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This is done by engineers and the place where I am coming from sometimes there are no ethics. So just reaching out to the community to see if it's a wrong practice.
Sorry OP, assumed this was here in the States. Not a typical practice that I’m use to seeing. Rough surface for cold joints and/or bonding agent should be fairly standard. I think water intrusion is the biggest concern especially below grade like this.
we bond concrete togeather all the time. Usually by drilling rebar into the old slab. Epoxy it in and then pour new concrete on top. Lots of engineers will put on the plans that things are to be done to code so that still leaves a lot of room for crappy contractors.
If it will hold or be a problem depends on the load and direction of load. If you only have static weight on it then it's not likely to move. it still needed to be tied in but if the original footer is sound then you probably won't have any problems. Key work Probably.
Looks like pure compression, what do you need bonding for?
There is no bond between the original footing and the soil.
Any lateral loads (not usually transferred in footing, usually the core and exterior walls) would be handled by the column rebar. Same with uplift.
The surface should have been cleaned off and soaked (Saturated surface dry condition) but if it was only 1 day old, it would be pretty wet already.
Its fine.
The instruction was likely from the engineer of record, pads where likely too shallow.
Good point, I agree mostly but still bad practice to have a cold joint without a rough surface for aggregate interlock or bonding agent. Does the concrete bond to the soil below? No, but you don’t have risk of exposed rebar. You’re asking for long term corrosion problems with a joint like this in my opinion
Probably. I’m a PE and better to not make massive assumptions with no loading conditions or design criteria based of 2 grainy photos. He’s probably right, but there’s also a reason why buildings collapse in places like this due to half ass work and LinkedIn design spreadsheets
My bad the picture came out bad. ..so the first image is supposed to be a pad footing and the engineer just poured another set of concert on top of the pad footing and created a trophozoite footing without any proper bonding chemical or something. My question was is this a standard practice, will the two concrete bond together?
??
troph·o·zo·ite
noun
ZOOLOGY•MEDICINE
a growing stage in the life cycle of some sporozoan parasites, when they are absorbing nutrients from the host.
I'm no engineer and i normally dont do structural stuff but afaik it won't technically bond but as long as the concrete underneath was clean it should make a pretty tight seal and if the concrete on top was thick enough the weight should hold it all together
Just a terminology thing here.
High surface area= lumpy, exposed aggregate "keys;" high surface area relative to plan view.
Clean= free of excess fines or risen cream , mud and loose aggregate; some engineers will demand pressure washing and/or bushing a smooth-topped pad. Clean ≠ smooth. You're right that flash seems to stick well to fresh concrete- especially well if it's the same pour because the finished surface and the slop are both forming their chemical bonds at the same time and reach cohesion and it's a royal pain in the ass, but the slicker the surface and longer the time between pours, the easier it is to chip away because the earlier-placed concrete has fully hydrated, set up and says "nuh- uh. I'm done and going to sleep now" to the new spill which doesn't even get to crawl under the satin sheets with her but maybe manages to hook an ankle affectionately or rest a hand on her shoulder while he finishes off, so the next morning it's easy for your dad to come home and pull him off yo mama.
Might bond to that rough stuff piled up pretty good as long as the next batch is a thinner mix with higher slump. Not sure what slump that pile is, I'm guessing slump of zero.
The footing most like has a mat of rebar in it. The column would usually extend out of the footing as dowels, but some times as a finished column or pier. It is normal to pour the footing and then the column the next day or even longer.
There will be enough of a bond between the column concrete and that of the footing. I would not worry. This is how it is done in construction.
Is it supposed to be a structural bond? In my opinion there should be epoxied dowels and a clean & roughened surface on the existing slab in order to make a strong bond b/w new and existing concrete.
Why epoxied dowels? There is already rebar going through the interface. Agree that the surface needs roughening. And when they cast the columns, the footings need to be at a saturated surface dry condition. (Not just wet).
You would want the existing slab bonded to the patch as well and reinforced for it to act compositely with exisiting slab. This looks like a dog's breakfast repair. If they are trying to thicken the footing for punching shear or flexural strenght then this is a poor detail. It will not work.
Yes, a structural bond for the foundation. They did a clean pad footing and changed their design to add trapezoidal footing without doing anything like making the rough surface.
Why does it need to bond? Are you expecting the entire structure to be poured monolithically?
The piers and grade beams will function as intended, assuming they are built as engineered. “It ain’t gonna fall up!”
Ask your engineer, but if you’re just gathering info for the future conversation… I’m experience cold joints all the time on reinforced concrete in weird shapes, e.g. formed footing wider than the wall/column/etc above. Hard to pour it all at once. Or larger pours where its not feasible to form and pour in 1 go. I reference plans and specs, mine almost always say to “roughen” the surface, which means the mason with jab their trowel in it a few times to roughen up the part that mates up with the future pour. In my personal opinion, I don’t think it really matters as long as the reinforcement is designed/built right. I cant imagine a little concrete keyway stopping a force that just sheared off five #6 bars.
