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Concrete Floor Problems

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renoman

Structural
May 19, 2003
1
I have a two-story workshop/garage(26'X 26')and 2x6 construction. The building is built on a concrete slab approx. 4-6" thick). The walls are sitting on a cinder block curb(8" high). The property has been regraded due to a septic tank being installed and now the floor sits well below grade. Is it possible to pour concrete on top of the existing floor? Grade needs to come up 8"(a lot of concrete). Should I use crushed limestone to reduce cost and weight? Should the cinder block be removed/replaced with concrete or use them as a form? I'm in central Canada/very cold winters. Close to a lake and have a high water table.
 
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Firstly, you can use a lightweight aggregate such as recycled polystyrene (BST) in your concrete topping which will produce adequate compressive strength with lower load bearing.

Secondly, consider using an epoxy resin as a bonding agent for the new topping to the existing slab. Clean the existing slab, apply the epoxy, and while the epoxy is still tacky pour the topping over it. This should yeild a bond strength between the existing concrete and the topping of at least 110% of the base slab strength.
 
Another option which would could still provide a slab without owering the load bearing is to create a waffle slab with 4" thick foam. You'd be surprised at the capacity you will get from 4" thick slabs with two-way action spanning to 8" thick ribs. Take advantage of the continuity also. You could also dowel into the block wall and pour a continuous rib around the perimeter.

As for the cold and the water table, you don't mention what the walls are founded on. Are there continuous footings at the walls which extend beyond the frost line?
 
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