Curl and warp analysis of the LTPP SPS-2 site in Arizona

Abstract

This study examined the roughness and roughness progression of 21 test sections on the LTPP SPS-2 site in Arizona over the first 16 years of the experiment. The site included 12 test sections from the standard experiment and 9 supplemental test sections selected by the Arizona Department of Transportation. Traditional profile analyses revealed roughness caused by transverse and longitudinal cracking on some test sections and some localized roughness caused by built-in defects. However, the analyses showed that curl and warp contributed to, and in some cases dominated, the roughness on many of the test sections. In addition, roughness did not increase steadily with time because of diurnal and seasonal changes in slab curl and warp. This study applied objective profile analyses to quantify the level of curl and warp on each section. These automated algorithms estimated the gross strain gradient needed to deform each slab into the shape present in the measured profile and produced a pseudo strain gradient (PSG) value. The levels of curl and warp within each profile are summarized by the average PSG value. For the jointed concrete test sections, variations in average PSG over time explained many of the changes in roughness over time. This included diurnal variations in slab curl, which often caused the overall progression in roughness to appear disorderly throughout the experiment. PSG analysis also revealed that the overall level of curl and warp increased throughout the life of the experiment, with commensurate increases in the roughness. This limited study demonstrated the potential value of applying the methods herein to other jointed portland cement concrete pavements, including other SPS-2 sites.