Curl and Warp Analysis of The LTPP SPS-2 Site in Arizona

RECOMMENDATIONS

This report demonstrated the potential for isolating the effect of curl and warp from other sources of roughness in the study of long-term pavement performance due to the strong statistical relationship between changes in IRI and changes in PSG. This report also demonstrated that long-term increases in IRI may be caused solely by changes in curl and warp and do not necessarily indicate structural failure or increased surface distress. However, the statistical methods used in this study required a high volume of profile measurements. Refinement of the methods for more general applications with broader validity and less ambitious data requirements requires further study. The following investigations are recommended:

• Study structural models other than the original Westergaard equations that may improve the prediction of slab profiles near the joints on pavements with dowels. This may also permit the theoretical determination of the IRI-PSG slope and reduce measurement effort.
  
  
• Apply the method to other SPS-2 and General Pavement Studies (GPS)-3 sites to generalize the IRI-PSG relationship for each pavement design. This would reduce the measurement effort needed to apply the methods investigated in this study and provide the same detailed assessment of the long-term behavior of pavements at other SPS-2 and GPS-3 sites.
  
  
• Seek a refinement to the method that permits full analysis on high-strength sections and on pavement for which curl and warp is a small contributor to IRI. This may require an alternative method of estimating the dependence of IRI on PSG or the development of an alternative to PSG.
  
  
• Refine the process of obtaining the radius of relative stiffness and quantify the sensitivity of the results to the quality of the estimate.
  
  
• Investigate a version of the method that relates raw PSG, rather than average absolute PSG, to IRI.
  
  
• Relate PSG to environmental factors.