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Posted: 1/12/2002 6:02:36 AM EDT
I have to pour a floor in my garage. I think about 4 inches will do it. It already has a cement floor but in poor condition. I will be using 2x6's to frame it. The size is 30' x 30'. I will be placing some heavy machinery in there. Do I need to reinforce the floor? I'm thinking that I will call for a delivery. Does it matter about the weather, i.e., how cold and damp it is? Any other things to consider? Thanks. bybon
Link Posted: 1/12/2002 6:28:33 AM EDT
[Last Edit: 1/12/2002 6:31:51 AM EDT by Rich314]
YES the floor needs steel. Up to you but I would imagine there are city codes you must follow, I wouldnt and just over build. 1/2" should do well if you use enough. a 12" grid of 1/2 sounds minimum. If you like cracked garage floors then by all means use mesh. As for weather, depends on how cold your talking aboot. Concrete that cures slower, cures harder. A very hot day will suck the water out too fast. That`s why we put sprinklers on fresh slabs for a day or two. It can get too cold for a pour but I dont know what that is. Get the cement delivered and have at least 2 guys that know how to finish concrete on hand.
Link Posted: 1/12/2002 6:37:28 AM EDT
Make sure you use rebar and put your break each eight feet or it will crack.In cold weather to keep the concrete from frost I use hay or plastic to cover the slab.I've used pressure treated wood for the break and you can also by the black material stuff at any mason supply place.good luck
Link Posted: 1/12/2002 6:47:26 AM EDT
Garage floor needs at least 5 inches,6 would be better.I would also suggest the fiberglass fiber.Find out what bag mix is code in your aera.Ok I see ypo already have a floor.Does it have any major uneven cracks?If it does the floor has shifted or still is.If its still moving the new layer wont stop it.The fiber would really work good here.I dont think you need any rebar if the other floor is solid.
Link Posted: 1/12/2002 3:36:22 PM EDT
Since this is a garage floor, it probably won't be subjected to the elements. This means you shouldn't need to worry about sealing the construction joints or cracks against moisture. You shouldn't need reinforcement if the subgrade can be compacted to proper density. However, sufficient compaction of the subgrade may not be possible since it is inside a structure. The machinery involved would probably not fit inside your garage. If the subgrade is not dense enough, it cannot support the concrete sufficiently against flexure loading. Since concrete is quite weak in tension, any flexing of the concrete can cause cracks. This is where steel reinforcement helps out since it can take those tensile loads. Tied steel reinforcement is most likely overkill, heavy gauge steel mesh should work well enough. You will want the mesh to be placed closer to the bottom of the slab since this is where the tensile stresses will be greatest under flexure loading. There are different gauge sizes of steel mesh, talk to the concrete plant guy on what he thinks would be best. If you are willing to spend some money, you probably want at least six inches of concrete, any more would probably be overkill. Call up your concrete plant and see what types of concrete they have to offer. Ask about what type of concrete they use for highway construction, that should work well enough. Most likely they are talking about a 6 sack mix which means they use 6 sacks of cement for every cubic yard of concrete. A 7 sack mix would be even stronger and is normally used for bridge decks and concrete used in structures. Anything over a 7 sack mix would probably be overkill. You want concrete spec'd for a strength of 3500 to 4000 psi. Finally, proper placement of the concrete is crucial for proper strength. Sometimes the guys placing the concrete are idiots and don't know what they are doing. Make sure you check around and get someone that knows what they are doing. Contraction or construction joints should be placed roughly every 10 to 12 feet. Depending on what the dimensions of the garage are, one joint down the center may be sufficient. One or two transverse joints would probably work too. Make sure they have some way to vibrate the concrete when it is being placed. This will consolidate the concrete and remove any voids due to placement procedures.
