Pouring A Thick Concrete Pad.....

[Utopia Texas]

I am putting the figures together to install a 27KW generator for our house. We live on water and though the creek has never fLowed over the bank I would like to have the top of the slab\pad 1 foot above ground level. Can I fill the center of the form with crushed cinder blocks to fill in before pouring the concrete or should the whole pad be 1 foot deep? The unit will weight in at 960 pounds. Am I being too cheap filling space with crushed material?

 

[crazyal]

What are the length and width of the pad? Are you planning on using rebar? The only issue I can see with using broken up blocks is that you could end up with voids because the cement didn't fully get down between them. Also if you are going to be standing in the form while pouring cement they will be difficult to walk on. The last thing you'll want to do is trip and fall into wet cement. You don't want to have the the cement watered down so it'll flow better either, as it will weaken it. If the pad isn't too big then you're most likely not talking much of a savings (that's why I asked). Not sure if this is something you are going to just buy bags of cement and mix yourself or having a mixer come in and pour it. If you're doing it yourself and you have plenty of help you could have someone putting the broken up blocks into the slab after you pour it.

 

[dusty3030]

I wouldn't pour a 1 foot thick pad period.


If a nat gas where the base of the unit is basically steel skids dig a hole for each corner, set 4 piers and if put it 2 feet off the ground with anchor bolts set in top of each pier and bolt it down to those - 1 each corner.

 

[Diamondpilot]

My hanger floor is 10" thick with rebarb and fiber. Not a single crack. We cut the floor open 24" wide 40' long to add a full bath. The cement was fully cured.

Chris

 

[Egon]

Should not be any problem if you keep the minimum depth of slab at four plus inches. Will you have bolt downs?

 

[Utopia Texas]

I wouldn't pour a 1 foot thick pad period.


If a nat gas where the base of the unit is basically steel skids dig a hole for each corner, set 4 piers and if put it 2 feet off the ground with anchor bolts set in top of each pier and bolt it down to those - 1 each corner.

Yes, This type unit is on a steal frame with a enclosed box type cover so just corner posts might work well. Or a "Rectangle Picture Frame" of concrete. With the center empty the electric lines to the house and propane line could be run easily and then the center section filled with gravel. This will be near the house so "The Boss" has to approve how it looks! I need to figure out cubic feet of concrete necessary for different set ups and call locally to see what minimum amounts can be delivered. This is by no means a huge pad....a little over 5 feet long and 3 feet wide and one foot tall.

 

[Utopia Texas]

Should not be any problem if you keep the minimum depth of slab at four plus inches. Will you have bolt downs?

Yes, I plan on bolts in the concrete through the lower frame just in case of vibration. Wouldn't want a thousand pound walking its way off its mount! This will probably be over kill. My brother already has a similar unit and it runs really smooth.

 

[Gary Fowler]

My hanger floor is 10" thick with rebarb and fiber. Not a single crack. We cut the floor open 24" wide 40' long to add a full bath. The cement was fully cured.

Chris

There is no issue with concrete thickness and curing. I have done inspections on slabs that are over 8 feet thick and they all cure in 28 days just like a 4" slab. Concrete will cure even when placed underwater. NOTE : studies have shown that concrete continues to cure and get harder for around 100 years but we only expect it to reach its design strength in 28 days regardless of thickness.
I have seen raised slabs poured when the perimeter is put in like a 6-8" thick wall (thickness depends on the height of the raised slab) and then it is backfilled with either sand or soil and compacted in maximum of 6" lifts using vibratory compactors of various sizes depending on the size of the slab. Small areas use whacker packer or vibra-plate and larger ones might use the large 15ton roller with vibrating drum.

For the OP slab I am assuming he will only make it 6-12" wider than the machine he is setting on it so he might just pack with a hand plate packer. What ever he uses needs to be solidly packed in so it doesn't settle.

Unless he is batch mixing it himself, a redi-mix company is going to charge him for minimum of 4 yards so he may as well set up for that amount and make his slab as big and as high so as to useup the minimum charge for the concrete. He can make one heck of a slab for a generator with 4 years of concrete.

 

[Egon]

Yes, I plan on bolts in the concrete through the lower frame just in case of vibration. Wouldn't want a thousand pound walking its way off its mount! This will probably be over kill. My brother already has a similar unit and it runs really smooth.

Sounds like you have it all played out. Now the SWMBO on looks factor is left.

 

[crazyal]

A 3x5x1 would be 15 cubic feet, less than a yard. That would be 25 80lbs bags. I'm lucky as I can get small loads, even as small as 1 yard. Anything less they might say no. I would just run the conduit through the slab for gas and power and then just pour around it. I would also look into cement coloring additive. Since you're going to have it up by a foot and you need to please the foreman showing her some optional colors to choose from will help get her approval. My garage is sitting on what's called an "Alaskan slab" It's 24" thick around the outside edges and about 6" in the center. You could do something like this but the savings would be pretty much nothing.