Concrete Joints

Concrete Joints

G’day welcome back to Buildsum this time I want to show you three joints that we commonly use when we pour concrete Just to explain what I’ve got drawn here. I’ve got two brick Walls Which represent the outside of a single building or two buildings doesn’t really matter but a sand bed down to put my concrete on Because this is actually outside That really need to have my membrane But in all that sort of doesn’t matter for this video because I’m just concentrating on the joints now if I was to pour Concrete between these two walls. I’ve got a bit of a problem because concrete does expand it does grow as I say and if it was to grow and it was poured tight between these two walls so no gap here then it would actually start to push and crack these bricks out so the first type of joint I want to show you is an expansion joint so all it is is a piece of Generally about 12mm bituminous Material or they do have a foam Type product as well nowadays thats put between the concrete and the other material this case Brickwork, but it could be steel or something else it could also be another bit of concrete And all that does is when the concrete grows it obviously allows this material will compress and that allows for the expansion and contraction without breaking the opposing material So that’s the first joint is the expansion joint now obviously this is a pretty long bit of concrete and Inevitably you will get cracks appear in your concrete and if we don’t Control them they will just randomly crack across the slab and they’ll look unsightly So what we can use is a Control Joint And all that basically is is we weaken the slab at a point of our choosing and that allows when the slab does crack It gives it a weak point to crack along and because we’ve got a crack or I sorry we’ve got a line In the side there already then the eye doesn’t see the crack and it controls It makes it nice and straight And it just makes it look a whole lot neater so all that that’s just formed with a concrete tool Or nowadays they commonly come back and cut that slab that cut into the slab a couple of days after they’ve poured it But that’s just that Control Joint so we control Where the slab is going to crack Okay, so we’ve had the expansion joint now we’ve got a control joint Now obviously depending on how big your concrete pour there’s only so much concrete we can pour in a day And we may only want to pour a certain amount at one time, so we have to be able to continue and add to our slab without and keep the slab as a single unit the problem is if we pour two slabs of concrete next to side-by-side if For some reason this slab was influenced by the ground pressure or and up and up forcing the ground it can move up and down without Affecting this slab, so it’s just going to move on its own And obviously cause a trip hazard can see this with council footpaths and other slabs all the time This slab can move independently of this slab So what we have to do is we have to create well as two ways the first way is a key joint So you can see here the slabs actually got a keyed in profile and that’s created by when we actually go back to pour it put our formwork in we actually put a Key Joint strip on the inside of our formwork so that when the sides poured that profile is created and then that’s removed and The next slab is poured up against it. So now that is those two slabs are keyed together Still got our little joint down, so it looks the same But if this slab now is to get lifted up then it would bring this slab up with it so it probably wouldn’t lift as far, and you wouldn’t get the trip point because those two would stay at the same level, so that’s a Construction Joint This means we can now stop work one day Come back the next day and keep going and keep our slab locked together as 1 unit the other method for a construction joint and in quite often used in conjunction with the key Joint is What we call a dowel joint so we’ve poured this slab let it set for a couple of days and what we do is we go along and drill a series of holes Now the size of the holes the spacing all that sort of stuff would have to be determined by structural engineer when he designs the slab But basically you drill a hole into the slab What you do with the already set slab is you put grease or some other lubricant into the hole and then you insert the dowels into a hole So what’s going to happen is we’re going to pour concrete on this side The concrete on this side will grab and lock on to the dowels but because there’s grease on this side now if the slab Shrinks or moves back that will let the Dowel still slide back and forwards they can’t if the slab lifts up then the other side’s going to come with it, so it lets the Slab it does let the side contract, but it stops it from lifting up unevenly so there we go there is two construction joints a key joint up here and a dowel joint up here Alright, so there we go. There’s three common joints use with concrete expansion Joint the Control Joint and the Construction Joint

Comments (49)

  1. thanks dude you are really a life saver

  2. a lot of cracking is due to curling and differential drying of a slab . would love a video on that. will check out your channel.

  3. i really love your videos. I dont know what program your using but it is very detailed. and even though i know these things its great to see a different perspective. thanks

  4. very detailed n quality video. Thnx!

