What if you made an entire city out of UHPC,How hard would it be to root out the defenders?
Difficulty would be above average.
>>64715359It would be very hard.
>>64715359It would be more difficult but with concrete it probably matters more how the buildings are designed than what grade they are.
>>64715359The difficulty would be Ultra High
>>64715591What was the point of building to that ugly-ass utility building in the middle of super expensive, high-rise neighborhood?
>>64715565You're a tall building.
>>64715609>"zombie" SHTF>lock them doors >...?>profit!
>>64715625>>64715625>>64715625>>64715625
>>64715609>he doesn't recognize itIt's one of the original NSA places of power anon, dating back to the 1970s.
>>64715359I tested it (with brass-covered, high-carbon 2800 Mpa steel microfibers, 2% volume). It resists the sledgehammer hits and makes a cool metallic sound when you hit it, but I don't think it can withstand multiple bomb hits in the same spot. It has a much lower fracture toughness than pure steel walls. My gut feeling is the only difference it makes is the attacker would need to spend ~10-20x more ammo to level the city. It's real use is in being water and gas impermeable, so the rebar inside never rusts, and you can make your thousand-year autismo fort. I'm the UHPC/RPC shill who posted in one of the "what material to make your /k house out of" a few years back.
>>64715799In the Russ-Uke war you can see sometimes russian drop 3ton of explosive on some Soviet commie block and it doesnt go down.
>>64715865It does, you just have to keep hitting.
>>64715865NTA but I dont think thermobaric bombs are good for destroying buildings, they're mostly dangerous for the people in the buildings? not sure about this tho
>>64715708it's a telephone exchange schizo
>>64715865Reinforced concrete is great at absorbing blast waves. That being said they do go down eventually.
>>64716073>Reinforced concreteThat's commie shitblox made from pre-fab panels that are welded together at 2 points with some grout slapped on seams. Many of the panels arent proper concrete either. only the load bearing ones/They were rated for 30 years and if the welds are not re-sealed they're card houses held together by the layer of new wallpapers and carpets.https://youtu.be/0vZMSSu1VDA?si=FJrc3Z5HuCShFWKj&t=248
>>64716072Bruhhttps://theintercept.com/2016/11/16/the-nsas-spy-hub-in-new-york-hidden-in-plain-sight/
>>64715649
>>64715609other than the NSA stuff that's the Telephone Switch.It handles all of the phone traffic for the 212 area code, which is the most important area code on earth.
>>64719311>other than the NSA stuff tPlease do not remind the citizens that they are being monitoredd 24/7.
>>64715359Uhpc is a fucking meme and youre gaySource:Am expert
>>64715799>t's real use is in being water and gas impermeable, so the rebar inside never rusts, and you can make your thousand-year autismo fort.What about microfibers rust near surface?
>>647200521) You manually push them under the surface when pouring. My best recipes made that solve for local sand and cement are fully water impermeable, I submerged samples underwater for 30 days and measured the added water weight, boiled them, stuffed them with metal rebar and fiber and left in the open for 2 years, etc. They have 8-20x less porosity than granite or slate, even 1.5-2 mm thick concrete coating protects the metal inside.But, also2) You don't need the fiberI'm not using any, only regular rebar. Fiber is more expensive, and I discovered UHPC not for blast resistance (fracture toughness), but for water and gas impermeability, to make a that will last forever. UHPC is still 4x the compressive and tensile strength of ordinary concrete, the high-carbon metal fibers are just a cherry on top science nerds added to give it more uses so it sells better.
>>64720138>to make a house*
>>64720138Are there any consumer bags of the stuff for us peons to mix and use yet?To protect exposed fibers, are you saying I just need to put on a layer of say...regular stucco over the UHPC structure, or put a layer of fiberless UHPC over the fibered one?Would slathering a layer over a cheaper cinderblock core reduce its longevity or would it last as long as a solid piece of UHPC so long as it was thoroughly covered and on a UHPC foundation?
>>64720138>>64720140Also by gas impermeable, does that include radon gas? So if one were to make a cellar or line their basement with UHPC, they could eliminate the buildup of radon gas?
>>64720138>the high-carbon metal fibers are just a cherry on top science nerds added to give it more uses so it sells better.So UHPC sauce is basically very very fine and clean silica fume and ground quartz powders added to the mix. And these powders block pores?
