As I researched about your question I found out that - Table Salt is faster, because it's much finer, therefore it melts the ice faster, however, Rock salt is mostly preferred for de-icing because it has particles as large as 5mm. It also depends on the temperature, temperature makes a huge difference, at what temp the project going on.
I believe stable salt melts ice the fastest because I, myself, had done this experiment and table salt worked the best. You can also check online. It says table salt works the best because it is finer and the more finer something is, means it has more surface area. If something had more surface area, it means the salt can touch more parts of the ice and come in contact with it
My son and I are doing this project now. His hypothesis was that table salt will melt the ice the fastest because it is finer. Oddly enough, 10 minutes have elapsed and rock salt seems to be the one melting ice the fastest. Now my question is why this is so. We looked at all the ingredients list and everything except rock salt has some kind of anti caking agent....does this affect the melting process?