What size hole do I need in masonry for an anchor that takes a 1/2" thread?
Those hangars are designed to go into wood, but you should be able to install into concrete using lag shields, just as you would use with a lag bolt. My only concern is that lag bolts have a standards and ratings, where this ladder hangar might be of unknown strength, and could simply shear off in the lag shield. I wouldn't park my car next to or beneath it.

The lag shield has a specified hole size required, which should be documented, such as this one.