While I am not a "concrete guy", I am a structural engineer and on my driveway, I used a product from Sika Corporation which is a leading manufacturer of a wide variety of conrete topping products.
Sikagard 701W is a solvent-free concentrate of silane modified siloxane emulsion. When diluted the liquid forms a water and chloride-ion repellent impregnation specifically formulated to seal absorbent cementitious surfaces and other masonry substrates.
This shit works very well but it is not cheap. You can get more info by searching for "Sika".