🧵 Concrete
Anonymous at Sun, 16 Mar 2025 16:04:00 UTC No. 16620862
I've always been told that we use garbage concrete to make our sidewalks and streets because good quality stuff is to unfeasibly expensive, but what's stopping us from grabbing some Pozzolana from the nearest volcano putting it in the mixture and calling it a day?
Anonymous at Sun, 16 Mar 2025 16:35:59 UTC No. 16620924
>>16620862
because your mom tongues my anus
Anonymous at Sun, 16 Mar 2025 17:20:13 UTC No. 16620947
>>16620862
Pozzolana is unique to a single volcano in the world iirc. Not enough of it to cover the global demand of concrete.
Anonymous at Sun, 16 Mar 2025 17:33:27 UTC No. 16620959
>>16620947
well from what I read on the web, it said that Pozzolana is a term that covers all forms of pumice and volcanic ash, So i assumed you could just go to nearest volcanic source and scrounge up some volc ash to act as a nice reagent for concrete.
Anonymous at Sun, 16 Mar 2025 17:35:09 UTC No. 16620961
>>16620862
Depends on were you live but in here is common to use small rocks and river sand that's good quality
Anonymous at Sun, 16 Mar 2025 18:22:50 UTC No. 16621006
>>16620862
>>16620959
My local volcano was poached by illegals in league with Big Concrete.
Next closest volcano is on a whole other island.
Anonymous at Sun, 16 Mar 2025 18:24:38 UTC No. 16621007
>>16620961
>river sand that's good quality
What exactly am I looking for to know if my river sand is the good stuff?
Anonymous at Sun, 16 Mar 2025 18:41:46 UTC No. 16621021
>>16620862
Just invent hover cars and hoverboards (if it has wheels, it's not a hoverboard). Then roads and sidewalks can be nice grass paths.
Anonymous at Sun, 16 Mar 2025 18:53:08 UTC No. 16621035
>>16620862
Portland cement isnt garbage. Roman cement is garbage. Romaticized piece of shit
Anonymous at Sun, 16 Mar 2025 19:08:39 UTC No. 16621048
>>16621035
portland cement concrete = 50 years
roman cement concrete = 2000 years and counting (even in salt water)
Anonymous at Sun, 16 Mar 2025 19:41:55 UTC No. 16621076
>>16620862
>what's stopping us from grabbing some Pozzolana from the nearest volcano
How near is that?
Concrete is very cheap because it's made with very local materials.
Anonymous at Sun, 16 Mar 2025 19:44:35 UTC No. 16621079
>>16621035
>>16621048
Both CAN be excellent. Two caveats:
1. The Roman concrete which we observe today is just that which survived this long. Not the installations which failed.
2. Modern concrete structures almost always get iron rebar. This iron rebar WILL INEVITABLY corrode and this in turn will destroy the concrete structure. This process usually takes a few decades. You can count on pretty much any modern concrete structure to not last even two centuries BECAUSE OF THE REBAR.
Anonymous at Sun, 16 Mar 2025 19:50:08 UTC No. 16621085
>>16621079
why not plate the rebar in a non-corroding material.
Anonymous at Sun, 16 Mar 2025 19:55:43 UTC No. 16621093
>>16621085
That is sometimes done, but there are two problems with that.
1. It's MUCH more expensive (mostly because regular rebar is so cheap, literally anything else would be more expensive.)
2. If any of that coating becomes nicked or scratched, which is pretty much inevitable during the construction process, then corrosion will be focused down to that point and proceed even faster there.
Alternatives are to use something other than iron entirely, such as basalt fiber rebar which cannot corrode (but is WAY more expensive), or to use active galvanic protection, which again, is more expensive.
The reason most structures get built with regular rebar is because in most cases the people paying for construction think that the structure lasting 50-100 years will be good enough, and it's not worth spending more money on it.
