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HighDesertHomeOwner 11-24-2010 12:10 PM

The use of river rock and broken concrete bits
as filler to reduce the concrete volume needed, I mean.

I am talking about a slab floor construction common or standard in Southern Cal newer homes, not concrete foundation with floor joists.

There are a lot of give away broken concrete pieces and river rock. Can I use them to fill the concrete slab?

My thinking is that it is OK as long as the pieces and river rock are small, say 3" thick and 4-5" in other dimensions, or smaller, and using them in the middle non-weight bearing section of the slab.

The weight bearing sections (perimeter) of the concrete slab will not have such filler.

Any opinion. I found it hard to believe that such filler will "sink" later once the slab has cured.

Also I plan to add such (the smallest) pieces 3" or smaller into the cement mixer and not just pour concrete mix over the filler pieces. I think this way the fillers with adhere to the concrete better. Will the mixer take it without falling apart? Mine is a small 3.25 cu feet mixer.


granite-girl 11-24-2010 02:15 PM

Kinda sounds cool. What kind of area are you talking about & how big ? Pictures would be great when you are finished..... that is if the powers that be on here say it can be done.
Good Luck

inspectorD 11-24-2010 06:10 PM

I would suggest trying a "test Patio" before you do it. Usually anything up to 3 inches is the limit for aggreagate size, it all depends on your mixture. The stuff from the yards (professional) has 3/4 rock unless you specifiy different.
Try for a mix that is able to be built into a baseball type consistency, this tends to have less water and more portland mix. This should create a higher strenth PSI concrete. The reason is you want to be over 2500, but with a mixer this is hard to guage if you have not done this before.

These are some concrete folks around, they may chime in too, just my:2cents:

itsreallyconc 11-27-2010 05:52 AM

don't be a cheapskate,,, by the time you hustle about finding broken conc you'll have wasted more time, gas, & vehicle wear & tear than you've saved,,, river stone's smooth - not a good candidate for inclusion into conc UNLESS you're 'seeding' it into the top for a decorative effect.

its impossible to duplicate the quality of conc from anyone's redi-mix plant so why anyone needs to mix their own mud's usually beyond me but understand economics of small deliveries from plants.

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