It looks like a lawn but it performs with the structural capacity of a well-designed concrete slab on grade. The system is essentially a cast-in-place, continuously reinforced slab on grade with regularly spaced holes going through the full slab thickness. In most cases the holes are filled with soil and planted with grass.
Work begins with preparation of a subgrade designed for local drainage conditions, leveled to 5 1/2 inches below the desired finish grade. Reinforcing steel, either bars or welded wire fabric, is supported on bar chairs 2 to 3 inches above the subgrade. The forms are coated with form oil, then placed directly on the subgrade. The 4000-psi concrete mix is placed at high slump achieved with a superplasticizer. Maximum aggregate size is specified as 3/8 inch. Workers use brooms to level the concrete flush with the top of the forms, leaving a broomed surface finish. As soon as the concrete is stiff enough to support itself, the crew may begin to remove the forms using a pulling tool. Traffic over the slab is restricted for 7 days following concreting. After curing is complete, the holes are usually filled with topsoil and seeded to grass.