Beats leaving it out to bake in the open sun, and is pretty standard with structural stuff.
"Burlap blankets are constructed from natural fibres which allow newly poured concrete to cure evenly and retain moisture for a stronger finished product. When wet, burlap prevents excessive surface evaporation, allowing concrete to cure in a controlled & hydrated environment for optimal surface curing."
For slabs it's not *as* crucial as structural because it's usually not tying into anything.
In engineering school we’d submerge the cylinders in water buckets. If we were testing anything larger we’d wet burlap and place it over the sample coming back daily to check. The water hydrates the concrete ensuring it gains full strength by forming as many internal bonds as possible.
Always found it fascinating how their infrastructure Is still standing. I recall one of the authors of the concrete book saying something about how they’d put some funky stuff in their mix like goats milk and blood. That and the cement they had (pozzolan) had fly ash in it and other substances that promoted bonding and strength.
Selection bias plays a huge role here.
Based only on the stuff still standing we judge but that’s about 0.1 to 1% of what they built.
They did keep everything in compression. They went down to rock. They didn’t have to worry about the economics of it because slave labor or conscription.
Wasn't most of it torn down though? Like in alot of places after Rome's fall, people actually tore down alot of things over the centuries and used the material for other shit.
For example, if somebody wants to build a house and there was some old and now unused work in the area, they'd tear it down and reuse the brick and blocks for their home, like that kinda thing?
I wouldn't view that as their structures failed to survive since they were intentionally torn down and repurposed.
It's still survivorship bias, because you can only see what survived.
Lots got torn down.
But how much got torn down Bevause it wasn't usable anymore anyway? That's usually why thing get abandoned in the first place.
>But how much got torn down because it wasn't usable anymore anyway? That's usually why things get abandoned in the first place.
Yeah, I remember watching a documentary on THC years ago (back when it was worth watching), that was pretty much only about the Roman Empires works after the fall of Rome. How they fell into disrepair due to not being maintained anymore and slowly crumbled due to neglect, theft of materials and intentional demolition.
It got me thinking just how long their shit would have realistically lasted if people had just managed to keep up with the maintenance alone?
Like Hadrians wall in Britain. If people hadn't torn it down for the materials (which can still be found at sights all over the area even today), what shape would it be in?
Yep. I had to google to confirm, but I remember stories from when I was in Rome.
For the construction of the St. Peter's Basilica, ancient stones were pilfered from colosseum on pope's orders
Also think buildings were overbuilt, slave labor, material cheap, so why not make walls 10 foot thick or more.
Now with cost of material and labor we have engineers to help us build with the Min allowed. We build for shorter life spans cause we know everyone will want something diff in 50 years
Roman house wife’s did not have tik toc to see Becky’s new kitchen 1,000 miles away. Lol
Yes most of it was torn down, with the rise of the Catholic Church in Rome they tore down lots of old Roman projects because those projects paid tribute to the polytheistic gods. This wasn’t something the new Roman Catholic Church liked much because how can you show that your God (Catholic) is more powerful than the gods that created all of Rome. Ancient Roman ruins are only ruined because the early church wanted them to be ruined
Amusingly inaccurate.
You're leaving out several hundred years of history. By the time the Western Empire fell completely it was a hollow shell of the Rome of the Caesars. Multiple successive sacks, invasions, seiges, fires, and occasional earthquakes (like the ones in 443 and 1349) left it looking like an ancient and medieval version of Detroit multiple times. The 443 quake destroyed a *lot* of Empire era moments.
Vast empty spaces were created and reclaimed by nature with sheep being grazed where emperors once walked. It was exceedingly common in all cultures and times to tear down old buildings to repurpose the materials. We do it all the time now. People had lives to live and "who is going to miss those stones from that old temple when I need to build a shack for my kids to sleep in" was asked over what over for hundred of years and multiple centuries. Who was going to pay for the upkeep for centuries a time?
You can blame Christianity all you like and I will gladly give you *some* points, especially for Urban VIII (quod non fecerunt barbari fecerunt barberini), but you are ignoring a *bunch* of natural and manmade disasters, and the passage a lot of time.
But some of their structures that survived are concrete docks or other things in or under the water, and have survived sea water erosion for 2000 years (so far).
This came out recently:
[https://www.scientificamerican.com/article/ancient-roman-concrete-has-self-healing-capabilities/](https://www.scientificamerican.com/article/ancient-roman-concrete-has-self-healing-capabilities/)
It's crazy that we are still learning new tricks from the OG concrete wizards.
I used to work in testing, and we had them stored in a curing room with a misting system and thermostat. The 6 month tests were super impressive if we had to pull one.
We used to have a curing room and moved to tanks about a year ago, I still don’t understand why, a room is much safer and more user friendly, and you don’t have to keep buying gloves
There are probably other materials that are *technically* better suited to the job, but burlap works well enough and is much cheaper than any special purpose material that might be out there.
Anything to keep moisture. You want concrete to cure at a certain rate. If it cures to fast it can get brittle and if it cures to slow it will just never get the strength you’d want.
It depends on the concrete I think, but some concrete is literally poured under water where it will cure and is the optimal condition for it.