>>64720292I mean, you can probably just order it from your local ready mix plant. Most that aren't tiny little rural outfits will be able to do it.
>>64715609Google AT&T Long Lines. If you want to conceal huge square radio dishes this isn't that bad.
The only structure I know that can maintain its strength without using rebar is a dam body.
>>64720432
>>64720397Do I just roll up to my local Calportland in my S10 and just order UHPC dry mix?
>>64720292>Are there any consumer bags of the stuff for us peons to mix and use yet?I've seen them online, but the price is so high it invalidates the whole point of not having to rebuild every few generations. It's like 20x what normal concrete costs.For me it's ~2.6-2.8 times normal concrete in materials, but I also got lucky - one of my local quarries has very fine sand with the right proportion of 10-100 micron sized particles that replace the need for quartz powder (only silica fume and carboxylate plasticizer are needed beyond the usual ingredients) and gets me over the needed particle packing density.>>64720301>Also by gas impermeable, does that include radon gas?It should. I've read studies of multi-decade carbonization, the good recipes don't let carbon dioxide through, radon molecule is way larger than CO2.>>64720360>And these powders block pores?Not quite. When cement is mixed with water, the liquid is so alkaline it fuses calcium with most oxides, especially Sio2, Al2O3, MgO, etc, which is what sand, clay and granite/gravel are mostly made of. The resulting interfacial stone has many different molecule types collectively known as C-S-H groups. These are water insoluble up to a certain temperature (all you need to know is the threshold is above 100C), which is what makes concrete and mortar uniquely durable. Almost 100% of other construction materials very slowly degrade from water or UV (if it's a polymer).The fusing happens around nucleation sites. You need much finer SiO2 and Al2O3 containing materials like silica fume or metakaolin to create enough new nucleation sites that make sure the new C-S-H "stone" fuses fine and coarse aggregates without any holes ("capillary pores") in it. The quartz powder is only there because you need different grades of filler sizes to make the mix flow at lower water to cement ratio by displacing enough water.- bruh, post size limit
>>64720551-cont. Then you add polycarboxylate plasticizer and magic happens, you can achieve a workable mix at below (0.18 water (+ plasticizer liquid part)) / cement ratio and all capillary pores disappear: you have created UHPC.Don't ask me for the exact recipe, it won't work with your sand and the generic ones you can find online, just google any UHPC study. I've read ~1500 non-paywall studies online and spent 2 years making sample cubes, testing them in a lab (>60 tests) and by water immersing before I got 8-10 good recipes for my local cement and sand, yours will be different and you may need up to multiple micro quartz grades to compensate for really bad sand (also every cement manufacturer makes differently sized cement, it's not all 13-15 microns, and it that an enormous impact on surface area and thus packing density, shifting the proportion of ingredients you need).One advice I can give is if you buy premade, you should use kitchen scales to weight water and never, ever add more than what manufacturer tells you.
>>64720432The whole point of UHPC is your rebar will last forever. They literally submerged it in the ocean for years in a couple of studies I've read, the water doesn't get to rebar and it effectively lasts forever.UHPC-shill-anon
>>64720551>the price is so high it invalidates the whole point of not having to rebuild every few generations. It's like 20x what normal concrete costs.The value of well built homes and buildings might let you break even in about 20 years>only silica fume and carboxylate plasticizer are needed beyond the usual ingredientsCan you share your recipe or is it all proprietary still?
>>64720598>One advice I can give is if you buy premade, you should use kitchen scales to weight water and never, ever add more than what manufacturer tells you.Also: it's very easy to verify if you got the real deal: make a cube/rectangle that you can calculate the volume of, weight it on kitchen scales, submerge it in water for 30 days. Flip it while underwater a few times after 1-2 weeks to remove any gas pockets. After 30 days, pull it out, wipe it with a towel once on every side. It should weight no more than 1 gram above for a 10x10x10 centimeter cube, or about 1/2280th of it's original weight more. At worst, 2 grams.
>>64720598>Don't ask me for the exact recipe, it won't work with your sand and the generic ones you can find online, just google any UHPC studyAw shit i shoulda posted fasterI guess ill see what my local yard has and see what recipes I can match.
