Will powerhammer crack slab?

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Getting ready to pour the concrete slab for my shop.  I am worried about my 100 lbs. powerhammer cracking it. Is 4” of concrete enough?  Or should I go to 6” thick?  More money.  I have some ½” thick rubber conveyer belting I was going to use under the hammer.  Say 4 layers.  That would give me 2” of cushioning.Also thinking of using the concrete with the fiberglass threads instead of the reinforcement wire.Thanks for any thoughts.  Chief McgeeLast edited by chief mcgee; 10-04-2007 at 02:12 PM.
Reply:From : http://www.ironkisshammers.com/faq.php#faq_3" Q.   How much special foundation is needed?A. No special foundation is needed with Iron Kiss hammers because they are built so massively. They do not need to be bolted down. A standard installation uses a piece of 1/2" plywood between the base plate of the power hammer and the typical 4" thick concrete floor. The plywood provides just enough cushioning to keep concrete dust from being made. Attached either to the plywood or the concrete floor, an angle iron corral around the baseplate keeps the hammer from eventually twisting away from your treadle foot."They seem to think  4" is OK , speaking as a builder I would certainly beef it up thicker.Maybe 4" will do but what good reason do you have not to put in a few extra cubic feet of concrete? Too much rubber on foundation may influence impact?Concrete is strong in compression but has little tensile strength. In an application like this I would thicken the slab , but more importantly have more steel in the lower half of the slab,say 2/3rds down, and extend pad say 2 foot past size of tool this will cover you for your Zone of contraflecture Keeping in mind min. cover.I have no experience with fiberglass threads  reinforced concrete sorry , have used fibre crete in  2 swimming pools I built ... 1 3/4 high tensile pins mixed into concrete then sprayed ... very strong but had potential problems cracking at areas of different thermal expansion ie joint of water and coping. So be aware of non monolithic reinforcement .Good LuckLast edited by Brett; 10-04-2007 at 03:25 PM.A good guess is better than a bad measurement
Reply:Not to downplay what Brett said but you could PM member DDA52 and ask, he has a ton of experience with concrete.Anything worth doing is worth doing RIGHT
Reply:If you want to go thicker and stronger and you have a good idea where you will locate the power hammer, why not just beef up the thickness and reinforcement in that area?  This way, you get some additional insurance against cracking at very little extra cost.  Perhaps in this area, you could use a double layer of wire mesh for reinforcement (one layer closer to the bottom of the slab and another about 1.5 inches from the top of the slab).Also, you might want to consider embedding some anchor bolts or threadded inserts to bolt the machine down.  Even so, the plywood pad on the concrete is still a good idea.
Reply:The fiberglass additive or ny fiber additive that your supplier is using is only as good as the supplier, and or the contractors credit rating with the supplier.  With that being said the  concrete is far superior to  standard 5 bag floor mix someimes its even 4 bag. ( less than 2000 PSI).  Even if you add 8" of concrete just wher ethe tool will be you or I myself would want 6 bag or more. Problem is you'd have to get a full lead of it. 9yrds this time of year depending on suppliers trucks.   Steel and the fiber will help alot steel needs to be 1.5 to 2" from finished surface.  Load berring pads like for stairs and stantion pads for the I beams  can be 8 bag or the same as the wall material.  Right now from a big flat mans price its about 69.00/yrd for 5 bag, 78/yrd for 6 bag, 8 bag is 87/yrd. and the last time I seen the fiber it was 86/yrd. This are rough prices based here in MI with lots of close quarries and Lafarge near by.( portland supplier).  I can't remeber the exact PSI and specs that the fiber improves but in comercial flooring multi story they use it alot and can poour much thinner.  I hate breaking it up to since it never comes out in big chunks, comes apart like a bunch of dirt in a very sticky spiderweb.   Good luck but I think the hammer should have floor PSI requirement specs as well. Just like the bridgeports and Taurus machines do.  A power floor finisher also helps drive the aggregate down making a stronger surface.500 AMP AIRCO TIG LINCOLN PT185 100% DC @ 128 AMP-WTFSPEED GLASS 9002X MILLER THUNDERBOLT 225HOBBIEST TURNED WELDING JUNKIE8 2ND FIRECAT - SNOWMOBILE RACE CHASSIS FABRICATORPRIDE IS WHAT MAKES YOUR WORK SO GOOD
Reply:Also make sure the earth under it is well compacted since this will be supporting the floor .Me!
Reply:I would suggest that you don't take the risk, Just sell me the powerhammer for cheep........... Sorry I had to try. I would agree with making it thicker around the area that you place the powerhammer, if it cracks a few years down the line it would be devastating. And 4" would support the weight just fine, but it might not handle the vibration of the hammer pounding.
