Concrete call-backs are more frequent in the residential market. What is surprising is that the same mistakes recur season after season, job after job. Careful planning and good workmanship can eliminate these mistakes and cut the number of call-backs.
On commercial pours, inspectors enforce the 90-minute discharge rule of ASTM C 94, Specification for Readymixed Concrete. This is not true in the world of residential concrete.
RAPID SURFACE DRYING
When the slab surface dries rapidly and starts to crust, finishers on residential jobs may rewet and then trowel the concrete surface. This weakens the surface and may cause scaling or poor wear resistance. By following the guidelines in ACI 305, Hot Weather Concreting, contractors can avoid prematurely drying surfaces.
LACK OF COLD WEATHER CURING
Many finishers think curing is needed only in very hot weather. They fail to keep the concrete moist after placement during cold weather. But curing is the final safeguard against surface deterioration.
Jointing errors cause many cracking problems. Common residential jointing errors include: joints too far apart; joints not cut deeply enough; and unjointed reentrant corners.