Look for "safe when used as directed." Calcium chloride generates heat (exothermic reaction) which melts ice faster than rock salt but can be harsh on new concrete (less than one year old).
Flatter shapes provide more surface area contact for thinner layers of ice or snow. where to buy calcium chloride ice melt
Used primarily for pre-treating surfaces before a storm to prevent ice from bonding to the pavement. Look for "safe when used as directed