Concrete is pretty awesome substance to build bunkers and other fortifications. Cheap, versitile and usually easy to incorporate into any surrounding.
But the problem is that it's... not all that durable on the long term. if you look at bunkers of WW2 or so (or even younger ones) they quickly fall into disrepair. It just can't take the wear and tear of time. The climate and even mild acidity of rain will quickly crumble them.
Where as if you look at Ye Olde Schoole castles, they are pretty fine even after centuries of poor maintenance. They used STONE to craft those things, and while it was more difficult and expensive to work on, once it was build it was pretty much maintenance free for centuries.
So I was wondering if there was some modern technique to make "weather-proof" concrete, for structures that are meant to be there for not just 50 years but for 300 years later?
If we forget about the artillery, anc solely focus on "hwo to make things last for centuries" does concrete have any room in that discussion? Or are you more or less forced to rely on STONE?
Tell me the answer to the Riddle of Concrete!
Pictured: a bunker not 100 years old.
>>29536303
The Romans built concrete piers and docks that have survived over 1000 years submerged in salt water. The key was the volcanic ash used in the formula.
The modern evolution of this is geopolymer concrete, which should last pretty much forever. It actually incorporates water into the chemical structure instead of just being activated by it.
Another problem is the steel rebar. Once water infiltrates the concrete (at a rate of about 1 inch per year iirc) and hits the rebar, it begins to rust, swell, and spall. This kills the structure.
I love basalt rebar and basalt fibers. It is slightly more expensive than the steel rebar but has many advantages and will never rust or deform. Fireproof, better tensile strength, lasts forever. It is also the same density as concrete so the fibers mix easily and distribute evenly, and the rebar doesn't sink or float when you pour the mold, unlike steel or fiberglass.
Geopolymer concrete + basalt rebar = buildings and infrastructure that last effectively forever.
>>29536556
I had NEVER heard of BASALT rebar / basalt fibers. Or Geoplymer concrete.
Many thanks for these words I can use in my web-searches.
here, have some gun-porn.
>>29536556
Any idea how long the epoxy coatings they have started placing on rebar should last?
>>29536611
Chemically, nearly forever. But they're not terribly durable physically and if damaged while being installed the whole purpose can be defeated. On the other hand, modern structures aren't really made to last forever. Typically it's expected that they'll be torn down and replaced after about 50-70 years.
>>29536556
First I've heard of basalt reinforcement. Most of the time, if we've had corrosion issues, we used fiberglass or the epoxy coatings. I'll need to look into that.
Geopolymers are pretty cool, but there is a pretty serious catch, blast furnace slag and fly ash are becoming increasingly hard to come by with tightening environmental regulations. With as much political pressure out there as there is to kill coal fired power-plants, I'm expecting micro-silicates to become very rare/nonexistent within our lifetimes.
Then again, when they're done with coal, portland is probably next on the chopping block, so it may be a moot point.
>>29536556
In many ancient sieges, it was an effective tactic to undermine the walls-being-sieged and then light a heavy fire underneath them
(this was famously used in many sieges, including the siege of Rotchester where they used the fat from 40 biggest pigs they coudl find to fule the flames) in order to make the walls collapse.
So this miraculous basalt-rebar geopolymer concrete could easily take that kind of abuse?
The what about more direct hits from huge-as-fuck battering rams?
>>29536611
No idea. I'm not in the construction industry or an engineer or anything, so take all this info with a grain of salt.
I actually first heard about geopolymer and basalt rebar when I was researching how to build a Mars colony. Turns out this stuff is really interesting for uses here on Earth. There's been a few buildings built in Australia using geopolymer, seems to work fantastically.
The main obstacle preventing more widespread adoption is building codes and the lack of awareness about these materials. They are slightly more expensive than regular concrete construction and require different methods to use, but it's really not that difficult.
>>29536303
There is one thing about concrete is that when in civil applications sometimes you need to remove the structure.
