Whenever painting concrete or cement such as slab or steps,
concrete or cement blocks or walls and footings, after first
washing and rinsing the surface, always wipe the surface again
with straight (undiluted) white vinegar. Let the vinegar dry
on the surface and do not rinse off. Then paint the area
immediately after the vinegar is dry.
Your paint will last nearly twice as long, even with heavy foot
traffic, and any decorative painting will be less prone to
blistering or peeling from sunlight.