Reply:4" no 6" and seprate that slab from the rest of the floorChuckASME Pressure Vessel welder
Reply:HeyCheif, I agree w/ a lot that as been said. I have poured a lot of mud. I would suggest using the fiber as secondary reinforcement steel (rebar and mesh) as primary. Plan it out and beef up the slab. You are only going to pour it once. I would pour it 6" on good compacted soil. I woud also pour it as dry as I could but keep wetting it down as it cures.Take every step to insure your satisfaction. Most builders will tell you there is two kinds concrete: cracked and gonna crack. Good luck budJody
Reply:Well, I know what I would do in this case. I would thicken the slab at the area for the hammer. I'd blow out the area by a couple of feet in all directions. I would not use fiber as a primary reinforcement since that is not what it was ever designed to do regardless of how anyone else uses it. It is a secondary only...just ask the people who make the stuff. My preference is rebar with mesh tied to it as a secondary. You can isolate that slab area making it a floating slab, but without a proper design and prep, that can cause more troubles. I see guys get into trouble like that all the time. If you are planning on using plywood or mats, that should isolate it well enough so you would not actually need to isolate it. Bolting the machine down will transfer the vibrations just as well as if it were sitting on the concrete. If you have to bolt it, use isolation mounts. I won't comment on substrate prep since no slab desing was given. It will all vary to as to location anyway. The vast majority of my slabs would not need compaction since they are designed as stand alone or soil supported grid stiffened structures. The concrete WILL crack. Do not think it won't. You should think about cutting control joints each way in the slab to make it crack where you want it to....esp since you will have the hammer doing its thing on it. Take this all as you will. I wear many hats...one of the bigger ones just happens to be that of a concrete contractor.
Reply:the heaver you make the slab the better the hammer will workChuckASME Pressure Vessel welder
Reply:I use 5000psi concrete for all my general purpose pours. It resists the extremely hard water we have here MUCH better. I can attest to this first hand. The fiber reinforced stuff I used when I needed less than my local concrete supplier would deliver has done a great job and did not crack at all. But I did leave nice expansion joints because our summers get in excess of 115 degrees and swing down to the low 40s in the winter SOMETIMES.My pool contractor played HELL when he had to pull apart my 10X14 slab that he cracked with his dump truck. Of course, I poured it about 8 inches thick with rebar in it with about 4 inch OC spacing. I think you are getting good advice with the idea of reinforcing and thickening the slab where your tool will be installed. Best of both worlds!Lincoln Power Mig 210MP MIGLincoln Power Mig 350MP - MIG and Push-PullLincoln TIG 300-300Lincoln Hobby-Weld 110v  Thanks JLAMESCK TIG TORCH, gas diffuser, pyrex cupThermal Dynamics Cutmaster 101My brain
Reply:More good info, but the one I really like and the one I should have mentioned myself was  isolating and making it an independant slab.  Thus if it only needs to be a 10x10' section your fine with normal expansion paper not not just wet cutting unless you go all the way thru. I looked at my engineering specs for the AT&T  site work specs. And 6.5 bag is supposed to be 3500 psi which is supposed to be the minimal rating for garage flloors,sidewalks,basement floors ( not caps) and so on for the  normal flat work. These pads are designed for back up generators to make sure NO ones telephones go out, otherwise they loose money.  SO in any case one big critical note is we always ask for the mixer to bring cylinders since the tester wil be on site. This keeps him honest, or let them know that the tester will need a sample. AT&T always does but on other jobs we fudge it to keepem honest.  And in AT&T's jobs we have seen as high as 4700 PSI before and have failed once in 11 years around 2200 PSI A core sample was taken to be sure and it too failed but not nearly that bad to the 3500 requirement.   I like the " its own pad idea" ... weight of machine will determine thickness and surface impact determines PSI.  Machine shops usually use 8-9 bag.500 AMP AIRCO TIG LINCOLN PT185 100% DC @ 128 AMP-WTFSPEED GLASS 9002X MILLER THUNDERBOLT 225HOBBIEST TURNED WELDING JUNKIE8 2ND FIRECAT - SNOWMOBILE RACE CHASSIS FABRICATORPRIDE IS WHAT MAKES YOUR WORK SO GOOD
Reply:Originally Posted by DDA52Well, I know what I would do in this case. I would thicken the slab at the area for the hammer. I'd blow out the area by a couple of feet in all directions. I would not use fiber as a primary reinforcement since that is not what it was ever designed to do regardless of how anyone else uses it. It is a secondary only...just ask the people who make the stuff. My preference is rebar with mesh tied to it as a secondary. You can isolate that slab area making it a floating slab, but without a proper design and prep, that can cause more troubles. I see guys get into trouble like that all the time. If you are planning on using plywood or mats, that should isolate it well enough so you would not actually need to isolate it. Bolting the machine down will transfer the vibrations just as well as if it were sitting on the concrete. If you have to bolt it, use isolation mounts. I won't comment on substrate prep since no slab desing was given. It will all vary to as to location anyway. The vast majority of my slabs would not need compaction since they are designed as stand alone or soil supported grid stiffened structures. The concrete WILL crack. Do not think it won't. You should think about cutting control joints each way in the slab to make it crack where you want it to....esp since you will have the hammer doing its thing on it. Take this all as you will. I wear many hats...one of the bigger ones just happens to be that of a concrete contractor.
Reply:Another builders opinion.The fiberglass is not enough for a shop slab.  Wire will do  a better job preventing cracks.Rebar would be my choice under the hammer.  1/2" rebar going each direction 1 foot on center, go quite a bit larger than the footprint of the hammer.  I would definitely thicken it up where the hammer will be.
Reply:I'm with t red on the rebar also go a foot thick on the concrete and watch your slump! soupy mud will lose its strength keep it tight,your compaction of the ground is also very important ,been doing concrete 30 years  good luck !!!Victor SuperRanger O/A                                         Solar migLincoln Powermig 140Southbend 9in lathe350# kohlswa anvilMiller Maxstar 150 stl etc....