Hello all I'm new to everything concreting and just wanted some help/advice I make atlas stones for strongman lifting they are round cement balls (I don't make money off it) at the moment I use just a 40mpa pre mix bags of concrete cause some balls weigh close too 190kg and are dropped from shoulder height onto the ground, they turn out good but have a lot of air bubbles holes through out and on the surface. Also after they are released from the mould they are kept wet for a week to help them cure I was wondering, what's the best way too get strong cement and a smooth finish, I've herd that bycol added to cement will make it easier to get the air out I've also got a second hand small cement vibrator, what kind of mix and process do people use too make smooth strong precast cement? Any help would be appreciated thanks