CA activator is more appropriately called "accelerator". CA will cure without any additional chemicals, although the more viscous it is, the longer it will take to fully kick without accelerator. It's worth having a bottle on hand, even if you rarely use it. It won't go bad. Epoxy is good for structural joints, or when you need to fill a small gap, but (just my opinion, I know many will argue) skip the 5 minute epoxy... the slow cure/24h stuff is much stronger, especially when working with porous materials.