>>64720696How long for cure time b4 dunk test?
>>64720718UHPC (or really any concrete with a lot of silica fume, it's a curing accelerator) doesn't have the traditional 28-day hardening curve. More of the exponent happens by day 5, it's like 90% of max strength, but already solid and buildable on after 24 hours (at ~20C).My first wave of tests was done 2-3 days after pouring cubes, but I redid the tests on the same samples 180 days later and they all "improved", I even had some go from 6 grams to below 1 gram in a second 30-day test, sSo I don't have a real scientific answer. My gut feeling is the ones that were sub-2 grams when immersed on day 3 are still the best, even if many more become sub-2 half a year later. But if you dunk yours after 180 days and they are 1 gram, it would be good enough for me.
>>64720714It *really* depends on coarseness <> roundness, fineness (size) and fineness gradient (proportion of particles much, much smaller than the average) of every ingredient, the surface areas proportion is what matters and allows you to reduce empty space and displace enough water. If you just copy the 1000/250/1100/165/22 mix (and skip the quartz powder), when you try to mix with sub 0.18 w/c it will look "dry".
>>64719572>t. voted for the Peter Thiel aligned candidateI have nothing but scorn for you
>>64715799>It's real use is in being water and gas impermeable, so the rebar inside never rustsThe concrete makes the rebar rust, not external oxygen
>>64716073Have a WEBM.
>>64720138So what's the price difference with UHPC (or fibreless-UHPC)?Are there any downsides other than cost and maybe the weight of it?I built my place from ICF so it's already bulletproof and more durable than the typical home but it would've been cool to make it even tougher.
>>64715359>How hard would it be to root out the defenders?Seems easy, you guys really can't figure this out?
>>64715609illegal domestic spying operations hub
>>64720551>>64720598That is some quality postings in my internets
>>64721903>being so confidently wrongUntil alkalinity inside concrete drops below about 10.5ph, the steel rebar cannot rust even in the presence of chloride ions (which is how rebar in conventional concrete has a minimum design lifespan until the concrete carbonates or all of the Ca(OH)2 leaches off, despite CC not being a good insulator from water). Concrete and steel rebar are a match made in heaven.>>64722099With no fibers concrete has low fracture energy, much like bricks or glass - anywhere from 0.3 to about 0.9kJ/m2. UHPC with no fibers is around 1.2kJ/m2. Ordinary concrete with steel fibers can get up to about 5kJ/m2. UHPC with hooked 2-3% volume high-carbon steel microfibers (~10-15mm long, 0.3mm in diameter) can get up to about 45kJ/m2, google AI claims up to 70kJ/m2, but I haven't seen those studies. Still a far cry from pure steel, but at that threshold even jackhammering it apart becomes painfully slow. This effect is why it's used in some bunkers/skyscrapers.Besides fracture energy and increased tensile strength fiber doesn't add much else, costs a lot and is a pain to mix with (reduces mix workability). I don't use it & only care about UHPC for durability.(watch from 8:35)https://youtu.be/kDs_IMyB-YM?si=aamnjCN94upo9NnJ&t=515
>>64722099forgot: yes, cost is the main issue. Also it's very sticky when wet, washing equipment is a pain. Also, you cannot make it in a drum mixer, you need a hand mixer like you do for plastering mortar.It has no weight downside, weights a little less than ordinary concrete actually (~2280 kg/m3 vs ~2350 kg/m3)
>>64720450I doubt it. Why not just order a mixer with however much you need? What are you doing with it?
If rebars are placed too densely, the integrity of the concrete frame will be shredded by the rebars, but will this be ok if the balance is found to be just right, like the relationship between the hardness and toughness of the steel?
>>64722540What is your profession or do you do this autism for free? This sounds like it goes beyond the knowledge of a typical structural engineer. Also, with regards to material availability, are there areas where it is cheaper/easier to source the correct materials?
>>64720052>What about microfibers rust near surface?He's full of shit either way. Concrete protects the steel by creating an alkaline environment. That is lost at a rate of ~1mm per year.Once the first fibers aren't protected anymore they start to rust, same for the steel.And you WILL get water penetrating into the concrete sinc concrete and steel have different thermal expansion.If you really want to go for the 1000 year meme, build it like the fucking Pantheon, thick fucking walls with arches that are only ever compressed.
