So in order to put in a new pipes in our basement, we had to big up a huge trench in our basement floor. It is around 12 feet long, 2-3 feet wide, and a 1-2 feet deep. (I'm estimating, I didn't dig it, nor am I looking at it right now.)
What do I fill it in with? Gravel and sand? Concrete? Gravel and Concrete? Gravel, sand, and concrete? What do I do.
To be completely honest, I understand the reasoning behind the rebarb, but that sounds like over kill to me. Am I just being a newbie? I am overseeing the remodeling of this house for men and women coming home from incarceration, and I'm not certain, I know any volunteer with a huge masonry bit and the experience to use it.
If there will be a delay between completing the pipe work and inspection... then a bed of more easily moved gravel could prove to be nice to have.
But... unless the floor is going to have some other non residential use, one that I haven't seen described here with weight loads which might require that sort of reinforcement... rebar and epoxies and grout and all the rest is indeed overkill.
Soil carefully laid in and well tamped is plenty good enough.
Concrete slab should be re-installed on a bed of compacted CA6 aggregate or similar product with compaction qualities.
To prevent heaving or settling of the slab, it would also be a good idea to dowel in the new slab to the old. If you ever plan on finishing the basement or putting down flooring, I would highly recommend this to avoid future issues.
These dowels in the edges of the existing slab will prevent the slab from heaving or settling differently than the existing slab.
In a monolithic pour, the concrete is all unified and if any settlement occurs, it occurs as a body. Since a trench has been cut, you have essentially separated this slab, meaning that any settlement in the future may settle at different rates.
If you plan on putting down tile, carpet, or any other flooring system, or if you plan on inhabiting this space, the dowels will bond everything back together so that you don't have to worry about the new trench slab popping up or settling down.
"dowels" in this case are usually #4 rebar (steel reinforcing bar) cut to the right length. Not wooden dowels.
And I've always heard they were to be epoxied into the existing slab, not left free like shown in that link. I think that may be more applicable to paving rather than residential slabs.
Wow, okay awesome. The "gravel" they pulled out from the trench is mostly red/orange sand-like material, large rocks, and clubs of gravel stuck together with concrete. We still have it. It has been sitting outside for a month or two. Would you use that?
The biggest issue with the base that you use is compaction.
For instance, using a silty soil that is very organic can lead to terrible settling. A concrete slab on grade is not able to span, thus its only as strong as its base. If the base settles, the concrete will settle as well.
Sand is not a terrible base as it drains well, but doesn't compact well.
If you don't see a bunch of settlement cracks or other indications of movement of the existing slab, the base may be fine. Its a judgement call without expensive testing.
Okay, so it sounds like either I use the stuff that was in the hole and then pour concrete on top to make a level floor--pour a slab. Or I use something like this product to fill in the hole and then pour concrete on top.
And the concrete slab should be about 7 inches thick, according to the drawing above?
Okay, so it sounds like either I use the stuff that was in the hole and then pour concrete on top to make a level floor--pour a slab. Or I use something like this product to fill in the hole and then pour concrete on top.
Depending on how many cubic feet of concrete you need, bagged mixes like this might be a pain. Then again, in a basement application, this might work well.
Concrete reinforcing in a slab application isn't for compressive strength. That is gained from the concrete itself. The reinforcing is mainly a means of keeping the slabs from moving independently of each other over time.
While the pros here are telling you the EXACT correct way to do this, do what Tarheel says a couple posts above. Use what came out of the hole, being sure to tamper it in many stages along the way.
Last I checked this was the "DIY Home Improvement Forum", not the "Professional Concrete Flooring Forum".
Thank you for offering your professional opinion, but don't get pissy when it is pointed out how much overkill it is.
OP, you can do what the experts say and be 100% you will never have a problem, over do what Tarheel says and only be 99.5% sure that you will never have a problem. It is your time and money. You make the call.
Remodeling a house for men and women coming home from incarceration is not a normal DIY home improvement.
The Pros giving their advise on how to do it right probably already have seen the outcome of skipping proper technique/procedure.
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