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-   -   Huge Trench in Basement Floor (http://www.diychatroom.com/f19/huge-trench-basement-floor-146698/)

martin1410 06-11-2012 08:47 AM

Huge Trench in Basement Floor
 
Hey!

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.

Thanks!

TarheelTerp 06-11-2012 08:56 AM

Quote:

Originally Posted by martin1410 (Post 940853)
What do I fill it in with? Gravel and sand? Concrete? Gravel and Concrete? Gravel, sand, and concrete? What do I do.

If you happen to have a pile of any of those handy... sure.
I've always used the pile of dirt that was right next to the trench.

martin1410 06-11-2012 09:10 AM

oh.



really? and then just concrete for make a flat floor?

jcarlilesiu 06-11-2012 09:39 AM

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.

martin1410 06-11-2012 09:51 AM

Dowel in? What does that mean?

jcarlilesiu 06-11-2012 09:55 AM

Quote:

Originally Posted by martin1410 (Post 940883)
Dowel in? What does that mean?

http://www.pavingexpert.com/images/c...e/expjnt02.gif

http://www.pavingexpert.com/concjnt1.htm

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.

martin1410 06-11-2012 10:03 AM

Aggregate and dowels can be found...where?

Home Depot?

Martin

jcarlilesiu 06-11-2012 10:09 AM

Quote:

Originally Posted by martin1410 (Post 940887)
Aggregate and dowels can be found...where?

Home Depot?

Martin

Yup.

CA6 fill would be cheaper to be ordered from a materials company who can deliver it to your drive way. You simply need to figure out how much cubic feet of fill you need.

When they trenched the basement floor, what did they pull out under the slab? If its clean gravel, and they saved it, I don't see any reason why you wouldn't be able to reuse it.

As far as welded wire fabric (reinforcing), and rebar, both of those can be found at your local home improvement store. You will have to drill the existing slab edge for the new dowels. Place them in the drill holes loose, and then set the other end in the wet concrete.

martin1410 06-11-2012 10:12 AM

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?

Martin

jcarlilesiu 06-11-2012 10:17 AM

Quote:

Originally Posted by martin1410 (Post 940894)
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?

Martin

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.

M3 Pete 06-11-2012 11:09 AM

Quote:

Originally Posted by martin1410 (Post 940887)
Aggregate and dowels can be found...where?

Home Depot?

Martin

"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.

jcarlilesiu 06-11-2012 11:20 AM

Quote:

Originally Posted by M3 Pete (Post 940918)
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.

The dowels shouldn't be connected at both sides (meaning new and existing). Due to different locations and expansion/contraction characteristics, and because of normal shrinkage cracking, movement should be allowed in the horizontal direction.

The dowels are only installed to stop vertical movement (settling or heaving), and thus the rods don't need to be epoxied to stop this movement.

You are right that in a small trench, the free movement on the dowels probably isn't a big deal as it would be on a large pour. But no since in spending the money on epoxy since it doesn't serve a purpose.

martin1410 06-11-2012 12:26 PM

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?

Martin

martin1410 06-11-2012 12:34 PM

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.

Thoughts?

Martin

jcarlilesiu 06-11-2012 03:03 PM

Quote:

Originally Posted by martin1410 (Post 940956)
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.

That is actually grout.

Use concrete, which is a mixture of some of the ingredients in the product above with aggregate (sand and gravel).

http://www.homedepot.com/webapp/wcs/...specifications

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.

Quote:

Originally Posted by martin1410 (Post 940956)
And the concrete slab should be about 7 inches thick, according to the drawing above?

That drawing was just to illustrate the doweling technique. Match the current slab thickness.


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