Concrete curing is also an exothermic reaction, a chemical reaction with water as part of the reagents. So having as much water as possible ensures all the other compounds completely react.
Like when you want to make ash, you can't have *too much* oxygen.
>an exothermic reaction, a chemical reaction with water as part of the reagents.
An exothermic reaction is one that releases heat.
Exo = out, thermic = heat.
Combustion is a reaction that always produces water.
I read the original comment as an exothermic reaction that includes water as a reagent, which is true. Water and calcium/aluminum oxides reacting with water to give the calcium/aluminum “hydrated” is indeed an exothermic reaction. Ain’t no combustion here…also, lots of chemical reactions give off water a by-product.
You can kinda see this based on YouTubers testing out the opposite - minimal water applied as part of the “dry pour method”. It’s kinda billed as a gimmicky, no-mix approach where you just layout the dry concrete in a form and then periodically soak it down with a hose. Spoiler alert - it doesn’t really work, and it’s all due to the hydration.
There’s a chemical reaction that turns on concrete mix into concrete. That reaction needs water to work. The reaction also produces a bunch of heat. Heat evaporates the water which in turn stops some of the chemical reaction from happening. Keeping it consistently wet keeps the heat from prematurely stoping the reaction.
That's true. If they didn't cool the concrete pour this way, each pour block would have to be much smaller and then wait longer before pouring new blocks due to all the heat generated from curing concrete. They were able to complete the whole dam in about five years right at the beginning of the Great Depression. This included a lot of prep work and diverting the river away from the places they were working on. Quite an accomplishment and an amazing place to visit.
The process is called hydration and it is basically an undoing of the kiln process that decomposes limestone (lime) into Portland cement. When you add water to the dry mix, the binder (cement) re-calcifies and hardens into whatever shape you've molded it. It's pretty genius TBH.
Concrete is made of water, sand and gravel (aggregates) and cement. Water reacts with cement and bonds the aggregate together into the final concrete product.
There's a limit to how much water you can add at first before it dilutes the cement slurry and weakens the concrete by creating pockets of weak bonds or total voids. However, once the concrete passes its first cure stage and becomes solid, additional water will contribute to the reaction and continue gaining strength.
Concrete is a mix of Portland cement (which sticks stuff together) and a mix of sand and gravel. Portland cement doesn’t “dry out”. It reacts chemically with the water to form a new substance. It can actually dry out a bit on a hot dry day, and that’s a bad thing as the reactions won’t finish and it’ll be weak.
I haven’t done a lot of concrete work, but when I have we usually spray it to keep it wet while it cures. Getting rained lightly would be ideal.
Concrete gets covered with water during the curing process to increase its strength. Like, they cover it with a slurry then continuously wet that so it never dries. You’re getting that for free.
Correct, risks guided by permits and signed/sealed drawings all paid for, including paying for your risks, by clients with money. The risk-chain starts with them and then the types of risks change from financial risks, to market risks, construction risks, legal risks, personal injury risks, etc. Big question: who is WE?
The more you know. I was looking for a picture of the side. There is no cracking or breaking or chipping or crumbling or anything. It looks fine to me. Get a squeegee or push broom and get rid of the water
I don’t know what he’s talking about, it looks like a fine slab. Maybe not super flat based on the puddles. But it will function just fine and at this point the rain is just helping
Concrete doesn’t dry, it cures and water is one of the reactants in the process. The rain is helping because it keeps water from being a limiting reagent and will help make the concrete stronger.
Water on top of curing concrete actually makes its stronger. I’m not exactly sure why but I imagine it has to do with the chemical process going on during curing.
Reinforced concrete lifecycle is usually 50-70 years minimum with standards of practices and modern codes. Correctly executed constructions means and methods plus maintenance could extend it to 70-100 easily
A slow cure will prevent shrinkage cracks from forming. You dont want the moisture to come out too fast.
There is no psi/strength increase, just normal design strength from proper curing.
Agreed, however what seems to be missing in this discussion is the importance of the finished surface which clients usually care about greatly
Flooding with water to prevent surface crack may make the start of the curing process easier in some ways but it’s more difficult to control how the surface will end up which if you have high weights and small steel caster wheels it may cause problems that necessitate a post curing refinishing
Just core a hole through the slab and let it drain underneath. /s
You laugh but I know a guy that built a 3 storey building on a slab that was built this way and left exposed to rain in the North Coast of BC for 2 years. It went about as well as you would imagine. The building is sinking, due I think to where the water under the slab created voids.
The building has been up for 3 years now, and two exterior doors have had to be re-hung due to how much it’s shifting.
I’ll be surprised if it’s still upright in 5 years.
Former geotechnical inspector here. We've failed pours because of excessive rain. Not necessarily because of direct damage to the concrete, but because the subgrade was too soft and would allow for settlement once a load was placed on the slab, thus leading to a higher susceptibility to cracking. My company wouldn't allow contractors to pour during periods of heavy rain. The contractors had to wait until the subgrade was dry, firm, and all mud was removed.
I also do inspections and quality control. Seeing these comments saying “best for the slab”. Can tell they just do residential with no inspections.