Therefore sand is poured and mixed into the concrete. From what I know a higher ratio of sand mixed into the concrete will weaken the concrete's structural strength so it becomes more brittle.
>>29536755
The crazy thing is that this is the perfect use for fly ash. They have to pay people to take it away. I live in NC, and just recently we had a huge environmental problem when a bunch of that shit git into a river. Using fly ash in geopolymer would be the perfect use for this nasty stuff.
Iirc you need specific types of flyash though. Something to do with calcium content or something...
>>29536303
Keep in mind that many of these bunkers were designed to be placed in service as quickly as possible, with construction being sped up by using higher slump concrete, something that was accomplished by raising the water-cement ratio, which leads to higher porosity, higher elasticity, and generally weaker concrete.
The most common method to raise the slump available at the time was to use an ash (usually coal fly ash in the US), which gives the same ratio, but as water/(cement+pozzolan). Unfortunately, ash mixes generally have longer curing times. Other options are available, such as using particular aggregates and sands, but that is sort of grasping at straws.
Other issues were the curing controls or lack thereof. Temperature extremes during the initial set can cause premature failure or even destroy a structure. High humidity can affect finished surfaces, as can low humidity. Using concrete that is already into its Phase 1 hydration (approximately 2 hours, varies a lot with admixtures and temps) will make a crap structure. Incompletely mixing concrete will negatively affect hydration, leading to a shit structure.
A lot of concrete structures are shit because they were built like shit with a finicky, perishable material.
Also, basalt rebar is lighter, which is HUGE for forming times, especially above or below grade.
>>29536755
Here is a video about a guy using basalt on a small scale. https://youtu.be/mRWdHpopETI
>>29536888
Yeah using conscipts and POWs in construction is probably not the best thing for quality control.
>>29536864
You need pozzolan. Silicon or silicon and aluminum oxides that react with calcium hydroxide to produce cementatious material.
>>29536950
I can also imagine that those overseeing field construction probably cared more for checked (pill)boxes than for quality control of their subordinates work.
>>29536864
C-ash, sub-bituminous. Has a higher CaO content, which hydrates lime which then absorbs CO2 into calcium carbonate. F-ash requires an activator, sodium silicate is a common one I've read about.
Also, if NC has a abundance of the stuff, think you could send it over to GA? Some of our plants have complained about being able to get a hold of the stuff. Seems like plant Bowen is the only place to get it these days.
>>29536900
Thank you, I'll definitely be looking into this stuff
>>29536854
Sand and aggregates provide the bulk of most concrete. Straight Portland, or other cement, would be (wildly) too expensive and too difficult to work with due to the stresses of curing it.
Choice in aggregates and sands can greatly affect concrete, but their are methods in place to ensure that a quality product is batched. Bad concrete is always someone's fuck up.
While concrete can be made intentionally weaker, it is cheaper and easier to do this by raising the water-cement ratio.
>>29537087
Fly ash mixes can be batched with partial replacement without the use of explicit activator. Majority replacement may require an activator, depending on your cement. Our local plants are split between. Lafarge and GCN, results may vary, use as directed, no warranty expressed or implied.
>>29537292
I was speaking with regards to geopolymers, which make no use of portland, though looking back at it I realize than I segued into concrete plants with no preamble, so, oops?
Of course, all products undergo quality control testing and this does not constitute interest in or commitment to the acquisition of said products.
Lafarge is still around? I thought they got bought out.
This is a surprisingly knowledgable thread.
Between the burning of Rome, (thanks NERO), the destruction of the Library of Alexandria (ok, so my people screwed up a few times too...) and the constant sacking of Monasteries (basically, European Libraries and Banks in YE OLDE TYMES), we've lost a TON of technology. One of those things was how to make better masonry. Between those losses and being unable to decipher some Hieroglyphics from Egypt on THEIR masonry projects, we are stuck in the middle, hoping some lame-ass scientist can figure out the fomulaes. Having dealt with Concrete Formwork for a long time, yeah, it'd be nice to have the stuff from the old days.
