How To Remove Concrete
Concrete is great stuff, and it deserves its title as King of Building Materials, but some homebuilders (and remodelers) can use it to excess. If you’d like to look out your back door and see wildflowers and herbs instead of a sweltering gray slab, you’ll be glad to know that while this is a back-breaking job, it’s not skilled work.
What’s in a slab?
A typical outdoor concrete slab ranges in thickness from 3 to 6 inches. Patios and stoops usually are on the thinner side, while driveways tend to be at the thicker end of the range. A slab may or may not contain reinforcing metal inside, in the form or wire mesh and/or rebar. There’s no way of knowing what’s in there until you start breaking up the concrete, so you might get lucky and have no steel in your slab (even the country’s most famous house, Fallingwater, was originally built with a lot less steel than the plans called for). Below the slab is a subbase of compacted gravel. This might be a few inches thick or a lot thicker, depending on the site conditions. After you break up and remove the concrete, you’ll have to dig out all the gravel, too, to make room for plant-nourishing soil.
How concrete breaks
Concrete is strong, but it’s also brittle. You can hammer all day at the center of a slab — where the concrete is evenly supported — with no appreciable effect. But if you hammer at the edge of the slab, where the ground underneath can shift or be displaced a little, the concrete will break. This is because you’re essentially bending the concrete, which is its main weakness. If you want to break up a large piece of concrete for removal, pry up one end and set it down on some rubble or a scrap of timber, then strike the piece in the center.