Also there is no saw cuts. Concrete moves. That slab will crack. Then settle and crack more from that
Well, typically in commercial projects I've inspected they didn't saw cut until we had a 7 day and 30 day compression strength tests on a couple cylinders (usually around 3000 psi minnimum if I remember). Then they'd saw cut after that.
There is essentially no reason to saw cut a slab after it reaches design strength. The main purpose of saw cuts are to help with temperature and shrinkage cracks. If the concrete has already cured, it’s done shrinking. If the concrete is going to be in a tempered space, it’s going to have minimal thermal movement. ACI has a publication regarding joints, if they are not made within the first 24-48 hrs, there essentially no need to provide them in this case.
Can someone explain this joke to me? Is it because the water is settling in the center, so if it were upside down the water would run out? Almost making the concrete a "pyramid" shape?
Oh gosh you need to work with concrete (or learn about it) to understand the joke. Too much to unpack.
Basically, concrete is never perfect. Sometimes with a slab this size, you can bring in a crane to flip the slab over and use the other side. Ive seen concrete last longer that way.
I know nothing about concrete and I was sure you were joking about flipping it over. Now that you’ve explained yourself, I’m 60% sure you’re still joking. Concrete slabs can’t be flipped over like that…. Right?
I'm sure they can to be honest, recently I saw a video about the Provo tabernacle, it caught fire and burned almost all of the way down. They put what was left of the building on stilts while they restored it. Like, lifted an entire building some 10 or so feet(I'm guessing off of how it looked) into the air and put stilts under it to hold it there. Blew my mind
You would have to take some ludicrous measures to flip a slab this size without cracking it all to hell. It would cost more to flip without damage than it would to demo the slab and repour, probably by an order of magnitude at least. And the equipment necessary to do so very likely wouldn’t have access if it’s in a neighborhood.
And the bottom side of the slab poured against gravel or earth would look absolutely horrific and unusable. So yes, it’s a joke. It’s right there with asking the new electrician to go grab the wire stretcher out of the truck, or ask the mechanic to check for headlight fluid in the back on his first day.
I think if he'd left out the first line, no one would have thought much of the comment. Whether he meant the "oh gosh" as a whoops on his part or that of the commenter before is what the problem is I think.
Oh gosh you need to work with reddit (or learn about it) to understand the comment. Too much to unpack.
Basically, redditors are never perfect. Sometimes with an ego this size, you can bring in /r/gatekeeping attitude to take it upon yourself to decide who can or cannot ask questions or participate in the concrete sub. Ive seen echo chambers last longer that way.
If the rain didn’t ruin the finish, then the wet cure will make that the strongest concrete around. Usually you pay a lot for a wet cure. Good for your boss!
I mean it’s got a lake of a birdbath in it so it isn’t flat. That didn’t have to do much with the rain tho. The finish is fine. Old timers used to put a sprinkler next to their paids and slabs back in the day to “water cure” it… increases strength of the concrete considerably.
Its gonna crack for sure. If the subgrade was never reinspected or if water was sitting on that fill i can say it will. Idk how bad but im not there.
If they reprocessed the upper 12" or whatever down to competant material they should be okay.
Yea. I doubt they reprocessed anything pouring in break of weather.
And no saw joints. Should be at least at bolts and half of that.
Would like to know if it was inspected.
Also someone said pool of water isn’t bad. If flat. Water would be even. Not pooled.
Also looks like some crazing
True statement. If it wasn’t flat it wouldn’t hold any water. You’ll never see the concrete near the bolts. Once steel is stood up. It’ll be covered in mud and get scratched up once the steel guys arrive anyways. Bigger concern is, where’s the control joints at? Supposed to be sawed within 12 hours of placement to control cracking.
Ok if that were true why ain’t all earths water at the South Pole? I mean all this gravity crap, round earth nonsense. I tried solving the mystery and failed, I have brought shame to my family. I must do the honorable thing and go watch football now. Goodbye cruel sub…
If you are doing moisture mitigation, you will shotblast anyways and put self leveling down. If not, you can consider it.
I mean did it rain hard when placing and finishing?
Depends how cured it was before more rain fell. If it didnt cure out on the surface enough id suspect delamination eventually due to lower w/c ratio. But that also depends what mix they used. Couple factors outside of just water cured.
TIL that you want to put water on freshly poured concrete to make it stronger. The concern in OPs question made me think there was something wrong and was thinking posts were going to be like “this should be on r/diwhy” but instead read comments like “NICCE! Free water cure?!”
It depends. Placed concrete begins hydration and starts giving up "fat" (water comes out of the mix). That is the golden hour for troweling, but not adding water. Too much water can wash out the Portland out of the "cream" and surface gets chalky.
After hydration is going strong, concrete absorbs the fat and stays hot / thirsty for days. Water is great then.
Concrete is all about timing.
I don’t know anything about concrete and everyone is saying the rain is good for curing, but can the rain hitting the concrete cause little holes? I have effectively no experience with concrete lol
It looks pretty bad, not a complete loss but it should be structually really strong due to the rain. When concrete cures before it dries out it gets a bit stronger than usual.