Anyone have a clue how tough and durable 3d printed concrete buildings can be made?
Because it definitely has the potential to revolutionize the construction speed and cost of fortifications.
>>29537652
this is factually incorrect, yes a lot of knowledge was lost too what you have stated, what you are wrong on however is that we rediscovered all this information and technology and surpassed it long ago. what we have the capacity to complete now as far as masonry is concerned is far greater.
>>29537598
Yeah. I thought you were going to seque into batching.
As for Lafarge, they merged with Holcim, with some supply chains still bearing the Lafarge name. North Dakota is one of these.
QC is a fight here, though ready-mix concrete is like 97-98% of all yardage. The rest is flow fill. I get worried when the batchmen up here get ambitious and try "cutting edge" concrete technology. 5k mixes are hard for them and I only trust them to hit 4.5k every time.
>>29538366
Pre-cast is more likely to make a difference.
>>29538366
>Anyone have a clue how to fuck tradesmen into their graves yet again?
Ftfy
>>29538921
>buggy whip manufacturer angry about horseless carriages
>>29536755
>Typically it's expected that they'll be torn down and replaced after about 50-70 years.
Do you live in Rwanda or something?
>>29537599
Agreed.
I work at a lumberyard building center. It kinda freaks me out how much materials cost, knowing 2x4s are edible, flammable, weaken when wet for long periods of time, can rot etc.
This is the type of construction I am interested in.
>>29538842
>I get worried when the batchmen up here get ambitious and try "cutting edge" concrete technology.
My preferred way to waste downtime at work. Haven't really come up with anything good beside the realization that some chem cocktails do not perform as you might expect.
>>29537599
The more niche a subject is the more likely it brings out the pundits. It's also more likely to repel people who pretend they know stuff.
Thanks fellow Anons. I've learned something today.
>>29537652
While I'm sure that we did lose a lot of knowledge, you have to remember that Alexandria mainly held copies of written works. It's more than likely that the majority of information that burned existed elsewhere as well.
>>29536786
I'm pretty sure that sappers can figure out how to destroy anything, given time and sufficient explosives.
>>29536786
There isn't really anything that can be done against undermining aside from not letting your enemy do it. A structure is only as good as the ground it's sitting on.
>>29539457
Build the foundation into the bedrock.
>>29536602
Basalt is an amazing material, very underutilized IMO
>one of the most common resources on planet earth. Pretty much every country has some.
>completely non toxic, safe, and environmentally friendly (it's just rock)
>amazing properties for wide variety of uses.
The process for making this stuff is quite interesting too. Basically you melt the basalt rock and draw it out in very thin strands and then weave these into whatever you need.
As you can imagine this is a very energy intensive process and the equipment is rare. This is a big reason why most people aren't familiar with this material. Well that and the general conservative nature of the construction industry and fear of new things in regulatory bodies and zoning boards.
It's really cool stuff though. One more reason why we need more nuclear reactors. Cheap power = more possibilities.
>>29539263
Except they don't do it on their downtime. They throw 10cuyd of it in a truck and ask $1700 for it.
I get to deal with it 28 days later.
>>29536556
>>29536556
Fascinating, I hadn't heard of that before. It's odd to me modern concrete is missing that; I mean, I understand why, due to mass manufacture, but you would have figured we would have come up with a substitute sooner.
Still, that's a promising alternative. Eternal bunkers might be cool. Might make those old fallout shelters useful.
>>29539926
LAY THE FOUNDATION PUPPER
HAHHAHAHAHA SO FAHNY MEM
Fuck off.
>>29539849
Oh, yeah, that don't fly. When you're shipping to a buyer you give them exactly what they ask for. Experimenting is for the QC lab. Small scale before you take it big. Still, $170/yd isn't that bad(if you actually get what you want). Some of our mixes run $600
>>29539996
tbf, they were primarily using volcanic ash. The stuff isn't exactly ubiquitous. Or consistent. Throw in the fact that portland, maybe with some limited pozzolanic replacement has been doing the job for a while combined with >the general conservative nature of the construction industry and fear of new things in regulatory bodies and zoning boards.
