Prime concrete slab with what before quarry tiles

Almost finished my outside bbq/pizza oven combo outside. I’ve made countertops from old 3x2 concrete slabs and I’ve just bought and sealed some new cheap 8mm quarry tile look-a-likes. Also bought some powdered S2 adhesive as this was recommended for outside use.

The bloke at the shop suggested I PVA the concrete slabs prior to tiling. Just wanted to check on this as PVA as a primer can be a touchy subject.

Thoughts appreciated

No. Not PVA. It becomes active when wet and will cause the adhesive to de-bond in wet weather. It will also reactivate when it comes into contact with wet adhesive, you then get a chemical reaction with the portland cement, which produces Acetic Acid which will prevent the adhesive from hydrating correctly.

It needs to be an acryllic sealer like BAL APD or Ardex P51, or any brand of an SBR Primer (for your guarantee, i'd suggest the same brand as the tile adhesive you intend to use).