I would like to patch a crack in my cement bird-bath........

I've made 4, but when making this one I neglected to work out all the air bubbles. So, I surmise that water got in the space/s, froze, & cracked it during winter.

It is my largest, & the deepest of my shallow bird-baths. I wanted to leave it extra rough, to give hummingbirds & bees better foot-holds.

I would like to know whether I can effectively use just sand, cement, & water to patch it, or would that not work for some reason? What would work best? I do not plan to seal it. None of the others have been sealed, & none of them have cracked, though some are older & have been used longer, even in winters when we have had a freeze.

Thank You!