No padding, except for that thin plastic layer of artificial "grass" that would give you severe skin abrasions.
That, plus the seams where the turf pieces were stitched together, would often times come apart. That horrible turf at Veteran's Stadium in Philly ended many careers, including the Bears' #1 wide receiver, Wendell Davis. I remember his jumping to catch a pass, only for his foot to get stuck in the ripped seam, and he horribly ripped apart his knee.
Some turf fields, such as Dallas' stadium, were better padded, but for the most part, playing on Astroturf would shorten your career by a large chunk by causing all of that wear and tear on your knees.