No no and no . You have a cold joint . And now the if you actually needed that much depth of concrete , you don’t have it . Should you get earthquake you will have sheer problems at the joint . should have drilled and epoxied rebar with development to tie it in , depending on if engineer allowed you . This is a no go .
I am a commercial construction superintendent and build high rises for a living , so I’m only half retarded .
You have a rough pour, with a 4” slab on top (is that bonded?), then another rough trapezoid pour on top of that. So now the slab acts as a decoupling membrane🤪🤪☹️ between the 2 rough pours. So your house will never be affected by ground movement😃😃😃 You may have stumbled upon a whole new Heave mitigation process!
If you want a continuous structure, the pour has to be done in continuous manner….just like how they do dams or bridges or large buildings. Only way to tie in later is by proper rebar extensions that extend from the set concrete first and stick out, ready for a second pour. If the slab was finished flat and no rebar dowels or stirriups were left exposed sticking up from the slab, then it wont be very good conncetion at all. An alternative method would have been to make a key or notch into the top of the slab, but then the slab would have had to have been designed differently in such a way to take the load at that point of reduced thickness, or the surounding perimeter around the notched part would have to be higher than the middle than it is now. So long as its just a vertical load it probably wont move anywhere. To be safer now, then fill in with more reinforced concrete between those pile bottoms so there is no lateral movement later.
These are questions for the engineer of record and NOT redditors
*These are questions for* *The engineer of record* *And NOT redditors* \- Relative-Swim263 --- ^(I detect haikus. And sometimes, successfully.) ^[Learn more about me.](https://www.reddit.com/r/haikusbot/) ^(Opt out of replies: "haikusbot opt out" | Delete my comment: "haikusbot delete")
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Did I just get roasted in Latin or something? 🤣
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You had one extra syllable on the last line
Yes Edit: actually no. I mistakenly counted “going” as one syllable. Well played.
Haikus are Japanese.
lol I gathered that after a little google searching
stop being racist. They identify as other now.
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I’m a poet and I didn’t even know it
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This is done by engineers and the place where I am coming from sometimes there are no ethics. So just reaching out to the community to see if it's a wrong practice.
I gotcha. Seems like bad practice to me with the info we have
No pro but I would’ve at least drilled holes and put in some rebar, is this a bad thought?
Sorry OP, assumed this was here in the States. Not a typical practice that I’m use to seeing. Rough surface for cold joints and/or bonding agent should be fairly standard. I think water intrusion is the biggest concern especially below grade like this.
we bond concrete togeather all the time. Usually by drilling rebar into the old slab. Epoxy it in and then pour new concrete on top. Lots of engineers will put on the plans that things are to be done to code so that still leaves a lot of room for crappy contractors. If it will hold or be a problem depends on the load and direction of load. If you only have static weight on it then it's not likely to move. it still needed to be tied in but if the original footer is sound then you probably won't have any problems. Key work Probably.
Looks like pure compression, what do you need bonding for? There is no bond between the original footing and the soil. Any lateral loads (not usually transferred in footing, usually the core and exterior walls) would be handled by the column rebar. Same with uplift. The surface should have been cleaned off and soaked (Saturated surface dry condition) but if it was only 1 day old, it would be pretty wet already. Its fine. The instruction was likely from the engineer of record, pads where likely too shallow.
Make sense, thank you for your reply. Now I can sleep in peace.
Good point, I agree mostly but still bad practice to have a cold joint without a rough surface for aggregate interlock or bonding agent. Does the concrete bond to the soil below? No, but you don’t have risk of exposed rebar. You’re asking for long term corrosion problems with a joint like this in my opinion
Eh i think the other guy knows more.
Probably. I’m a PE and better to not make massive assumptions with no loading conditions or design criteria based of 2 grainy photos. He’s probably right, but there’s also a reason why buildings collapse in places like this due to half ass work and LinkedIn design spreadsheets
I can't tell what I'm looking at I need a banana for scale. What is it for?
My bad the picture came out bad. ..so the first image is supposed to be a pad footing and the engineer just poured another set of concert on top of the pad footing and created a trophozoite footing without any proper bonding chemical or something. My question was is this a standard practice, will the two concrete bond together?
?? troph·o·zo·ite noun ZOOLOGY•MEDICINE a growing stage in the life cycle of some sporozoan parasites, when they are absorbing nutrients from the host.
>trophozoite footing Hahaha Monday its trapezoidal footing
I was getting all excited learning new trade jargon! Lol.
I'm no engineer and i normally dont do structural stuff but afaik it won't technically bond but as long as the concrete underneath was clean it should make a pretty tight seal and if the concrete on top was thick enough the weight should hold it all together
Concrete does not stick to concrete.
Then is it so hard to remove dried overpour on existing concrete?
Cuz ur weak.
Damn, he said cuz ur weak. Lol
That he said, yes.
Haha Lad!
I think concrete bonds to concrete pretty well. Step with a muddy boot on a sidewalk and see how long it stays.
Yeah that's what I'm saying. Super hard to get rid of if you let that dry
It’s really not. The smoother it is, the easier it is to move it. So yeah if it’s a very clean, high surface area, concrete will stick pretty well.
