I assured my DH that the members here could supply experienced information. He is about to start construction of our Power House. He needs to build a reinforced concrete floor. This will contain, our 550 gallon water tank (this will also have mounted above it our hydro generator). He needs this to be strong enough to support the weight. Any settling will throw off our pipes to the house etc. The building will be about 10 x 12. It will also house our battery bank. We have an artesian well so there will be no well pump just the water pipes flowing from the well to the generator into the water tank then to the house etc. I hope I have explained enough. He has used concrete for minor jobs before but nothing like a floor. He has searched the web for information and has not found anything. Thank you in advance for your help. Thrifty

-- Thrifty Sarrah (olefashion@hotmail.com), February 23, 2002

Answers

You might look at this site: Military Manual Concrete & Masonry, http://www.adtdl.army.mil/cgi-bin/atdl.dll/fm/5- 428/toc.htm

-- BC (desertdweller44@yahoo.com), February 23, 2002.

I would suggest fiber reinforced concrete all concrete companys use it, if you are going with them (Concrete Company)it might cost about $10.00 more per yard but you can forget the reinforcement wire and labor so there is still something to gain in that way.if you are going to mix and pour your own you may be able to buy the fiber off of them and mix it as your mixing. Some people frown on fibered because you will not get as slick a finished look but anywhere there is going to be moisture it is prefered to have a bit rougher finish as moisture on a cement floor can be slippery when wet as for the strength fibered reinforced concrete is 6 times stronger than using reinforcement wire.

-- ned (homeontherange@hotmail.com), February 23, 2002.

I have poured a lot of concrete and proabily can help you but I need to know what type soil do you have? What kind of primeter wall are planed, wood or blocks? Is the ground level? Is it earth or gravel or solid stone? What is the total weight the slab will suppert? Will the equipment have its own vibration damptner? A monolithic slab sounds right at the moment; thats a slab and footer poured at the same time. Give us details of what you have.

-- mitch hearn (moopups@citlink.net), February 23, 2002.

You need to know what the frost depth is in your area. After that you excavate a perimeter footing as well as the area inside the perimeter.

The bottom of the footing will have to be below the frost depth. The building code in your area should have that info. Build your forms around the outside so that the top of forms are high enough to give you the thickness of the slab you want. Six inches should be good.

I'd put four #4 rebar spaced out evenly in the footing and held off the ground by bricks. The rebar should be tied to each other and form a continuous bar all the way around. I'd think about some way of accessing the pipes in the future. If they're embedded in concrete, you have a problem if you need to replace them. It might be worth your while to have an underground trench formed into the slab so that the pipes pass below the floor surface through the outside and then into the ground below frost depth.

For the area inside of the footings you only have to dig out enough to get down to solid ground and allow for the concrete and gravel. I'd lay in a sheet of plastic under the floor area and then put down a few inches of gravel.

If you put in mesh, remember to use a hook to pull it off the bottom as you place the concrete.

Make sure the footings are well braced, level and square. When you place the concrete you'll do the footings and the floor in one pour. Insert some anchors for the walls, before the concrete sets up.

If you're pouring concrete when the temperature goes below freezing you need to protect the concrete. If you have a source of flowing water, directing that onto the concrete after it sets up using a soaker hose under a tarp covering the slab will keep the concrete from freezing.

-- Darren (df1@infi.net), February 23, 2002.

I also would suggest when preparing for your slab to make positivly sure you have no loose fill before pouring the cement if a filler is needed use peagravel there will be no settling but if sand is used you will need to water it in really good to settle it first and then if your ground holds moisture it could cause you added problems.Good luck with your project.

-- Ned (homeontherange@hotmail.com), February 23, 2002.

If the finish of your floor does not have to be perfect you can lay iight plastic and straw to cover it to protect it from freezing,or if buying from concrete company have them add 1-2% calcium to the mix to protect it from freezing.

-- Ned (homeontherange@hotmail.com), February 23, 2002.

Murphy's Law. Try to ensure that when the water escapes (and it will) it can't flow or spray onto the batteries - I would strongly advise separate rooms.

-- Don Armstrong (darmst@yahoo.com.au), February 23, 2002.

Yeah sure. Add calcium and watch it crack in a few years. If the ground has been properly rolled, not tamped, laying 'crete is no big deal. With a 12-in base of gravel (washed or otherwise), depending on your frost line, lay eight inches of 'crete in forms. 4000-6000 psi with 6-in of slump. Use either #4 re-bar, 6x6 wire mesh or fiberglass mesh for re-inforcement. Wetting for 28-days cures it correctly. If you can wet it longer than 28-days do it. It increases the hardness and reduces the cracks. Keeping everything off the pour is most important. Don't even walk on it. Calcium is not necessary. Don't pour below 32-deg.

