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Discussion Starter · #1 ·
I'm in the process of building a fishing/boat dock. I want to build the deck with pouring pre cast concrete slab. I currently building the pilings out of concrete which are turning out Great. The piles are 10' apart so I want to span with a pre cast slab. I will build forms that will give a finished dimension of 45"wide 10' long and 5-1/2" thick I will place 6 1/2" rebars starting 2" from each side and then every 8" apart. I am wondering will the pre cast concrete slab span the distance of 10' and support foot traffic. Any help or ideas.
Thanks
PS had a wooden pier before looking for something that will outlast me
 

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JUSTA MEMBER
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I believe that you need more reinforcement.

Adding a wire mesh over the planned re-bar, would be better.

Have you did the calculation of the weight of this ?

There is tons of force on the center, and concrete has lots of compression strength, but is surprisingly weak in the tensile stretching area.

Commercial pre-stressed things are just that, they stretch the reinforcement, then pour the slab, and wait for curing, then release the reinforcement tension, which pulls the thing together tightly.

Think about installing I beams, or RR track, from pier to pier, as a support for your design.


ED
 

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You need a reinforced concrete (or precast concrete) slab designed. The 'that looks about right' approach to reinforcing the slab is a recipe for a fatally catastrophic failure. The slab needs the right concrete strength and the proper amount of reinforcing with the proper effective depth, with adequate development length. You need a structural engineer to design the system.
 

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When we built our house 30 + years ago on grade concrete slab with a basement we were limited to a basement 14 ft. x any length with 8" thick concrete over that area and #4 rebar on a 12"x12" grid.



Has it survived any weight? You bet it has, some heavy weights. Would i do it again, in a heartbeat? Just do it, it'll be just fine unless someone convinces you to pour it stiff ( like these pitiful pictures ) so the mix isn't weakened.


Mix it with a slump a concrete pumper can pump and you'll be just fine. And if you don't have a vibrator spend some time vibrating the form sides with a hammer. You can't over do that with a hammer.:biggrin2:


Years ago i built myself a soil plate compactor and then i discovered it worked real well as a jitterbug.


EDIT: EDIT:


EDIT: EDIT:
 

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When we built our house 30 + years ago on grade concrete slab with a basement we were limited to a basement 14 ft. x any length with 8" thick concrete over that area and #4 rebar on a 12"x12" grid.

A slab supported by walls is not the same as a slab supported on discrete piers. Neither is a slab that is braced by other structure and the ground the same as a suspended slab that is not. The OP needs a design by someone qualified, not a 'this is what I did and it ain't fallen down yet'.
 

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When you have an engineer design it have him look at Fiberglass Rebar
V. Rod They won't rust.
I got mine from Concrete Protection Products. Inc.
Also they have a Canada, Phone # 418-335-3202 Thetford Mines, QC G6G 6Z5
 

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I'm jealous. I have a lot on fresh water here in Maine and no way would they permit any dock or pier built out of concrete and i believe the same applies for salt water shoreline.

Good luck, hope there are no approval issues. One on the coast recently had to be removed, no link.

Bud
 

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Hammered Thumb
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Salt water is a good catch. Also the fiberglass rebar, if you don't want to use epoxy coated. Should have rebar both ways. Hope you have a crane, though I think it will be just the one slab so 45" wide pier? My other concerns would be how you are connecting it to the piers, and did you get the piers down deep enough past the muck and considered the heavy weight as well.
 

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Discussion Starter · #12 · (Edited)
Thanks for all the input My pilings were poured on the land in the form of a big H the legs are 14' long x 9.25" x 9.75" with a connecting cross member 48"wide between the legs x11" thick x 18" wide the legs were jetted down to an average of 7.5' below the mud line at 10' center only a couple inches of muck then a mixture of sand and shells. Each piling weighs 3525#. I have a small barge with a A frame handled them with no issues. Sry I don't have a picture I will take some next time I get back to camp. Also the concrete mix is a 3500# mix with fibermesh,plastizer,and a rust inhibitor I used for the piles. So SeniorSitizen you said you poured a span of 14' x ? at 8" thick with a 12"x12" with 1/2" rebar was the rebar a single lay and that's a clear span with no support in the center but was supported around all the sides by sitting on top of a wall? The deck will weigh 26-2700# @ 45"W x 10' L x 5.5" thick they will just sit on the cross members of each pile set I plan to pour 10 sections at a time then move them on site. I have no near by supplier for the fiberglass rebar here in La. but I have done the research on the product and it seams to be a great product. I am still searching though. Again thanks for all the the input and I have searching the web for info and looking at bridge deck construction where the average minimum thickness was 7.5" with rebar grid with spans of 8-9' for highway traffic I felt I would be good at what I was planning to do Guess I'll look for more input.
Thanks
 
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