request recommendations for rebar spacing for concrete project

[RDrancher]

I'm not a fan of fiber, but it doesn't hurt anything if you want it.

I am a big fan of rebar. It's tried and proven to work.

Most problems with concrete are from the dirt settling after the concrete has cured and leaving a void under the slab. It's extremely important to have your dirt compacted!!! The other problems come from too much water in the mix. Some contractors will add water to the mix so it flows better and makes their job easier. For maximum strength, you want as little water in the mix as possible. It wont matter what the rating is, if you have too much water, it could easily be half of that when cured.

As for spacing, a 2 foot grid is usually plenty. Sometimes I've gone 18 or 16 inches when I have extra rebar, but I don't think it actually does anything measurable adding extra rebar to the grid on a flat slab.

Having a footer where the vehicle transitions onto the slab and doubling up on the concrete is important. I've never used anything bigger then half inch, also called #4. It wouldn't hurt to use 5/8's at your footing, but there isn't any real advantage on your pad area.

Eddie

Agree completely. Oversizing rebar in a slab can lead to surface cracking. In thirty years of pouring concrete I used the following with excellent results. 3.5-4" thickness - #3 with a continuous #4 perimeter bar tied to the bottom of the #3 in a thickened edge. 5.5-6" thickness - #4 with either #4 or #5 perimeter bar.

One joint should be enough. I also agree, don't tie the new into the old. If the old was thicker, it would be OK to tie to two together.

I also agree, no plastic under it, that is more of a indoor application, like under a garage floor.

We often break the test cylinders at 7 days and or 14 days. 7 days is if we want to open a road right away. Usually we consider most concrete cured enough after 14 days to put it in service.

You can also spray the concrete with a curing compound so you don't have to try and keep it wet.

I'll only disagree with one point. I always tied slabs together by epoxy doweling with #3 or #4 depending on the thickness. A small hammer drill with a fast vibration is pretty easy to control without cracking the edge on 4" slabs. On foundation to exterior slab tie-ins I would dowel (with slightly oversize holes), but didn't use epoxy since the dowels were mostly to help control vertical movement. A 4" slab will move more than a foundation during cold/heat changes.

I was also a big fan of Deck-o-foam expansion joints with a tear-away top piece and Deck-o-seal between exterior slab/foundations.