I intend to pour a slab where my deck steps will land. The dimensions are
approximately 80"x24"x6" (LxWxD) or roughly 6-2/3 cubic feet. The ready-mix
plants in town won't take an order for anything less then 2 cubic yards, so
I'm left to mix Quikcrete in my wheelbarrow. I'm thinking mixing 20 40#
bags of Quikrete is going to be a huge chore, so I'm wondering if I can
break up an existing concrete slab (the wife decided she wanted the steps
somewhere else) and use that as filler material -- not to save money but
rather to cut down on the amount of mixing I will have to do. Is this a
stupid thing to do? Would it considerably weaken the slab? If not, what
would your filler-to-mix ratio be? Thanks for any advice.

Dale