I have read that for the end of concrete floor beams with exposed rebar that are on the outside of the building which may get wet the beams should be protected, either with a mastic type material or an end cap.

 

Any idea of a product that can be painted on?

I used Iko Bitument paint.

K Kaps look cool, but could not find any stock and probably they make sense when dealing with 10s or 100s of beams and time saving is measureable.