said by zach3:
Why not clean the concrete ceiling and Ram-set a piece of 3/4" plywood with some PL 400 to the ceiling that is slightly larger than the footprint of the projector.
Then paint or stain the plywood and use some wood screws to attach the projector.
Because that would require you to ram set the plywood. Plus PL400. Then paint or stain it. Then secure it with 3/4" wood screws. All your work is to just to get to the same point you are at when you started...attaching the projector to something.
Call me silly, but a couple of tapcons is going to be easier, faster, hold just as well. Plus little risk of spalling so when the time comes to take it down, you can and not leave a decent divit. Plus Tapcons can be installed by a standard drill if you had to. No Ramset to buy. Also no risk of the nail not driving fully and sticking out loose.