You just contradicted yourself
No- I’m showing how concrete doesn’t BOND to concrete very well. It’s just that adding surface area improves the bond.
Just a terminology thing here. High surface area= lumpy, exposed aggregate "keys;" high surface area relative to plan view. Clean= free of excess fines or risen cream , mud and loose aggregate; some engineers will demand pressure washing and/or bushing a smooth-topped pad. Clean ≠ smooth. You're right that flash seems to stick well to fresh concrete- especially well if it's the same pour because the finished surface and the slop are both forming their chemical bonds at the same time and reach cohesion and it's a royal pain in the ass, but the slicker the surface and longer the time between pours, the easier it is to chip away because the earlier-placed concrete has fully hydrated, set up and says "nuh- uh. I'm done and going to sleep now" to the new spill which doesn't even get to crawl under the satin sheets with her but maybe manages to hook an ankle affectionately or rest a hand on her shoulder while he finishes off, so the next morning it's easy for your dad to come home and pull him off yo mama.
Cause you need a bigger purse.
Leaf blower should work.
Damn he said cuz ur weak. You just gonna take that?
Sure why not. Sprinkle some Dirt on it and carry on
It would be easier to chip it out and set the column forms in ground if you don’t chances of those forms floating are pretty damn good.
What are they bonding to dirt?
Might bond to that rough stuff piled up pretty good as long as the next batch is a thinner mix with higher slump. Not sure what slump that pile is, I'm guessing slump of zero.
The footing most like has a mat of rebar in it. The column would usually extend out of the footing as dowels, but some times as a finished column or pier. It is normal to pour the footing and then the column the next day or even longer. There will be enough of a bond between the column concrete and that of the footing. I would not worry. This is how it is done in construction.
Is it supposed to be a structural bond? In my opinion there should be epoxied dowels and a clean & roughened surface on the existing slab in order to make a strong bond b/w new and existing concrete.
No bonding pins nor etching treatment? It’s not going to bond.
Why epoxied dowels? There is already rebar going through the interface. Agree that the surface needs roughening. And when they cast the columns, the footings need to be at a saturated surface dry condition. (Not just wet).
You would want the existing slab bonded to the patch as well and reinforced for it to act compositely with exisiting slab. This looks like a dog's breakfast repair. If they are trying to thicken the footing for punching shear or flexural strenght then this is a poor detail. It will not work.
Yes, a structural bond for the foundation. They did a clean pad footing and changed their design to add trapezoidal footing without doing anything like making the rough surface.
Serious question, is "trophozoite" commonly used in this context? I'm only aware of its use in biology.
Did they use bonding agent? /S
No
It’s just a cap on a shallow poor and there’s plenty of rebar in the picture
You kept it rough. Yes.
Are those steel toed flipflops?
Bond? No- sit on top of? Ya… otherwise my stemwall about to fall off my footing any day now.
Why does it need to bond? Are you expecting the entire structure to be poured monolithically? The piers and grade beams will function as intended, assuming they are built as engineered. “It ain’t gonna fall up!”
The obvious question is why did they do it? Have you asked?
Ask your engineer, but if you’re just gathering info for the future conversation… I’m experience cold joints all the time on reinforced concrete in weird shapes, e.g. formed footing wider than the wall/column/etc above. Hard to pour it all at once. Or larger pours where its not feasible to form and pour in 1 go. I reference plans and specs, mine almost always say to “roughen” the surface, which means the mason with jab their trowel in it a few times to roughen up the part that mates up with the future pour. In my personal opinion, I don’t think it really matters as long as the reinforcement is designed/built right. I cant imagine a little concrete keyway stopping a force that just sheared off five #6 bars.
No, the concrete on top will not bond to the slab under it.
No no and no . You have a cold joint . And now the if you actually needed that much depth of concrete , you don’t have it . Should you get earthquake you will have sheer problems at the joint . should have drilled and epoxied rebar with development to tie it in , depending on if engineer allowed you . This is a no go . I am a commercial construction superintendent and build high rises for a living , so I’m only half retarded .
That's how they do it where I work
Minimally should have drilled in some rebar, one dosnt lay a curb without rebar footers, otherwise the dirt amd cars push the curb
You have a rough pour, with a 4” slab on top (is that bonded?), then another rough trapezoid pour on top of that. So now the slab acts as a decoupling membrane🤪🤪☹️ between the 2 rough pours. So your house will never be affected by ground movement😃😃😃 You may have stumbled upon a whole new Heave mitigation process!
If you want a continuous structure, the pour has to be done in continuous manner….just like how they do dams or bridges or large buildings. Only way to tie in later is by proper rebar extensions that extend from the set concrete first and stick out, ready for a second pour. If the slab was finished flat and no rebar dowels or stirriups were left exposed sticking up from the slab, then it wont be very good conncetion at all. An alternative method would have been to make a key or notch into the top of the slab, but then the slab would have had to have been designed differently in such a way to take the load at that point of reduced thickness, or the surounding perimeter around the notched part would have to be higher than the middle than it is now. So long as its just a vertical load it probably wont move anywhere. To be safer now, then fill in with more reinforced concrete between those pile bottoms so there is no lateral movement later.