Remove as much snow from the top of the ice as possible, using a push broom or plastic snow shovel. The less snow on top of the ice, the more effective any de-icing compound will be.
Sprinkle a de-icing compound that contains only calcium chloride as an active agent evenly across the icy deck surface. Spread the compound thinly first, then return after two or three hours to sprinkle more where the ice is still present or thick.
Clean white residue left by the calcium chloride de-icer as desired or in the spring. The AZEK decking can be cleaned with ordinary household products or non-abrasive cleaners that are plastic friendly.