Use a concrete saw to cut fresh concrete one-half the depth of the slab. Space cuts according to the formula: the thickness of the slab in inches multiplied by three. For instance, a 4-inch slab ...

"If the jobsite requires 4,000 psi concrete and the contractor places it by hand, the best strength the concrete may reach is 3,000 psi; that's because it's not vibrated," Lindley says.