A small concrete slab doesn’t cost much to DIY ... using a trowel or flat shovel, to fill voids. If the form appears to be full and the surface is even, use a hammer to gently tap the form ...

ASTM E1745-11: Standard Specification for Plastic Water Vapor Retarders used in Contact with Soil or Granular Fill under Concrete Slabs ASTM E1643-11: Standard Practice for Selection, Design ...

When positioned in the upper or top portion of the slab thickness, steel reinforcement limits the widths of random cracks that may occur because of concrete shrinkage and temperature restraints ...