Ice melt should be applied before snow and ice is expected, or as soon as it arrives. You should also use ice melts after snow is cleared away.
Some ice melts are bad for concrete, especially if the concrete is cracked or was recently laid. However, ice melts like magnesium chloride and calcium chloride can be safe for concrete.
To clear an icy driveway quickly, first shovel any snow that's covering the ice. Then cover the driveway with rock salt, or magnesium chloride pellets, or calcium chloride pellets. Once the ice melts, shovel it away. If you're using rock salt, you can spray warm water to help the ice melt quicker.