No abstract

No abstract

Accurate measurement of pavement thickness is an essential aspect of the quality assurance of new pavement construction. Current coring methods are time consuming and provide a very limited representation of the overall pavement structure. The objective of the work described in this paper has been to demonstrate the use of non-destructive evaluation (NDE) methods for rapidly determining the average pavement thickness on a newly constructed section to within 2.5 mm of the true value, without extensive reliance on cores. The effort has considered ground penetrating radar (GPR) and impact echo methods applied to both asphalt and concrete pavement, and has included laboratory and field-testing, with field correlations based on 172 cores. The results show that the 2.5 mm accuracy objective can be met for asphalt pavement, but that accuracy on concrete is limited to 4 mm. The paper describes the techniques that were evaluated, the testing that was conducted, and the results of correlation with core data.

No abstract

Delamination that occurs because of layer debonding or stripping between layers of hot-mix asphalt can cause distresses such as longitudinal cracking in the wheelpath and tearing in the surface. Because these distresses cannot be detected by visual inspection of the pavement, highway agencies are interested in finding nondestructive methods for detecting delamination to maintain roadway networks. A study evaluated an ultrasonic tomography device for detecting the type and severity of delamination with various focusing techniques. A comparison of blind ultrasonic tomography testing results versus construction of bonded and debonded conditions showed that ultrasonic tomography could detect delamination between new and old asphalt layers, as well as delamination of lifts within new asphalt pavement. B- and D-scan methods with the focusing technique of synthetic aperture were able to identify delamination between new and old asphalt interfaces, and a new focusing method developed at the University of Minnesota was used to identify delamination within asphalt lifts.