I restore floors, although mostly timber, I have done a few concrete grinding and polishing jobs too.
Sealing a concrete/cement floor can often make it more slippery. Unsealed concrete can be grippy unless its been ground, then it has a smoother finish. Some concrete can be permanently dusty making it slippery. Sealed floors have some grip, but if they get wet they become extremely slippery. Adding grit to sealers/polyurethanes is a great way to give your floor some more grip, but the courser the grit and the grippier you make it, will increase tyre wear and hurt more when you crash.
I'd vaccuum the concrete, buy some concrete polyurethane sealer and add some fine sand to the mix, doing two coats.