Link Posted: 1/12/2002 3:38:10 PM EDT
Concrete doesn't just magically gain all its strength overnight, it can take up to 28 days for it to cure to full strength. However, for concrete to continue to gain strenght, it must be kept wet. There are a few ways to go about doing this. The easiest is to have them spray on some curing compound after placement. This will seal the surface and not let the water evaporate out of the concrete, thereby allowing it to continue to react with the cement. You could also use wet burlap, just make sure it doesn't dry out. You should only need to keep the concrete wet for about 7 days max, and 3 would probably work out good enough. Try to keep heavy machinery and vehicles off of it for at least 14 days. Most likely, if you get your concrete from a plant that batches out concrete for major construction projects, the people working there will be of help. There is a chance they could be an idiot, though, so be careful. I have learned this the hard way. Anyway, let them know what you are planning to do, and ask for suggestions. If you know someone that is a civil engineer or does this type of work for a living, talk to them and get suggestions. Hope this helps, there is a lot more that I could go into, but this should at least get to going down the right path.
Link Posted: 1/12/2002 4:29:21 PM EDT
Link Posted: 1/12/2002 4:37:33 PM EDT
Rip out the old slab, the subgrade should be pretty good, so don't dig it up unless you have to. Build your forms, make sure elevations are good, 4 or 6 inches from top of form. If you do a 4 inch slab, you my want to thicken the edges. (turn down) Get yourself some #5 or 6 rebar, tie it on 3 ft centers. Go down to the newest housing development, look for the guys who are actually pouring the slabs, the guys who actually have concrete on them, not the guy standing around or sitting in PU, barking orders. Pick the smartest looking one, take him to your project, ask him how much. (Before this step call a concrete contractor and get an estimate, so you will have an idea of what it would cost). Concrete is ordered in yards (27 cubic ft to a yard). 1 yard will do approx 81sq ft 4 inches thick, so go figure, literally. Or just give the dimensions to the batch plant, they will tell you what you need, including PSI. All concrete cracks, joints limit the amount of cracking. Your subgrade has been under a slab, I assume for awhile, so don't sweat the subgrade. When they pour the slab, you want to make sure the rebar gets pulled up into the middle of the slab If this is a shop (auto etc.) have a broom finish put on it, you don't want a glass smooth slab, you will be falling on your a** everytime it gets wet or oily. The guys doing the slab will do whatever the weather dictates, so don't sweat that either. And if I sound like I am full of BS, go down to Home Depot/Lowes and buy a book. waterdog
Link Posted: 1/12/2002 8:48:46 PM EDT
Gentlemen, Thanks much for all of your imput. I certainly have a better grasp of what needs to be done. I especially appreciate the words of experience. I will be converting this garage into a machine shop. I will have CNC milling machines, a lathe, surface grinder, saws, air compressor and the like. Since I own a machine shop in another town presently, my aim is to get closer to home and family. Again, thanks much.
Link Posted: 1/12/2002 10:16:49 PM EDT
bybon, I believe I saw on a episode of This Old House a concrete that had fiberglass strands mixed in with the concrete, it was supposed to make the concrete quite a bit stronger than normal concrete. I would get references and check out the guys work. Also I would check with the city/town and see what paperwork is necessary for your job. The contractor should have workers insurance for his men so you don't get sued if one of them gets hurt on your property, and pay for the concete and material yourself, that way you know it's all paid for. These guys are in and out of business everyday, so watch who you get.