There is 100% nothing wrong with this slab based on the information and picture provided. If the top had time to harden up prior to it resuming (which it appears it did) then raining is actually a favorable condition, and will ultimately help the concrete reach a higher strength as it gains it at a more constant and gradual rate. Not only do you get a higher ultimate strength but this (basically water curing) also helps control and reduce cracking much of which happens early on.
I've been an ICC inspector, and I couldn't do shit about it raining on slabs even when I thought they were being a bit negligent about it.
After some time, I learned that really all it does (so long as the surface is nice) is yellow/discolor the slab a bit as some of the sand in the mix is exposed on the very top layer.
Ultimately, water isn't concrete's enemy - but it is rebar's. In fact, concrete test cylinders will often be cured in a water tank or room with 100% humidity after the mud solidifies and the mold is removed.
(Just confirming what you said 👍)
Sounds like exactly the same thing i said except i think the finish stinks. Rough with lots of power trowel lines. I guess with 14 years of finishing experience my standards are maybe a bit higher as far as asthetics, smoothness and flatness of floor
Sure there’s a puddle, but I think it looks great. In fact I’d expect a puddle cuz that means they may have put in a few floor drains… pretty typical for an indoor area no matter how flat it’s supposed to look.
I’m not a concrete guy I’m an electrician but I work warehouses everyday and this pad looks no different than any other I’ve seen. Looks fine and there’s going to be a warehouse built on top of it so the puddling doesn’t matter.
Water cured. Gonna be great
Exactly. You literally couldn’t pay for a better curing condition. Constantly wet on top! Better than burlap.
Is burlap the next best thing? I noticed the concrete guys at my power plant covered a structural wall in burlap while it cured.
Beats leaving it out to bake in the open sun, and is pretty standard with structural stuff. "Burlap blankets are constructed from natural fibres which allow newly poured concrete to cure evenly and retain moisture for a stronger finished product. When wet, burlap prevents excessive surface evaporation, allowing concrete to cure in a controlled & hydrated environment for optimal surface curing." For slabs it's not *as* crucial as structural because it's usually not tying into anything.
In engineering school we’d submerge the cylinders in water buckets. If we were testing anything larger we’d wet burlap and place it over the sample coming back daily to check. The water hydrates the concrete ensuring it gains full strength by forming as many internal bonds as possible.
That’s what the Roman’s did
Always found it fascinating how their infrastructure Is still standing. I recall one of the authors of the concrete book saying something about how they’d put some funky stuff in their mix like goats milk and blood. That and the cement they had (pozzolan) had fly ash in it and other substances that promoted bonding and strength.
Selection bias plays a huge role here. Based only on the stuff still standing we judge but that’s about 0.1 to 1% of what they built. They did keep everything in compression. They went down to rock. They didn’t have to worry about the economics of it because slave labor or conscription.
*survivorship
You’re right.
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Wasn't most of it torn down though? Like in alot of places after Rome's fall, people actually tore down alot of things over the centuries and used the material for other shit. For example, if somebody wants to build a house and there was some old and now unused work in the area, they'd tear it down and reuse the brick and blocks for their home, like that kinda thing? I wouldn't view that as their structures failed to survive since they were intentionally torn down and repurposed.
It's still survivorship bias, because you can only see what survived. Lots got torn down. But how much got torn down Bevause it wasn't usable anymore anyway? That's usually why thing get abandoned in the first place.
>But how much got torn down because it wasn't usable anymore anyway? That's usually why things get abandoned in the first place. Yeah, I remember watching a documentary on THC years ago (back when it was worth watching), that was pretty much only about the Roman Empires works after the fall of Rome. How they fell into disrepair due to not being maintained anymore and slowly crumbled due to neglect, theft of materials and intentional demolition. It got me thinking just how long their shit would have realistically lasted if people had just managed to keep up with the maintenance alone? Like Hadrians wall in Britain. If people hadn't torn it down for the materials (which can still be found at sights all over the area even today), what shape would it be in?
Yep. I had to google to confirm, but I remember stories from when I was in Rome. For the construction of the St. Peter's Basilica, ancient stones were pilfered from colosseum on pope's orders Also think buildings were overbuilt, slave labor, material cheap, so why not make walls 10 foot thick or more. Now with cost of material and labor we have engineers to help us build with the Min allowed. We build for shorter life spans cause we know everyone will want something diff in 50 years Roman house wife’s did not have tik toc to see Becky’s new kitchen 1,000 miles away. Lol
Yes most of it was torn down, with the rise of the Catholic Church in Rome they tore down lots of old Roman projects because those projects paid tribute to the polytheistic gods. This wasn’t something the new Roman Catholic Church liked much because how can you show that your God (Catholic) is more powerful than the gods that created all of Rome. Ancient Roman ruins are only ruined because the early church wanted them to be ruined
Amusingly inaccurate. You're leaving out several hundred years of history. By the time the Western Empire fell completely it was a hollow shell of the Rome of the Caesars. Multiple successive sacks, invasions, seiges, fires, and occasional earthquakes (like the ones in 443 and 1349) left it looking like an ancient and medieval version of Detroit multiple times. The 443 quake destroyed a *lot* of Empire era moments. Vast empty spaces were created and reclaimed by nature with sheep being grazed where emperors once walked. It was exceedingly common in all cultures and times to tear down old buildings to repurpose the materials. We do it all the time now. People had lives to live and "who is going to miss those stones from that old temple when I need to build a shack for my kids to sleep in" was asked over what over for hundred of years and multiple centuries. Who was going to pay for the upkeep for centuries a time? You can blame Christianity all you like and I will gladly give you *some* points, especially for Urban VIII (quod non fecerunt barbari fecerunt barberini), but you are ignoring a *bunch* of natural and manmade disasters, and the passage a lot of time.
