Overpouring Old Concrete with New Concrete
Concrete that is damaged on the surface but is structurally sound can be repaired by resurfacing. Resurfacing is pouring a thin layer of sand-mix concrete over the existing concrete.
Photos below are courtesy of the Black and Decker Home Improvement Library’s "Home Masonry Repairs and Projects" by Creative Publishing International.
Side View of the completed job
Clean the surface thoroughly. If the surface is flaking or spalled, scrape it with a spade to dislodge as much loose concrete as possible, then sweep the surface clean.
Dig a 6" wide trench around the surface on all sides to create room for 2*4 forms.
Stake 2*4 forms flush against the sides of the concrete slabs, 1" to 2" above the concrete surface (make sure height is even). Drive stakes every 3 ft. and at every joint in the forms. Mark control joint locations onto the outside of the forms, directly above existing control joints. Coat the inside edges of the forms with vegetable oil (so the forms will strip off the newly poured concrete once it has hardened).
Apply a thin layer of bonding adhesive over the entire surface. Follow the directions on the bonding adhesive product carefully. Instructions for similar products may differ slightly.
Mix concrete using sand-mix concrete. Make the mixture slightly stiffer (drier) than normal concrete. Spread the concrete, then press down on the concrete with 2*4 or shovel to pack the mixture into the forms. Smooth the surface with a screed board.
Calculate how much material you will need with the concrete calculator.
Float the concrete with a wood float, then tool with an edger. Recreate any surface treatment, like brooming, used on the original surface. Cut control joints in the original locations. Let the surface cure for one week, covered with plastic.
This procedure is best used on walkways or other small areas.