Anonymous at Sun, 16 Mar 2025 19:59:20 UTC No. 16621098
>>16621093
It's also worth explaining the reason we use rebar at all; the Romans didn't after all. But Roman concrete without rebar could never be used for anything like this. Rebar gives enormous tensile strength to concrete. To build with concrete without the use of rebar is severely limiting and generally greatly increases the amount of concrete you'll have to use.
Anonymous at Sun, 16 Mar 2025 20:04:11 UTC No. 16621103
>>16621098
here's a cross section of the Pantheon in Rome, by far the most technically impressive feat of Roman concrete engineering which survives today (and perhaps ever). It used no rebar, so to make this work they needed to make it extremely thick (lost of material = lots of money) and it had to be a dome. They couldn't do concrete lintels with huge spans like we can today. They also used some other fancy tricks, like putting hollow pottery in the concrete near the top of the dome to reduce the weight of the dome.
Such a dome could be constructed with modern concrete, without the use of rebar, but nobody builds like this anymore because it's very expensive.
Anonymous at Sun, 16 Mar 2025 20:05:15 UTC No. 16621105
Anonymous at Mon, 17 Mar 2025 09:23:55 UTC No. 16621486
>>16620924
yummy, I hope you give mommy a sloppy kiss immediately afterwards
Anonymous at Mon, 17 Mar 2025 09:26:18 UTC No. 16621487
>>16621103
>>16621105
>ywn be a moderately rich roman noble at the height of the empire's power
It's simply not fair.
Anonymous at Mon, 17 Mar 2025 11:44:08 UTC No. 16621556
>>16620862
Shine light, of different frequencies, on that porous concrete rock. And you'll observe something similar to the photoelectric effect. Since metals have nano-pores.
Anonymous at Wed, 19 Mar 2025 05:47:25 UTC No. 16623376
reject concrete embrace brick
your fancy concrete buildings will be here for 20 years
in 2000 years brunel's bridges will be our coliseum
Anonymous at Fri, 21 Mar 2025 22:24:57 UTC No. 16625405
>>16621007
Pure sand (no organic matter) where the grains are angular and irregular. Desert sand is ground until too grains are round leaving poor adhesion that makes for poor concrete.
There is therefore a huge illegal market for good sand.
Anonymous at Fri, 21 Mar 2025 23:09:24 UTC No. 16625431
>>16625405
Thanks for the awesome answer dude.
Wrong sand, too much sand, too much wrong sand. Sounds like there's a lot of ways to go cheap.
Anonymous at Sat, 22 Mar 2025 00:32:45 UTC No. 16625474
>>16621048
>portland cement concrete = 50 years
Because of rebar
Portland concrete also has to take giant loads like 44 ton trucks running over it every minute and skyscrapers of 100 floors.
What did anyone do with roman cement? Some piece of shit stone road for a horse carriage once a day
Anonymous at Sat, 22 Mar 2025 00:42:31 UTC No. 16625479
>>16621103
>It used no rebar,
It uses iron braces on the external perimeter of the dome
Anonymous at Sat, 22 Mar 2025 02:42:10 UTC No. 16625540
Can use waste fly ash (loads of it laying around in dumps) instead of pozzolan, or biochar.
Anonymous at Sat, 22 Mar 2025 17:23:41 UTC No. 16625936
>>16620862
Why would I spend money to do that when I can just use the rocks and shit laying around next to my concrete plant?
Anonymous at Sat, 22 Mar 2025 17:38:19 UTC No. 16625956
>>16620862
Former concreter here, these days we use high and low MPa depending on the situation and budget.
We use 40 MPa for footpaths becuase they aren't under huge loads and they will be lifted by roots or ripped up for service works long before they break up.
For structures and water works we'll use 80 MPa to 120 MPa (in Australia, I have heard clap standards are shit).
And before someone asks yes Roman concrete was higher MPa, we could make it higher today but we would run into the issue they had, drying times measured in years.
Anonymous at Sun, 23 Mar 2025 17:11:02 UTC No. 16626748
>>16623376
I embrace stone with light applications of concrete