extracting screws from concrete

[professional]

I went on a little mission the other night to uncap some ledges and found that my drill wouldn't extra the screw from the ledge. it may have been a number of factors like:

the screw/cap being there for the past 3+ years
my drill not fully charged
the screws being rusted

but my main concern is whether or not the screws will even come out of the ledge. if anyone on here works with that type of stuff I'd appreciate you chiming in on this. The drill is a black and decker CD180G 18volt, I tried finding the amount of torque it has but had no luck.

Thanks dudes