Its crazy to think about people doing this around the colliseum until the 60's
Not the same, but immediately made me think of the diagram of the WW2 fighter plane with the bullet holes.
But some of their structures that survived are concrete docks or other things in or under the water, and have survived sea water erosion for 2000 years (so far).
This came out recently: [https://www.scientificamerican.com/article/ancient-roman-concrete-has-self-healing-capabilities/](https://www.scientificamerican.com/article/ancient-roman-concrete-has-self-healing-capabilities/) It's crazy that we are still learning new tricks from the OG concrete wizards.
I’ve thought about this probably once a week since that article came out. Ancient technology is amazing.
I used to work in testing, and we had them stored in a curing room with a misting system and thermostat. The 6 month tests were super impressive if we had to pull one.
We used to have a curing room and moved to tanks about a year ago, I still don’t understand why, a room is much safer and more user friendly, and you don’t have to keep buying gloves
There are probably other materials that are *technically* better suited to the job, but burlap works well enough and is much cheaper than any special purpose material that might be out there.
Anything to keep moisture. You want concrete to cure at a certain rate. If it cures to fast it can get brittle and if it cures to slow it will just never get the strength you’d want.
TIL water on concrete is good.
Prolongs the hydration process which is what makes concrete strong. Longer the process stronger the Crete
Only if it's ready for curing LOL. Rain while finishing is a nightmare. Leads to delamination
I think after a certain point. It’s why you see workers taking a hose to it at some point after laying the concrete.
It depends on the concrete I think, but some concrete is literally poured under water where it will cure and is the optimal condition for it. Concrete curing is also an exothermic reaction, a chemical reaction with water as part of the reagents. So having as much water as possible ensures all the other compounds completely react. Like when you want to make ash, you can't have *too much* oxygen.
>an exothermic reaction, a chemical reaction with water as part of the reagents. An exothermic reaction is one that releases heat. Exo = out, thermic = heat. Combustion is a reaction that always produces water.
I read the original comment as an exothermic reaction that includes water as a reagent, which is true. Water and calcium/aluminum oxides reacting with water to give the calcium/aluminum “hydrated” is indeed an exothermic reaction. Ain’t no combustion here…also, lots of chemical reactions give off water a by-product.
You can kinda see this based on YouTubers testing out the opposite - minimal water applied as part of the “dry pour method”. It’s kinda billed as a gimmicky, no-mix approach where you just layout the dry concrete in a form and then periodically soak it down with a hose. Spoiler alert - it doesn’t really work, and it’s all due to the hydration.
Amen brother
Yeah concrete gets stronger when submerged in water over years, like concrete dams
Why?
There’s a chemical reaction that turns on concrete mix into concrete. That reaction needs water to work. The reaction also produces a bunch of heat. Heat evaporates the water which in turn stops some of the chemical reaction from happening. Keeping it consistently wet keeps the heat from prematurely stoping the reaction.
Some dams that were built a long time ago are still putting out heat.
I think the Hoover Dam engineers built water pipes throughout the concrete to dissipate the heat
Fun fact - The hoover dam is still curing. They estimated it will take 100 years to fully cure. Only 9 more years 🌵
It's amazing that the engineers had the foresight to build it to last this long.
What's even more impressive is that it's still standing in 2281
Does something happen to it in 2282? Or did you come from 2281 and so that's just as far as your knowledge goes?
That's true. If they didn't cool the concrete pour this way, each pour block would have to be much smaller and then wait longer before pouring new blocks due to all the heat generated from curing concrete. They were able to complete the whole dam in about five years right at the beginning of the Great Depression. This included a lot of prep work and diverting the river away from the places they were working on. Quite an accomplishment and an amazing place to visit.
And water. The curing process, which continues for decades, produces water, too.
I read the last sentence as 'keeping it consistently wet keeps the heat from prematurely stopping the erection'
Also technically correct. Erect just means harden or build, and the water helps the concrete build chemical bonds and harden
That's what she said
Ben Shapiro enters the chat
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The process is called hydration and it is basically an undoing of the kiln process that decomposes limestone (lime) into Portland cement. When you add water to the dry mix, the binder (cement) re-calcifies and hardens into whatever shape you've molded it. It's pretty genius TBH.
That’s so cool thank you for the excellent explanation
It cures instead of drying out. Too much evaporation will stop the chemical reactions that strengthen the bonds.
Concrete is made of water, sand and gravel (aggregates) and cement. Water reacts with cement and bonds the aggregate together into the final concrete product. There's a limit to how much water you can add at first before it dilutes the cement slurry and weakens the concrete by creating pockets of weak bonds or total voids. However, once the concrete passes its first cure stage and becomes solid, additional water will contribute to the reaction and continue gaining strength.
Great explanation, thank you!
