If left exposed to the air, it hardens quickly.

Eastern dirt hardens quickly in the sun, and it is often used as a building material by poorer inhabitants.

The stucco will harden quickly; avoid mixing more than you can apply in an hour.

The plug quickly hardens, and leaves a small raised area on the seed surface.

A look of sorrow came briefly to his eyes, then quickly hardened into determination.

Because the residue hardened quickly, it was considered ideal landfill for building foundations.

The mixture quickly hardens and he gets stuck in it.

Once exposed it hardens quickly and will last for hundreds of years.

The foam quickly hardened creating a mound that built up along the base of the gun system.

The shaft had been filled with concrete which hardened quickly.