U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
|This report is an archived publication and may contain dated technical, contact, and link information|
Publication Number: FHWA-HRT-04-032
The knowledge of pavement layer material properties is important for modeling pavement behaviors. The following are summaries from several several LTPP material studies.
Pavement material properties such as stiffness (modulus of elasticity) can be backcalculated from FWD layer-deflection data by three approaches: the slab on elastic solid (ES) foundation, the slab on dense liquid (DL) foundation, and the elastic layer procedures. While the ES and DL approaches are used for rigid pavements only, the elastic layer approach can be used for both rigid and flexible pavements.
The LTPP program conducted two studies to demonstrate how the LTPP deflection data can be used for backcalculation of pavement layer material properties. In the first study, the ES and DL approaches were used; the elastic layer approach was used in the second study for backcalculation of pavement material properties. The following findings are obtained from the two studies.
The majority of the backcalculated PCC moduli using either the ES or DL subgrade approach fall in the range of 25,000 to 55,000 MPa (3,625 to 7,977 ksi). It seems that the two backcalculation approaches can generate acceptable PCC moduli.
The PCC moduli obtained by the ES approach are consistently lower than the DL approach. This is expected because an ES foundation provides significant shear load redistribution while the DL approach provides no shear load redistribution.
For treated base materials, the backcalculated base moduli were found to be within reasonable ranges using either the ES or DL approach. The backcalculated base moduli obtained by the ES approach appear to be higher than the DL approach.
For untreated base materials, the backcalculated base moduli obtained by the ES approach are usually lower than the DL approach. Base moduli backcalculated using either the ES or DL approach fall in reasonable ranges.
Report No. NCHRP 20-50(9)
The feasibility of using FWD data as a quality control and qualityassurance measure during the construction of pavement structures has been an interesting topic. The key findings of NCHRP Project 20-50(9) are presented below.
Topics: research, infrastructure, pavements, concrete, design, jointed, fiber-reinforced polymer, FRP, dowels
Keywords: research, infrastructure, pavements and materials,Distress, LTPP, pavement, cracking, rutting, faulting
TRT Terms: research, facilities, transportation, highway facilities, roads, parts of roads, pavements