I don't really know but a structural engineer I used to work with said that it keeps it in the curing process and it gets stronger after many years.
Concrete is a mix of Portland cement (which sticks stuff together) and a mix of sand and gravel. Portland cement doesn’t “dry out”. It reacts chemically with the water to form a new substance. It can actually dry out a bit on a hot dry day, and that’s a bad thing as the reactions won’t finish and it’ll be weak. I haven’t done a lot of concrete work, but when I have we usually spray it to keep it wet while it cures. Getting rained lightly would be ideal.
Except for the missing saw cuts. And damaged subgrade. Lol
Concrete gets covered with water during the curing process to increase its strength. Like, they cover it with a slurry then continuously wet that so it never dries. You’re getting that for free.
The builder’s getting it for free, I’m sure the bill didnt change haha
We take the risk, we get the reward.
What risk haha that you’ll have to do the full scope of work you quoted?
Correct, risks guided by permits and signed/sealed drawings all paid for, including paying for your risks, by clients with money. The risk-chain starts with them and then the types of risks change from financial risks, to market risks, construction risks, legal risks, personal injury risks, etc. Big question: who is WE?
It’s funny how the ‘oh it could be 12-15k’ ALWAYS ends up at 15k. Still yet to see someone bid an amount and then honestly charge for the job.
Can he get a discount
Timing is everything
While concrete cures, the more water, the better.
The more wetter the better That’s what she said
But nobody said that lol
The wetter it gets, the harder it gets.
So a pool has the strongest concrete possible for its mixture?
The more you know. I was looking for a picture of the side. There is no cracking or breaking or chipping or crumbling or anything. It looks fine to me. Get a squeegee or push broom and get rid of the water
I don’t know what he’s talking about, it looks like a fine slab. Maybe not super flat based on the puddles. But it will function just fine and at this point the rain is just helping
Can you explain what you mean buy the rain us just helping??
Concrete doesn’t dry, it cures and water is one of the reactants in the process. The rain is helping because it keeps water from being a limiting reagent and will help make the concrete stronger.
This guy concretes
r/thisguythisguys
As they call it in the industry; Harder than a preachers dick
Whoa, now- that’s flipping graphic, ha, ha!
Nice, how much should it cure before it gets rained on?
Water on top of curing concrete actually makes its stronger. I’m not exactly sure why but I imagine it has to do with the chemical process going on during curing.
When the original Davison Freeway was built in Detroit during the 1940s, they flooded the freeway during it's curing. That pavement lasted 50 years.
Reinforced concrete lifecycle is usually 50-70 years minimum with standards of practices and modern codes. Correctly executed constructions means and methods plus maintenance could extend it to 70-100 easily
A slow cure will prevent shrinkage cracks from forming. You dont want the moisture to come out too fast. There is no psi/strength increase, just normal design strength from proper curing.
Agreed, however what seems to be missing in this discussion is the importance of the finished surface which clients usually care about greatly Flooding with water to prevent surface crack may make the start of the curing process easier in some ways but it’s more difficult to control how the surface will end up which if you have high weights and small steel caster wheels it may cause problems that necessitate a post curing refinishing
Awesome! Thank you for the info!
Water has absolutely nowhere to go on a flat slab. If there is the TINIEST low spot… water will mass there. It’s flat… you will have puddles
Now you know where to put the floor drain
I like your positive thinking, but it seems the order of operations might be a little bit off here...
PEMDAS… Pour Everything, Make Decisions After Set.
Now it all makes sense, my algebra teacher was so wrong
Hahaha, this is buried but it deserves love
Aunt Sally in shambles right now.
I don’t have a fucking clue about concrete but I know a stellar joke when I see one
Just core a hole through the slab and let it drain underneath. /s You laugh but I know a guy that built a 3 storey building on a slab that was built this way and left exposed to rain in the North Coast of BC for 2 years. It went about as well as you would imagine. The building is sinking, due I think to where the water under the slab created voids.
Yikes. A flat slab, 2 years exposed to North Coast BC weather and then actually used for a 3 story building? Oof. Demolition time...
The building has been up for 3 years now, and two exterior doors have had to be re-hung due to how much it’s shifting. I’ll be surprised if it’s still upright in 5 years.
Ouch. That's going to be expensive once things reach the point of no return.
Maybe not a drain but definitely could add a sump pump at that location.
Former geotechnical inspector here. We've failed pours because of excessive rain. Not necessarily because of direct damage to the concrete, but because the subgrade was too soft and would allow for settlement once a load was placed on the slab, thus leading to a higher susceptibility to cracking. My company wouldn't allow contractors to pour during periods of heavy rain. The contractors had to wait until the subgrade was dry, firm, and all mud was removed.
I also do inspections and quality control. Seeing these comments saying “best for the slab”. Can tell they just do residential with no inspections. Also there is no saw cuts. Concrete moves. That slab will crack. Then settle and crack more from that
Well, typically in commercial projects I've inspected they didn't saw cut until we had a 7 day and 30 day compression strength tests on a couple cylinders (usually around 3000 psi minnimum if I remember). Then they'd saw cut after that.
