Asphalt thickness determination

[aaronivey]

Hello all,

I am constructing a private asphalt road to serve a small residential neighborhood in Oklahoma. City requirements are forcing me to construct the road in such a manner that "it can withstand 70,000-75,000 pounds", which they claim is the weight of our fire trucks. From a practical standpoint, I will almost certainly never have a fire truck on the actual road (there will only be 6 houses), but we will have garbage trucks on it once a week, which are probably in a similar weight class.

I am trying to determine how thick my asphalt needs to be in order to be able to have a local structural engineer sign a letter certifying that my street design will suffice for that weight load. We are using 5% CKD from a pre-calciner plant for stabilization and our sub-base is a sandy/clay (mostly clay).

For cost purposes, I am hoping to get a certification for 4 inches, but could do 5 inches if necessary. Six inches gets way outside of our budget, so I'm hoping I can avoid that at all costs, no pun intended.

 

[bridgebuster]

Try this link, free pavement design. I'm not a pavement designer but 5" sounds like it should work. The key is a well-compacted sub-base.

Link

 

[Ron]

Asphalt pavement thickness design is not based on the total load of a vehicle as they have given you. It is based on axle loads and the number of axles. A typical fire truck has extremely high axle loads, but because they infrequently traverse the pavement section, particularly a limited access residential pavement, their effect on the pavement is generally ignored. The repetitive loads from garbage trucks, delivery trucks and cars should be your concern.

Build the pavement structure from the bottom up as bridgebuster noted. Stabilize the top 12 inches of subgrade with the calciner waste, but make sure it does not cause expansion when wet. Provide a good base material, typically a graded aggregate base about 6 inches thick, then you can get by with only 2 inches or so of asphalt. This is typical of a light duty pavement and will handle your garbage trucks and delivery trucks, plus the occasional fire truck.

All soil layers should be well compacted to at least 98 percent of the Modified Proctor maximum dry density. Asphalt should also be well compacted to about 95 percent of its theoretical maximum density.

Most structural engineers don't do pavement design so I doubt you'll find a local structural engineer who will "certify" your design. I just happen to be a structural engineer with a lot of geotechnical and pavement experience as well, so have no issue with doing pavement design. You will likely have to get a local general civil engineer or geotechnical/materials engineer to review and approve the design.