Elevated concrete is often used on balconies and breezeways of multifamily construction projects. This concrete is the same formulation that is used on ground poured driveways and sidewalks around those same projects. Concrete used in sidewalks and in other on grade applications is not set over waterproof membranes like elevated concrete is. When it rains, rain soaks into this on-grade concrete and eventually percolates through or evaporates out.
Elevated concrete lays directly on a waterproof membrane. This waterproof membrane in these elevated applications traps moisture inside these elevated slabs. In warm climates, water trapped in concrete will leach unreacted salts out of the slab leading to white crust forming on the top of the slab called efflorescence. In cold climates, trapped water will expand when frozen causing cracks, spauling and other defects in the slab.
DM1 Is the solution to these elevated concrete headaches. DM1 is a drainage mat made from UV stable Polyolefin which makes it rigid enough to stand up to the weight of the slab sitting on top of it. After waterproofing is complete, the DM1 is installed dimple side up. Then, concrete is poured directly over the mat. There is a scrim on top of the mat that keeps the concrete from filling it. The result is a concrete slab sitting atop pillars of drainage mat. Water that enters the concrete can then permeate the slab and enter the drainage mat where it can flow out to the drip edge. A slab that can breathe from the top and bottom will not suffer the effects of efflorescence or cracking due to freeze thaw cycles.