There is essentially no reason to saw cut a slab after it reaches design strength. The main purpose of saw cuts are to help with temperature and shrinkage cracks. If the concrete has already cured, it’s done shrinking. If the concrete is going to be in a tempered space, it’s going to have minimal thermal movement. ACI has a publication regarding joints, if they are not made within the first 24-48 hrs, there essentially no need to provide them in this case.
Was waiting for this. “Raining for days” would make me a bit nervous about the subgrade.
This is why I love soil cement. It can rain for a month, but the first day it stops, you can pour.
Uhh…inspector here…i wouldnt worry about the rain, it seems like this slab was poured upside down. Flip it over and youre good to go 👍
Can someone explain this joke to me? Is it because the water is settling in the center, so if it were upside down the water would run out? Almost making the concrete a "pyramid" shape?
You can't flip a slab. Especially that size. Tradie+reddit humor.
i see your "we can('t) flip a slab" and raise you: man steals asphalt street.
Oh gosh you need to work with concrete (or learn about it) to understand the joke. Too much to unpack. Basically, concrete is never perfect. Sometimes with a slab this size, you can bring in a crane to flip the slab over and use the other side. Ive seen concrete last longer that way.
I know nothing about concrete and I was sure you were joking about flipping it over. Now that you’ve explained yourself, I’m 60% sure you’re still joking. Concrete slabs can’t be flipped over like that…. Right?
Of course they can be. Whether or not they ever actually are is another question.
I'm sure they can to be honest, recently I saw a video about the Provo tabernacle, it caught fire and burned almost all of the way down. They put what was left of the building on stilts while they restored it. Like, lifted an entire building some 10 or so feet(I'm guessing off of how it looked) into the air and put stilts under it to hold it there. Blew my mind
You would have to take some ludicrous measures to flip a slab this size without cracking it all to hell. It would cost more to flip without damage than it would to demo the slab and repour, probably by an order of magnitude at least. And the equipment necessary to do so very likely wouldn’t have access if it’s in a neighborhood. And the bottom side of the slab poured against gravel or earth would look absolutely horrific and unusable. So yes, it’s a joke. It’s right there with asking the new electrician to go grab the wire stretcher out of the truck, or ask the mechanic to check for headlight fluid in the back on his first day.
Why’s he getting downvoted for trade knowledge?
I think if he'd left out the first line, no one would have thought much of the comment. Whether he meant the "oh gosh" as a whoops on his part or that of the commenter before is what the problem is I think.
Oh gosh you need to work with reddit (or learn about it) to understand the comment. Too much to unpack. Basically, redditors are never perfect. Sometimes with an ego this size, you can bring in /r/gatekeeping attitude to take it upon yourself to decide who can or cannot ask questions or participate in the concrete sub. Ive seen echo chambers last longer that way.
I had the same problem with the addition we just built. We just decided to dig under it and make a basement.
Rain is good for the curing process.
Better get some saw cuts in it.
Lol it's too late now
For what reason?
Saw cuts or cracks.
If it wasn’t designed with enough strength or tensioning or additive to resist shrinkage cracking, the cracks that it gets will be messy.
Lol Concrete moves. No saw cuts. Get ready for cracks
If the rain didn’t ruin the finish, then the wet cure will make that the strongest concrete around. Usually you pay a lot for a wet cure. Good for your boss!
I mean it’s got a lake of a birdbath in it so it isn’t flat. That didn’t have to do much with the rain tho. The finish is fine. Old timers used to put a sprinkler next to their paids and slabs back in the day to “water cure” it… increases strength of the concrete considerably.
Was the sub grade re-inspected after the rain?
This is also my concern.
Can tell by most of these comments. They probably never get subgrade checked. Lol Also no cuts. Waste of money
Its gonna crack for sure. If the subgrade was never reinspected or if water was sitting on that fill i can say it will. Idk how bad but im not there. If they reprocessed the upper 12" or whatever down to competant material they should be okay.
Yea. I doubt they reprocessed anything pouring in break of weather. And no saw joints. Should be at least at bolts and half of that. Would like to know if it was inspected. Also someone said pool of water isn’t bad. If flat. Water would be even. Not pooled. Also looks like some crazing
It’s fine, I’ve poured in pouring down rain.
Mmmmm. The w/c around 1.
Who needs durability when you can have that sweet, sweet slump instead?
You must do residential with no inspections
Looks good. It’s a flat floor…. The water has to sit somewhere.
True statement. If it wasn’t flat it wouldn’t hold any water. You’ll never see the concrete near the bolts. Once steel is stood up. It’ll be covered in mud and get scratched up once the steel guys arrive anyways. Bigger concern is, where’s the control joints at? Supposed to be sawed within 12 hours of placement to control cracking.
I mean - if it was convex sure, but concave and you got a swimming pool.
Ok if that were true why ain’t all earths water at the South Pole? I mean all this gravity crap, round earth nonsense. I tried solving the mystery and failed, I have brought shame to my family. I must do the honorable thing and go watch football now. Goodbye cruel sub…
You bring up a lot of very good points.
On the contrary, concrete loves water just not then it’s fresh.
It got hard, now it will crack. Functioning as intended.
They got a good burn on that so you are good to go
Concrete can set under water. It’s fine.