It can be difficult for new tech to gain traction.
>>29536556
fiber reinforcement looks good on paper but the real world results turn out to be worse than just using rebar. rebar can survive a hell of a lot more in terms of impact and stress. also the fibers never fucking mix right.
>>29539534
can be easily cirncumvented, as other said, its a fruitless endeavor to argue if anything can be built to be resistance to active sapping.
>>29540220
$170 is the running ready mix rate with non-standard admixtures. It could be more, if you wanted a hydration controlled, water reduced concrete mix. Some low end suppliers are around $130 for large orders of 3000psi. These are all air entrained, which helps keep cost down a bit.
$600 a yard sounds about right for the guys up here who dabble with more advanced (usually pre-mix) stuff, which they usually use as "grout."
We get a lot of WR Meadows, Dayton Superior, and Western Material products. Short of the guys on site botching it, I never have issues with it.
If you dont care about the environment or health hazards, you can add asbestos fibers to concrete to make it stronger.
>>29541003
Why would you not care about health hazards? The point of a bunker is to keep you safe not give you cancer
/k/ - Experts on basalt-fiber geopolymer concrete engineering.
...never change.
Asbestos, it is the future gentlemen.
>>29536556
At first I thought basalt rebar was going to be some incredibly niche product, but you can just buy it online with a credit card. This is awesome.
>>29544077
>proven carcinogen
>future
>>29544116
I get the distinct feeling he was quoting some movie villain.
>>29544116
how is asbestos a "proven carcinogen"
???
>>29544142
http://lmgtfy.com/?q=asbestos+mesothelioma
>>29544116
Stop being a pussy
>>29544125
I wasn´t
>>29544149
I've never heard that before. How new is this?
>>29544162
The 1930s? But it didn't really become public until the 70s
>>29544108
A lot of those places will send you a sample pack to play with. Like a 1' piece of rebar, a few ounces of fibers, small spool of basalt rope. I saw some thin mesh made of basalt that looked really cool.
Crazy to think it's all made out of rock.
>>29536556
this is why i love /k/, even a thread about concrete turns interesting.
>>29545218
can't this stuff fuck up your lungs like asbestos?
>>29540294
One of the advantages of basalt fiber is that it mixes much better than fiberglass because it has the same specific gravity as concrete. Better tensile strength too.
>>29536303
>"weather-proof" concrete
Cladding.
>>29545249
Nah it's just rock dude. Completely non toxic. I mean I'm sure you could choke on it, and it might have some chemical coating on it or something, but basalt itself is perfectly safe.
>>29544142
Do you live in Asbest by any chance?
https://en.wikipedia.org/wiki/Asbest
>>29539926
lay the foundation pupper
>>29544142
Go home ivan
>>29545323
>Nah it's just rock dude.
You do realize where asbestos comes from don't you?
>>29537652
It's largely understood that Nero probably didn't burn Rome at all. In fact, some sources put him helping everyone as much as he could. It's likely that the story of him "playing his lute as Rome burned" was an attempt by his dissenters to downplay and discredit his popularity with the people after his death
>>29544066
But /k/s major is still bestiality.
>>29545323
Yes but one of the major reasons asbestos is dangerous is because of the fibers it is composed of. These break off in particulates small enough to be inhaled into the passageways in the lungs where they scar and cause issues with O2 absorption. These also have that risk just in a different probability because I do not have any OSHA standard for them off of the top of my head.
>>29536602
Im gonna just leave this here.
https://en.m.wikipedia.org/wiki/Biorock
>>29546058
Biorock was tested, turns out the rate of growth is 1/10 of what was claimed and electricity needed was 10x as much.
Cool idea but in practice it sucks.
