Alternating Full-Length Rebar Dowels For Stronger Concrete Slabs - Remodeling Tips
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- Опубликовано: 27 авг 2024
- www.homebuildin... Click on this link for more useful information about building foundations and home additions. Every once in a while I get to learn something new and share one of those tips with you. Alternating full-length re-bar for doweling into existing concrete slabs to connect a new slab to a building seems like a great idea and one that could be used by more structural engineers in the future.
im a civil engineer and i would like to point that overlapping a rebar can be treated exactly the same as not overlapped as much as the minimum length is respected and max diameter of stack rebar together is respected too. little science - theory of continuity states that concrete is field with micro cracks so installing rebar gives a math calculation and treatment as ideal without cracks concrete. Than the contact between rebar and concrete is calculated at micro cracks length of the rebar it means - doesn't matter if rebar is smooth or not the bond between concrete and rebar is always grater force than the force what rebar can carry in other words it will snap instead of puling out from concrete. example - reinforced concrete [uses smooth steel and caries 10 time more load]. sry for my eng. its hard from german to adapt. cheers
Thanks a lot for taking the time to share your knowledge, it's always greatly appreciated.
I like the idea, and was toying with it myself recently. There is an issue with the approach of inserting the long rebar, and that is if you intend to use rebar rod into a hole that is drilled to the same OD (which is the ideal way in order to minimize movement, and can even avert the need for epoxy), then you will never be able to knock it in as required. Also, precisely and accurately manipulating rebar at those lengths is not an easy thing to do and I think you might get an inconsistent outcome. Lastly, if you stray off-perpendicular even a fraction when you drill your holes, then your rebar grid is going to be just a bit too funky. But, the thinking is definitely worthwhile imho.
I did a crumbling garage patch of slab for a neighbor a number of years ago. It was small at only a few square feet.
Using a concrete partner saw I cut out the bad spot. Drilled dowel holes in the old slab border and banged short easy-to-work-with rebar into place. I then welded in full-length rebar sections connecting each dowel to its opposite mate. After welding, the rebar mess was one solid weave. We poured the concrete the next day.
It's been years since the repair. Usually two or three times every Summer when folks are out bumping into each other, he'll go, "Still holdin'! There's not even a hint of separation between the old slab and the new pour."
An AC-only tombstone buzz box can be had off Craiglist for $100 or less. And since the welds are going to buried in concrete, they don't have to be all that pretty. A competent DIY'er with a little welding research and a few practice sessions on scrap rebar prior to the real work should be quite capable making the reinforcement truly bomb proof.
Thanks for sharing your story and even though I don't think welding the rebar together is necessary, because I've never seen it required by a structural engineer for small repairs like the one you've suggested, but at the same time who can argue with success.
I sure hope you used ASTM A706 rebar if you welded it.
Narrator: "He did not."
It was a crumbling garage floor patch... The grade of the rebar will not impact the repair in any significant manner.
This procedure is actually used to connect a bridge widening to the existing bridge.
I know this video is old and hopefully I get a reply but how would you do the layout for dowels if you have some holes that will need to be drilled in an angle do you have a formula or technique you can show to always have everything squared off even when there’s no square to measure from
What I usually did was drill one about 1 inch lower to allow for bend and then check to see if it was in correct location, then adjusted and drilled the rest. You can usually bend it to fit it's location.
Would you mind speaking to the distance at which the dowels/rods should be spaced from one another, the depth which they should be drilled into foundation, and also what epoxy you would recommend? Thank you, great presentation!
+T Willey I wish I could, but I'm not a structural engineer. What you're asking will depend upon the type and size of the structure. For example a 12' x 12' room addition might only require #4 rebar space 24 inches on center or a bridge might require three-quarter inch rebar spaced 6 inches on center.
called rebar chairs, you shouldn't put timber into concrete that can't be removed
Another tip: Your lap, meaning when you tie a dowel to a full length bar, the lap length needs to be 30 times the diameter of the bar. IE: #4 bar is half inch so your lap needs to be 15 inches long. So your short dowel should be cut at least 15 inches plus however deep you are inserting it. Safe rule of thumb cut your dowel 3 foot or longer. To answer the alternate suggestion, yes that is what a structual engineer would want to see. 30 years of residential & commercial concrete construction.
+Mike Cole Thanks for the tip and everything I've ever done has been 20 times the diameter, which brings me to a tip I would like to share. This comment is an excellent example of why you can't believe everything you hear and should always validate any information you receive with local building professionals, including structural engineers.
Probably that is excessive case. In order to exclude slab/floor derormation we should work with under-slab layer first: to compress sand till k=0.95, draind the groundwater and use thermoinsulation. If slab or foundation will deform even under light frame house, full-lenght rebar will save nothing. Am i wrong?))
But in slabs between floors it may be usefull.
So how deep should dowel rebar go into the old slab foundation?
Usually between 5 and 15 inches. I made it a little longer than your last question :)
yeah great idea! the crack will be there anyway is the load will be unbalanced over old and new poured slab !easy !is not about that you present here ! is about if the slab will sag or not and the water infiltration and live and dead load is apply to them ! silicone every joint !
Confusing
Good Video
+MrMac5150 Thanks again for watching.
Great video . Can it be use for a roof slab?
I would check with an engineer. Concrete roofs might require more doweling or structural reinforcement.
@@gregvancom thank you . Your input would be highly appreciated 😉
what type of epoxy are you using? can i do it in a overhead slab?
It was a Simpson product, but I'm not sure that it can be used for over head concrete.