How to fix cracks in concrete floors

Concrete floors that are badly cracked may be repaired by topping the existing floor with a 2-inch layer of 1:2:4 mix concrete. This should be reinforced by lightweight steel-wire mesh, not lighter than No. 14 gauge, placed in the middle of the new layer.  To prevent cracking, the floor should be kept moist for a period of not less than 3 days.

Immediately before new concrete is poured, dry floors should be roughened, cleaned, and wetted and cement-sand grout (1 part cement to 2 parts sand by volume) scrubbed in to form a bond. If the old floor has been penetrated by seepage, either a bituminous coating or membrane waterproofing treatment should be applied to the surface of the old floor before the new concrete topping is placed.