-- al (yr2012@hotmail.com), February 23, 2002.

Darren and Al:

Reading the two of your posts...You don't mean to keep water flowing over it for 28 days in order for it to cure properly, do you?????

-- Audie (paxtours@alaska.net), February 23, 2002.

Audie when they take concrete test cylinders to determine what strength the concrete should develop, they place them in a tank of water to cure after the intial setup. After 28 days they take them out and crush the cylinder in a machine to get the compressive strength.

Keeping concrete wet for the 28 days or longer is the best way to get the highest strength out of the mix the concrete plant delivers. There are curing compounds you can spray on concrete to do the same thing. For a small job the cost probably isn't worth it.

You don't need a river flowing over the concrete. If you can use burlap and constantly keep it wet, you'll get the same result. The key is to not let the surface of the concrete dry out. If it's allowed to dry prematurely you have a greater chance of cracking, surface spalling and dusting.

-- Darren (df1@infi.net), February 23, 2002.

This maybe more than what we thought it would be. However, there are a lot of idea's you all have given him to working with. This project is not suppose to cost mega bucks. We have a solid clay base. The frost is negligable here. Hits the freeze mark for a few days a season only. The link to the Masonary site was restricted to Army personnel only so we weren't able to access that. DH thinks he has a solution for any shifting by using flexable piping. That was a good idea, I think. I suggested from the beginning that perhaps we should just build on the OG clay base and call it good enuff... If this is going to be expensive he may rethink my original suggestion. The battery bank will be built up on a wooden raised table or platform. The idea was to control the battery temperature by being in close proximity to the water tank, while protecting the batteries from water. He will reread and recalculate the costs and see how we proceed. Thanks you all very much.

-- Thrifty Sarrah (olefashion@hotmail.com), February 23, 2002.

I’ll recheck on the manual link, you might look at this one on Concrete Slabs, http://www.oldhouseweb.net/stories/Detailed/706.shtml, it has pictures that show what some of the posts are referring to, as to footers, vapor barriers and gravel fill, etc., I think.

-- BC (desertdweller44@yahoo.com), February 23, 2002.

I worked for a concrete company for 25 years,but don't claim to know everything about concrete.There are a few basics you need to look out for,use rebar under your slab no matter how good the base seems,also fibermesh is the way to go instead of reenforcement wire.And the big thing is to remember if you hire a finisher he will be looking to make his job easier not pour you a long lasting slab.Too much water ruins concrete,if your finisher wants more than a 5" slump then get super plasticer,that you add on the job,most none commerical concrete is placed incorrectly,but it can be done right and if done right it will last a lifetime.

-- Gary (burnett_gary@msn.com), February 23, 2002.

If Money is a major factor why not use railroad ties to build a retainig wall (sandbox)2 feet tall overlap the joints nail with twelve inch spikes use two pound shop hammer, dig a foot down and atrench to take pipes out, fill it with sand. If you do spring a leak the sand ought to absorb the water. Railroad ties sand etc. ought to be under $ 200. I layed a 4 inch slab 16inch by 4inch footing for a 16 ft by 16ft slab and it cost me 600 dollars that was with 2500lb test. You might also just pour a stem wall 6 inch wide 1 foot deep and 2 foot out of the grond fill with sand use four runs of rebar. fill with sand and hope it might work.

-- Monty D. Montgomery (montmont@nts-online.net), February 24, 2002.

Visit this site

http://webx.taunton.com/WebX?14@238.27bsamISbpu^0@.ee6b303

It is the discussion forum from The Taunton Press "Fine Homebuilding" Magazine.

Their search function will lead you to discussions for garage floors, slab on grade etc.

-- Deborah Hardy (virgil@igs.net), February 24, 2002.

Can someone describe the term "slump" that is used in reference to concrete?

-- John Fritz (JohnFritz24@hotmail.com), February 27, 2002.

Slump is when you take a cilinder twelve inches tall fill it with concret imediatly remove it the cilinder then measure the movement of the concrete if it moves down two inches its a two inch slump if it moves down ten inches its a ten. What it boils down to is how wet the mud is. I tried to make the definition as simpile as it was made to me twenty years ago.

-- Monty D.Montgomery (montmont@nts-online.net), February 28, 2002.