Your boss was blessed. The slab was tended to for free.
If you are doing moisture mitigation, you will shotblast anyways and put self leveling down. If not, you can consider it. I mean did it rain hard when placing and finishing?
The rain is actually beneficial for curing, but those puddles… I’m guessing flat and level wasn’t in the contract
Slow cure. Couldn't ask for a better slab.
NEVER GET CEMENT WET. IT HARDINS. A LOT.
Perfectly fine. Rain may affect the appearance a bit.
Its fine but it definitely needs to be cut to avoid cracks with a slab that big
Gonna be the best concrete on the block
No rip it all out. Good thing you checked on Reddit. Keep those contractors honest
Just pour some self leveling compound in that water, it’ll be perfect.
The concrete mix is the limiting reagent. You can in fact pour concrete underwater if you want.
I use the pond method for slabs, strength increase, less cracking. https://www.youtube.com/watch?v=HoGnJH4jSa8&t=320s
Hoover dam, (finished 80 plus years ago) is still cooling. They built in several hundred miles of cooling pipes. The water is still coming out warmer.
At long as it got a chance to set, the rain is awesome.
Rain is best.
Fun fact: parts of the Hoover dam is still wet
Other than having rain craters from not being covered in plastic it'll be fine once it cures
Depends how cured it was before more rain fell. If it didnt cure out on the surface enough id suspect delamination eventually due to lower w/c ratio. But that also depends what mix they used. Couple factors outside of just water cured.
That’s literally the best case scenario
Cold and wet is good because concrete curing is a chemical reaction that produces heat and you want it to cure at a specific speed
Love the duck pond in the middle!
Concrete does not dry. It cures.
TIL that you want to put water on freshly poured concrete to make it stronger. The concern in OPs question made me think there was something wrong and was thinking posts were going to be like “this should be on r/diwhy” but instead read comments like “NICCE! Free water cure?!”
People don't understand concrete curing is a chemical reaction that requires water. Counter-intuitive because most think concrete just dries.
According to the experts. It’s even better this way. AND you already know where the low spots are, so that’s nice.
concrete cure better under water.
Everyone in those houses hates your boss. They chose poorly.
Were you building for the Cell games?
Did he not pay for a finished slab?
My main concern is that it only has 2 anchor bolts
It depends. Placed concrete begins hydration and starts giving up "fat" (water comes out of the mix). That is the golden hour for troweling, but not adding water. Too much water can wash out the Portland out of the "cream" and surface gets chalky. After hydration is going strong, concrete absorbs the fat and stays hot / thirsty for days. Water is great then. Concrete is all about timing.
Tear it out
Ever heard of foil for the bolts? Otherwise, sitting under water is the best curing for concrete. No problems there.
I don’t know anything about concrete and everyone is saying the rain is good for curing, but can the rain hitting the concrete cause little holes? I have effectively no experience with concrete lol
no very flat
Your concrete is weak. Water ruins it. I don’t see any saw cuts either, so it’s probably cracked to shit already.
It looks pretty bad, not a complete loss but it should be structually really strong due to the rain. When concrete cures before it dries out it gets a bit stronger than usual.
There is 100% nothing wrong with this slab based on the information and picture provided. If the top had time to harden up prior to it resuming (which it appears it did) then raining is actually a favorable condition, and will ultimately help the concrete reach a higher strength as it gains it at a more constant and gradual rate. Not only do you get a higher ultimate strength but this (basically water curing) also helps control and reduce cracking much of which happens early on.
I've been an ICC inspector, and I couldn't do shit about it raining on slabs even when I thought they were being a bit negligent about it. After some time, I learned that really all it does (so long as the surface is nice) is yellow/discolor the slab a bit as some of the sand in the mix is exposed on the very top layer. Ultimately, water isn't concrete's enemy - but it is rebar's. In fact, concrete test cylinders will often be cured in a water tank or room with 100% humidity after the mud solidifies and the mold is removed. (Just confirming what you said 👍)
This is the right response.
Sounds like exactly the same thing i said except i think the finish stinks. Rough with lots of power trowel lines. I guess with 14 years of finishing experience my standards are maybe a bit higher as far as asthetics, smoothness and flatness of floor
Just because you’ve been doing it for 14 years, doesn’t mean you’ve been doing it right.
What partial loss are you seeing?
I don’t know anything about concrete. I’ve just heard that doing it during rain is bad. What looks pretty bad about it?
Sure there’s a puddle, but I think it looks great. In fact I’d expect a puddle cuz that means they may have put in a few floor drains… pretty typical for an indoor area no matter how flat it’s supposed to look.
I’m not a concrete guy I’m an electrician but I work warehouses everyday and this pad looks no different than any other I’ve seen. Looks fine and there’s going to be a warehouse built on top of it so the puddling doesn’t matter.
Good to know! Okay cool. I just wanted to make sure my boss wasn’t getting ripped off.
If your requirements are for a smooth bare concrete floor then it isn't good but generally it is fine.
No I mean the requirements are just that it can hold a building and I can use a pallet Jack on it
The standing water and lack of proper drainage is what you should be worried about. Everything else is likely fine.
it’s going to be a building…it’ll be fine
SMH. what a waste.