Paving on 57 stone
Paving on 57 stone
(OP)
I am currently designing a pervious paving parking lot for a fire station. Due to the loading, I'm only using pervious asphalt in the automobile parking bays and standard asphalt in the drive lanes. My question is whether it will be stable if they pave directly on the 3-foot thick base of 57 stone with standard asphalt? If not, would a choker course help or do I need to look at getting the detention volume elsewhere?





RE: Paving on 57 stone
RE: Paving on 57 stone
This is commonly done with pervious pavement in parking areas and low-volume travel lanes- 57 stone is used as the base course with pervious asphalt as the surface course. However, since pervious asphalt does not have the load bearing capacity of dense-graded asphalt, I was trying to decide whether I could the dense-graded asphalt in the travel lanes, how well it can be compacted over 57 stone and whether the 57 stone was stable enough for longer-term loading with the fire engines.
RE: Paving on 57 stone
RE: Paving on 57 stone
RE: Paving on 57 stone
RE: Paving on 57 stone
If the pavement section is improperly designed, a saturated subgrade can be a nightmare. However, I'm using 3 inches of asphalt on top of 30 inches of No. 57 stone with triaxial geogrid for additional stability and an unwoven geotextile to prevent soil intrusion. The soil is a clayey silt with low plasticity and can drain a 10-year rain event in 2 days.
I had thought about using pervious pavers and have used them for emergency access for vehicles before, but the fire department is concerned with the maintenance, upkeep and general aesthetics of the parking area.
I really appreciate the comments, but my specific question was regarding whether dense-graded asphalt over washed stone would stand up to fire truck loads. My educated guess is that it would, but I would feel much more comfortable if I could get the opinion of someone who had experience with this specific situation.
Thanks,
CJ
RE: Paving on 57 stone
RE: Paving on 57 stone
Based on that and the turning movements that will be happening in the drive lane, I've decided to use concrete for the drive lane. I already have the pavement section design for the rest of the parking lot done with concrete and the 30" stone base should be much more stable than what is underlying the rest of the fire station. I'll just use the pervious asphalt pavement in the parking stalls.
Thanks for your help,
CJ
RE: Paving on 57 stone
RE: Paving on 57 stone
I'm not sure how much of a difference it makes, but I've modified the pavement section somewhat- in the drive aisle it will be 6" concrete over 2" of #57 stone over 28" of #2 stone over Tensar TX-5 triaxial geogrid over a Mirafi unwoven geotextile over the uncompacted subgrade. The parking stalls will only carry passenger car and truck loads and will be 2.5" of pervious asphalt over a similar pavement section (with 31.5" of #2 stone).
CJ