Deicing salt
Chemicals applied to melt ice on concrete surfaces. They dramatically accelerate surface scaling and drive chlorides toward embedded steel.
What does deicing salt mean?
Salt worsens freeze-thaw damage by increasing the number of freezing cycles and the degree of saturation at the surface, on top of introducing chlorides. Magnesium and calcium chloride products are more aggressive to concrete than sodium chloride, and ammonium-based fertilizers used as deicers attack concrete chemically. New concrete is especially vulnerable and is generally kept salt-free through its first winter.
In practice
Telling a homeowner not to salt a new driveway for the first winter is the single cheapest durability advice a contractor can give.