New concrete cracks in the Capital District for three reasons. It shrinks as it cures, the ground under it moves when it freezes, and it was poured without enough joints to control where that movement shows up. A slab with a compacted base, the right joint spacing and a proper cure will still crack, but only along the lines the crew cut for it.
Shrinkage cracks
Concrete loses water as it hardens and gets slightly smaller. A 20 foot slab shrinks about an eighth of an inch. If there is no joint to absorb that, the slab makes its own. We cut control joints every 8 to 10 feet, a quarter of the slab depth, within 12 hours of the pour. On a hot August day in Schenectady or Troy we cut the same evening.
Frost heave
Clay soil across the Capital District holds water. When it freezes it expands and lifts whatever sits on it. The fix is a base that drains. We strip organic soil, place 4 to 6 inches of crusher run, compact it in lifts and pitch the slab so surface water runs off instead of soaking in at the edge.
Random cracks you should not see
Diagonal cracks off an inside corner, a crack that follows a buried pipe, or a slab that is settling at one edge point to a base problem, not a concrete problem. Those are the ones we design out before the pour by compacting around utilities and thickening the slab at re-entrant corners.
What you can do after the pour
- Keep vehicles off for 7 days.
- No rock salt the first winter. Use sand or calcium chloride.
- Seal the slab after it cures and reseal every 2 to 3 years.
- Keep downspouts and sump discharge away from the slab edge.
Edges Unlimited pours driveways, sidewalks, garage floors and pads across Schenectady, Troy, Clifton Park and the Capital District. Request a free quote and we will walk the site with you.