Link Posted: 1/12/2002 10:37:22 PM EDT
Soooo what did she do ??? mixing concrete and filling a hole???mmm no one will ever find out if you do it yourself[;)]
Link Posted: 1/13/2002 2:19:40 AM EDT
BTW, the fiberglass strands mix has also been referred to as "cat hairs." Works great...just did a driveway with 3500 psi...no metal. As far as the brush finish, yea, you won't slip on it...but it is hell to sweep up. Just don't spill stuff. Oh, and if the truck can't easily reach the pad, consider ordering a pumper. Just did a 3 level deck with one of these....love it. Anarki
Link Posted: 1/13/2002 7:35:20 AM EDT
I installed the utility piping at the Pepsi Plant just north of Indianapolis about 15 years ago. When I first went there for a job walk they were pouring the slab. The concrete contractor wasn't using "doabies" (small concrete blocks with wire to keep the rebar up)and his men were just pulling up the rebar with their claw hammers. After the proper time Pepsi started using their wherehouse for storage. When the first truck entered we all heard large cracking sounds. Their whole slab cracked everywhere. this place was huge.It could have been measured in acres (lots of acres). An investigation found that this was due to the rebar setteling. Their fix was to have 6 guys inject epoxy through pre-drilled holes that had plastic hose nossels glued to them. This took every bit of six months. My garage is 1,200 sqft, needless to say when it was poured I was a picky SOB. One thing that I designed into my slab was 8" of slope on 30'. I did this because I can't remember all the times that I got wet because the slab I was working on had ponds of water on them. I also wanted to be able to wash my rides in the garage. This slope has worked fine for me. Andy
Link Posted: 1/13/2002 8:22:02 AM EDT
Although I'm not an expert at concrete, I have used the fiber stuff and it comes highly recommended. It IS expensive, but worth it. If you are using the machinery you say, then go with the fiber. Our machinery weighed in at 100,000 lbs+, and operating at hydrolic pressures of around 1200 tons+/-. We really hammered the floors. I have seen the machinery cause sink holes that would cause about 60 gallons of water to ebb and flow into the cracks in the floor everytime the machine opened and closed which was once every 20-30 seconds. It would take about 4-5 seconds for that much water to disappear when the machine closed, then reappear when it opened. We would have to jackhammer the floor out and replace it with the fiber stuff. But then again, the machinery you are using isn't the type that would put that kind of stress on the floor.
Link Posted: 1/13/2002 11:15:06 AM EDT
One piece of advice - Get the first truck of the day. If you pour later in the AM or in the PM, drivers usually "recycle" their left-over concrete and it's crap compared to fresh mix. Find out what time the plant sends their first truck out and plan accordingly.
Link Posted: 1/14/2002 12:09:04 PM EDT
I would make sure I used a good bonding agent and sray or brush it on the old slab.I would also talk to the concrete company about bag mix, and would suggest using expansion joint around the perimiter of the slab(this is a fiberlike board that can be cut to the thickness size of your slab). BUT DO NOT FORGET THE BONDING AGENT.I would tell the crete company what the surface will be used for and they will recomend what type of steel you should use. I would also say that the fiberglass additive make for one rough ass surface. I drove a concrete miexer for 8 years but it has been awhile so be sure and ask the advice of the salesman for the company. Good luck. I will also tell you that concrete is an engineered product,every gallon of water you add will affect the srenght of the floor when completed.
Link Posted: 1/14/2002 12:46:27 PM EDT
The depth and breadth of information available here on just about any topic never ceases to amaze me. You guys are the laser-guided smart bomb, yo. [;)]
Link Posted: 1/14/2002 12:49:53 PM EDT
Originally Posted By Jarhead_22: The depth and breadth of information available here on just about any topic never ceases to amaze me. You guys are the laser-guided smart bomb, yo. [;)]
View Quote
Here, here. Hey, I've got a rash on my.......does anyone know anything about it????? [BD]
Link Posted: 1/14/2002 1:18:49 PM EDT
Link Posted: 1/14/2002 4:33:46 PM EDT
I must agree with Jarhead_22. I bet I would not have found this scope of information from a single source. Thanks to all who so kindly gave of their time and knowledge. Just wait till I ask about powering the shop with a rotary phase converter. Again, thanks. bybon
Link Posted: 1/14/2002 6:20:24 PM EDT
[Last Edit: 1/15/2002 6:17:57 AM EDT by Tanstaafl]
E-mail me for a phone # and I'll talk some of the details with you. BTW I'm a concrete repair contractor. If existing slab is cracked but not sinking the subgrade should be adequate. Look at the loads you will be putting in the shop (foot, forklift, etc.) to determine the need for additional investigation of the subgrade. It is a lot easier and less expensive to check now than repair later. Failure to understand this basic concept keeps me in business. [:D] Check this link, lots of good info: [url]www.concretenetwork.com[/url] edited to add link
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