  5. wow you are like the only person on youtube that helped me understand the different types of joints, thank you

  6. Love and Respect from Pakistan. It clearly washed away my confusions regarding joints.

  7. This video is amazing. Thank you so much for your information. It helps me a lot.

  8. Very informative and easy to understand. Thank you!

  9. what about cold joint

  10. what about a joint that you smoke?

  11. Awesome Well done! Very well explained, Really, really helped. Thanks. Saludos!

  12. your amazing sir thanks million of times. that was exactly the thing i searched about it in many websites but finally, i found it in your video. that was so clear and fantastic explanation i have ever seen it.

  13. ?????? πŸ˜•πŸ˜§πŸ˜¦πŸ˜₯😡😡😡😒😒😒😒😒😷😷😷😷😭😭😭😭😫

  14. I don't think it is always necessary to have an expansion joint on a wall. With expansion joints elsewhere, the wall should be fine.

  15. And its amazing how many professionals ignore the proper spacing and expansion joints. . Thats why you see so many sidewalks are popping and have to be shaved.

  16. love guys for giving a wonder full clarity about joints
    make some more videos that like us engineering students can learn well
    thank you

  17. Q: What's better, Key joint or dowel joint ? Great video btw πŸ™‚

    Q: Does concrete expand, & shrink, even after it's set? or only during the time it's setting ?

  18. Great work. Nicely explained

  19. reinforced concrete joint ,correction please

  20. reinforced concrete construction joint …more know how

  21. we kindly remove the sroove asphalt surface coverings' is concrete and stabilized roadbed compaction problem ..gday po.

  22. All three joints should be used once??

  23. cheers mate , i knew the expansion joint but not the other two , thank you

  24. thanks for the vids really helping my construction management studies !

  25. Amazing Sir

    cleared my concept

  26. Before, I had a hard time distinguishing these joints from one another. But you explained it clearly. Thank you so much!

  27. Thankyou .this was really useful . I watched it day before exam, n i was able to write about it

  28. great video! i keep hearing cold seam be tossed around with concrete…what is that?

  29. Best video on joints …

  30. Thank you so much for your video. I have joined construction recently and there is so much to learn. this video perfectly explained 3 things which I had to familiarise with at one 6 minutes long video. Saved me so much time.

  31. Thank you. you are amazing

  32. Thank you so much for your awesome video

  33. Is it a construction joint or contraction joint?

  34. 2:11 Dummy Joint.

    3:49 Tongue and Groove Wrap Joint.

  35. Its really nice video out of all. Thank you for the video. but there are a couple of questions need to be clarified 1) Is expansion joint only be at the edges? If the foam board is kept at the middle of the panel then is it called an expansion joint
    2) Is it Reinforced concrete slab or concrete slab, if reinforced concrete slab then how the steel bars will be placed ?

    Please explain this questions. Thank you

  36. Hi Buildsum,

    Thankyou for that very informative video. The only issue I have understanding the joints used in construciton is now is that surrounding the 'Isolation joint' what is the difference between these joints you have explained and the isolation joint?



  38. Thank you for your videos, I now understand so much more and have learnt lots. A question if I may, in an area where I can not get a cement truck and can only mix by cement mixer, a slab on ground with side footings that go into ground, as in your slab on ground video, it will be impossible to pour the full slab in one day. I wish to use the key joint method , my question is do I do each section with edge footing, or do I do the whole edge/footing first then the slab on top, also not so sure how i will do the key joint with the mesh layed out. Any advice would be great and thanks again.

  39. Thank you very much Sir. Very simple and clean expalnation of a subject I am having trouble with. God bless.

  40. best illustrative and laminated video in you tube. keep it up

  41. Simply amazing.. full pavement class i was sitting without knowing wt am i learning? 😡😡😡

  42. Thanks, very informative

  43. Your videos are great mate, keep it up.

  44. Hi Buildsum, how can you tell visually if something is a control joint or a construction joint if you're inspecting a finished concrete floor say in a warehouse?

  45. great video, thanks a lot !

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