oceanobob
Senior Member
Existing 5000 sf warehouse floor to be removed and replaced. Floor is concrete over wood. Wood framing similar in concept to a raised floor house with 2x joists, cripple walls in most of it, although wood girders in one section. Has perimeter concrete foundation and interior grade beams; both short stem wall shape. Due to vintage, flooring sheathing is two layers of 1x. No plywood. A wire mesh reinforced concrete was placed directly on the wood. We figure concrete to be about 50 yrs ago, give or take. Wood is dry rotted and many repairs conducted over the years. This 'repair' is to remove everything and fill, then place a new concrete floor. Initial actions were to brace the roof and walls in sequence and replace the oortion of the perimeter walls to the floor elevation with either grouted CMU or cast in place concrete. Then cut through the dock to gain access to the inside and remove the old materials. Trials were conducted on the concrete removal process: sawing it to make squares and pulling it up with a quick bolt/chain/etc accomplishes the separation although the sheathing sticks to the concrete. Sending the concrete to the recycle with this amount of wood is a no no, so the decision to cobble the concrete squares by working the hammer atop the existing slab achieves quite a bit of separation, and the cobbles sent to the bottom of the approximate 5 foot fill for "permanent storage". The wood removal goes equally slow as it is so rotted it falls apart mostly but occasionally there are members which require sawzall etc. Walking on the sheathing after a square cube of concrete is removed will get you a leg down and maybe a rusty nail bite LOL. The wood gets smashed up and dismantled with the reachlift, then hauled out with the forklifts and bins to go into the rolloff containers. Some of the above is shown in pics. Seems the overall process has become concrete removal & cobble, then the wood removed to make a hole to place the concrete. Process is sort of iterative in lieu of sequenced. One bay is almost done in the pics. For those of you who work in soil with cobbles, maybe a comment please. I could speed up the process by concentrating efforts on removing all the concrete, rubble it, then place & mix it in lifts in the one section that is completed that you see in the pics (dump truck hauls the fill inside and the skip spreads it, reachlift and skip wheel roll is compaction on this lift and the sheepsfoot ride on compactor will be next (just to make sure and get the edges better) prior to any more fill (am about 15" filled of rubble and soil, just enough to cover the interior grade beams & rubble so we could drive the reachlift and dumptruck). The fill is inert (minimal clay) sandy loam, mostly sand. Fill is pre-conditioned with moisture prior to hauling it into the building.
My Question: Unsuredness is holding me from bringing the concrete rubble 'too high in the fill' - but if I could mix all the concrete in this one bay/section, then I could attack the balance of the wood all at once with a midi ex and a thumb then hire a crew for a couple days to load the roll offs with that wood. Then I could 'get after it' for the balance of the fill and the new 6" slab. Any suggestions on getting good compactible subgrade with these cobbles? Size ranges from less than a square foot to a few at 18 by 12 by 4 thick with one or two at 18 by 18 by 4 thick. Would you fear having a compaction job with mixed materials? I would hazard a guess and say it will take about 3 feet of mixed fill (ie sand w cobbles) depending on the ratio to get a home for the concrete in this first bay. That would give me 18" of sandy material with no cobbles and 6" or so of Cl II base under the slab. Never worked much with mixed fill as am usually in pure sandbox style soil where we remove, moisture condition, and replace. Regarding how to deal with cobbles - does 'engineering opinion' allow these cobbles "back in the ditch/fill" or are they always to be screened away? We simply can not take this concrete to the recycle since there is just enough wood stuck to it to make it rejectable but not enough wood to allow it for fill due to organic less then 2%. There are no pipes or conduits, only the fill with the concrete atop.
My Question: Unsuredness is holding me from bringing the concrete rubble 'too high in the fill' - but if I could mix all the concrete in this one bay/section, then I could attack the balance of the wood all at once with a midi ex and a thumb then hire a crew for a couple days to load the roll offs with that wood. Then I could 'get after it' for the balance of the fill and the new 6" slab. Any suggestions on getting good compactible subgrade with these cobbles? Size ranges from less than a square foot to a few at 18 by 12 by 4 thick with one or two at 18 by 18 by 4 thick. Would you fear having a compaction job with mixed materials? I would hazard a guess and say it will take about 3 feet of mixed fill (ie sand w cobbles) depending on the ratio to get a home for the concrete in this first bay. That would give me 18" of sandy material with no cobbles and 6" or so of Cl II base under the slab. Never worked much with mixed fill as am usually in pure sandbox style soil where we remove, moisture condition, and replace. Regarding how to deal with cobbles - does 'engineering opinion' allow these cobbles "back in the ditch/fill" or are they always to be screened away? We simply can not take this concrete to the recycle since there is just enough wood stuck to it to make it rejectable but not enough wood to allow it for fill due to organic less then 2%. There are no pipes or conduits, only the fill with the concrete atop.