I know that this is an old post, but I will include my information in case anyone stumbles across it.
We've been using automotive bondo for over 50 years to repair concrete statues at our store, it is perfect because it provides a strong bond, dries fast (usually within 5 minutes) and it doubles as a filler. As it cures bondo can be cut and or shaped and then sanded for a smooth finish. Bondo can be painted with regular exterior latex paint after your repairs are finished, there is no need to prime or seal concrete (this acutally holds in moisture that should naturally come out of concrete) just make sure the piece to be painted is warm, dry and dust free.
Hope these tips can be of use
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