Proper use of a 16' straightedge for pavement smoothness
Proper use of a 16' straightedge for pavement smoothness
(OP)
Does anybody know an authoritative source indicating how to properly use a 16' straight edge? The use is for measurement of asphalt pavement smoothness at an airport under the FAA P401 specification. I'm finding it surprising hard to demonstrate that the proper use is to measure under the straight edge when placed on the pavement supported along its length rather holding one end down and using it to extend over a grade break and then measure.





RE: Proper use of a 16' straightedge for pavement smoothness
When you have the straightedge resting on the 1/4" blocks, there should be no high spot that touches the underside of the straightedge. Correspondingly, there should be no low spot that would allow the insertion of the 1/2" check block. You can actually purchase shims of various thicknesses that are configured like a "feeler gage" to do this, but you should still support on each end with blocks the thickness of the tolerance.
Allowing the straightedge to teeter on the high spots or cantilever over sections is a poor way to check.
RE: Proper use of a 16' straightedge for pavement smoothness
RE: Proper use of a 16' straightedge for pavement smoothness
The Florida DOT has a similar procedure for calibrating a rolling straightedge against a manual straightedge, but it doesn't give this as a procedure for measuring.
I like it because it is logical and intuitive.
RE: Proper use of a 16' straightedge for pavement smoothness
RE: Proper use of a 16' straightedge for pavement smoothness
Using the shim method or shim/feeler gages you can appropriately quantify both the high and low spots relatively.
RE: Proper use of a 16' straightedge for pavement smoothness
You'll want to try to "bump the mat" alongside the finish roller in an attempt to work out any bumps if possible. Elsewise we were just dinging them after the fact with a set deduction, say 1 ton per bump. I have seen some recent projects where the Contractor bump ground after the fact but that really doesn't look good on a fresh overlay.
The 16' rolling straight edge is also handy to check against the 30' rolling profilograph when you have to go back and grind bumps out on concrete pavement after you reduce those results. Much easier to lug around than that A-framed monster.