Step 1 Prepare the Concrete
Rough up the surface of the concrete and remove any sealer or curing compound with a bead blaster. Slowly push the blaster across the floor as it shoots metal balls at the floor and vacuums them up. The impact will wear off any coatings and create a rough surface for the mortar. Snap chalk lines at the middle of opposite sides. Measure 3 feet from the intersection along one line and 4 feet along the other line. If the distance between the points is 5 feet, the lines are square. If not, reposition one of the lines until it is square with the other.