>>64723772>What is your profession or do you do this autism for free?I just wanted to build a house with my own hands that will last beyond a typical 100 year build, and the more I researched the topic, the more I realized no one knows anything and claims about materials you see are just marketing.I eventually settled on the need for a hard, non-porous, chemically inert material that does not permanently deform from seasonal temperature swings and started looking down the list of molecules/compounds at the end of reactions with high negative gibbs free energy. I basically ended up with oxides (glass, ceramics, brick), concrete, metal. Bricks and regular concrete are too porous and only last in climates with dry cold seasons (either low air moisture or it does not freeze regularly, which is how all the roman stuff survived mostly. Claims of roman concrete being anything exceptional in general are false, it's been tested in freeze-thaw camera and got equivalent to 15-17 freeze thaw cycle certification, if you google hard enough you'll find the article. The main reason it's any good is because of puzzolana, effectively a worse fly ash additive), and nonporous engineered ceramics are way, way too expensive to make a house out of. I looked into stainless steel, but it was still very expensive while not being fully chemically inert against standing salt water. Eventually I found UHPC, and it was perfect if I could make it on my own to save money.>are there areas where it is cheaper/easier to source the correct materials?Look for a lake quarry with very fine sand. It will cost like unwashed sand while not having excess clay particles and can remove the need for microquartz. There is nowhere else to save: you will have to pay for PCE superplasticizer and silica fume regardless, the only 1 to 1 alternative for silica fume is 18000m2/kg specific surface area metakaolin, and that is even more expensive than SF.
>>64724143>He's full of shit either way. Concrete protects the steel by creating an alkaline environment. That is lost at a rate of ~1mm per year.The mechanism by which concrete loses alkalinity ("carbonates") is CO2 ingress into it's capillary pores, UHPC doesn't have that.https://www.researchgate.net/publication/355094757_Corrosion_resistance_of_ultra-high_performance_fibre-_reinforced_concreteClick "download full text" and go to conclusions. There was also a 25 year scandinavian study that showed no carbonation progression in UHPC (it was called RPC before 2010), but I can't google it off the cuff.>And you WILL get water penetrating into the concrete sinc concrete and steel have different thermal expansion.You will not if the steel is fully inside concrete. It has been tested, you don't have to guess.>If you really want to go for the 1000 year meme, build it like the fucking Pantheon, thick fucking walls with arches that are only ever compressed.This will only work on very stable geology, arches create outward pressure that walls transfer onto your slab, but since you won't have one (not with rebar anyways), on the ground below the building. One hundred-year flood and your walls can slide apart, burying you under the arch.
>>64724522You mentioned the use of rebar rather than steel fibres as a cost saving and workability measure at the cost of toughness.Would there be a benefit to doubling up rebar with a reinforcing mesh? I'm thinking something like 19 gauge chicken wire. You'd have rebar for big loads and then the denser mesh to stop microcrack propagation in between.
>>64724615>Would there be a benefit to doubling up rebar with a reinforcing mesh?Yes. The drawbacks will also be the same: instead of less workability at the point of mixing it will be more difficult at the time of pouring. It took me like a month to figure out how to make the rebar holders from UHPC instead of plastic (otherwise there's a weak link leading to rebar), I have no idea how to hold a mesh in place tbqh.>like 19 gaugeBruh, lol (I'm in Europe), what are these units even.About microcracking: it has only happened to me in some recipes with too much cement (~>1180/m3), and never on the other ones, whether I added any fibers or rebar at all. I even built a UHPC house blind (is that what it's called in english?), a walkable, outwardly angled strip of concrete around the old house, and monitored it for a full year, no cracking anywhere, at all. It has only regular 12mm rebar.
>>64724666are you still forming expansion joints at typical spacing or are you able to get away with less? Have you tested expansion and contraction vs. more typical concrete? You gotta make a blog or something man otherwise this knowledge is lost.
>>64722540UHPC is useful for heavy loading like a skyscrapper foundations, a 155mm HE direct hit will easily put down a bunker with 10ft thick walls.It is cheaper and more effective use dirty to absorve the impact.
