.

I’ve bought two used and one new car in NH and sold two used cars there; none of the bills of sale were notarized. I also brought 3 other used cars from out of state into NH, no notary there either.

California for starters with all 35 million residents. Nevada. Arizona. Oregon. Washington.

but the seller will have to be present and DMV verifies his ID.

You can't just steal a car with a title of somebody's name and transfer toy ourself, without the original owner and his ID present?

No the seller will not have to be present. No ID will have to be shown by anyone ever at any point.

Add Texas and New York to the list of states which don't require a notary for a private party vehicle transfer. Between NY, CA, and TX that's like 57M licensed drivers, so quite a few cars.

Speaking of bank safe boxes, when the IMF and the EU forced Greece into capital controls, meaning people could only get $400 a week out of their own accounts, plus money for rent...the safe boxes were also controlled. So you were no longer allowed to be alone with your safe box, an employee had to be present to make sure you're not getting money out of there.

https://www.reuters.com/article/eurozone-greece-cash/greeks-...

That type of room i not just a safe, but also a "panic room." Which could be anything from living in a terrible area and worried about civil unrest, to someone wanting a 100% confidence their tornado shelter would protect them no matter what.

In our case the panic room was definitely more weather related than burglary concerns. During the course of living in that location (I am in a different state now, but was there for 12 years in that house) we had 5 major weather incidents that were declared disasters by the state, and once nationally. We never had a single home invader, trespasser, burglar, or otherwise. The safe was more about fire risk than theft risk, but if you're going to do it you might as well go all the way. It was TL-30 rated but also rated for 4 hours at 2500F. Same thing with the safe room, if you're going to build it, might as well protect against everything.

Texas resident confirmed.

Not any more, but yep, I was a Texas resident when that work was done and that is where that house is located.

Off-topic, but could you tell me how much you think of your spending you recovered? Presumably lower home policy is a few hundred a year, and possibly you got a slightly higher price when you sold? I am ignoring your other soft benefits, and just curious about the financials.

I'd say over the course of the 8 years or so we had the setup, it saved us $1600 in homeowner's insurance premiums, and when we sold it helped us get maybe an extra $10k out of the sale price, so around $11600 recovered for around $55k spent total. By the numbers, it makes no sense to do this. Realistically by the numbers, it never makes sense to do anything to a house that is anything above the minimum legal requirements and what is currently trendy and en vogue with buyers. Another thing I did on that house that I liked but made no financial sense was to put in /very/ good windows all around (around $26k spent) which netted around $5k at sale.

All in, I spent around $90k in 12 years on the house, and the outcome was maybe $25k returned at sale. When you look at anything like that you should really consider how long you think you're going to stay there. I had intended to live in that house quite a lot longer, but life situations changed and I had to move out of state, so off to sale it went. Nonetheless, I don't regret any of the improvements I made because I got to live with those improvements and have a house that matched my needs/wants/desires. If I buy a house again (I'm currently renting), I'll probably have it custom built. There's simply no reason in my mind to put up with lowest-common-denominator mediocrity and normalcy in the highest cost thing you will likely ever purchase in your life, and the folks who do that to return a few higher percentage points of ROI at sale are treating themselves like they're a renter in a rental property, rather than treating themselves like a homeowner. A house isn't an investment, it's a place to live that you can do pretty much anything you want with it.

Non-eco concrete is also not fungible, there are many different kinds each with different mechanical properties.

TIL "RSC". TY.

> The only difference between me and every other random joe that buys a gun safe at bass pro/cabela's, is that I know what an /actual/ safe is, and I went about acquiring one rather than the cheap RSC you can bypass with a pry bar and a hammer or a sawzall.

While I'm on that topic, there's a few things everyone should know about safes.

An RSC, or Residential Security Container, has a very minimum standard, and the "gun safes" even though they are heavy and bulky at bass pro are usually RSCs. They are legally required to be marked, and if they are marked RSC, they are no more secure against burglary than your typical sheet-steel locking cabinet at the hardware store. Sometimes they're actually worse. The big thick door and the big thick walls on those "gun safes"? Well, generally it's two thin sheets of steel with drywall sandwiched between them. Why drywall? Well, it helps with fire protection and is the primary way in which the safe gets fire rated.

So let's talk about that drywall for a second. When you have a fire rated safe that uses drywall and it doesn't hermetically seal it, that drywall can actually cause corrosion of firearms or other metal objects and degradation of papers stored within the safe. Modern drywall is exceptionally corrosive, but usually this isn't a problem in homes because it's painted over on the inside to seal it and it off-gases to the outside where homes aren't perfectly sealed. In a safe though, you have a seam-welded outer shell, drywall, then carpet glued over it (which is also corrosive as well), or in better safes a seam-welded outer shell, drywall, then a tack welded inner shell with no carpeting.

Why does drywall cause corrosion and degradation of paper? Two compounds in drywall are responsible: Formaldehyde and Sulfur. Carpet also contains huge amounts of Formaldehyde typically, as does the carpet adhesive. Formaldehyde off-gasses and is itself deeply corrosive. Sulfur compounds in the drywall combine with moisture in the air to produce a chemical reaction when encountering naturally occurring pyrite in the powdered rock base of the drywall to produce iron hydroxide and sulfuric acid when coming into contact with exposed iron and high carbon steel (e.g. what guns are made of). The iron hydroxide off-gasses and the sulfuric acid is left behind and causes corrosion and pitting.

Don't be a big dummy, buy a real safe, not the crap they sell for thousands of dollars at big box stores with less than $100 in materials costs. If you are okay with the security level of an RSC you can get by with a plain locking steel cabinet.

I don’t think it’s an accident that a lot of the carbon sink concrete companies are doing precast products.

Factory conditions allow for tighter tolerances, which means you can dial in the product. Concrete poured outside has a range, and the worst case scenario is tightly controlled, but at the cost of potentially overspecced concrete. Or at least more expensive workers.

For some of those scenarios, couldn’t concrete be abandoned altogether?

Wooden building work pretty well, though forestry has plenty of its own problems (see New Zealand and it’s series of slash disasters).

China, by far the largest user here, builds very tall vacant buildings with concrete. Wood can only take you so high

With manufactured beams it can take you higher than you think, but building codes need to be adjusted.

Slash is an issue of bad practices. It's fixable with better management and isn't an inherient feature of forestry

Then you can just use a higher share of aggregate and/or partially substitute cement with weaker but more carbon-friendly pozzolans.

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