Construction-Related Temperature Differentials in Asphalt Concrete Pavement: Identification and Assessment

Abstract

Numerous Washington State Department of Transportation (WSDOT) paving projects have experienced a cyclic occurrence of premature failure of open-textured asphalt concrete (AC) pavement sections by fatigue cracking, raveling, or both, generally called “cyclic segregation” or “endof-load segregation.” This resulted in an initial study in which mat temperature differentials were observed during laydown. In turn, this led to the current study and the reported results. Pavement temperature differentials result from placement of a cooler portion of the hot-mix mass into the mat. This cooler mass generally constitutes the crust, which can develop during hot-mix transport from the mixing plant to the job site. Placement of this cooler hot mix can create pavement areas near cessation temperature that tend to resist proper compaction (they may also exhibit tearing or roughness or appear to be open textured). These areas were observed to have decreased densities and a higher percentage of air voids (higher air voids). Four 1998 WSDOT paving projects were examined to determine the existence and extent of mat temperature differentials and associated material characteristics. An infrared camera was used to identify cooler portions of the mat, which were then sampled along with normal-temperature pavement sections. Gradation and asphalt content analysis showed no significant aggregate segregation within the cooler areas. However, these cooler portions of the mat consistently showed higher air voids than the surrounding pavement. On the basis of numerous studies that have related AC deterioration and high air voids in a mix, it is known that the areas of a mat with higher air voids may experience premature failure compared with the time to failure of the mat as a whole.

Use of infrared thermography for assessing HMA paving and compaction

“…the maximum differences in temperature between any two points within the specified test volume at a given instant, during paving and compaction process. Commonly, temperature differentials are associated with poor compaction, segregation and premature distress of asphalt pavements (Elsafey et al, 2009;Herold et al, 2008;Mahoney et al, 2000;StroupGardiner et al, 2000). Considering as representative measure the mat surface temperature, the two types of paved HMA (i.e.…”

“…Temperature differentials in the mat during HMA paving can result in substantial density differentials (Henault and Larsen, 2006;Willoughby et al, 2002;Mahoney et al, 2000). Research in this area has emphasized the identification of cooler areas in the mat and its relationship with final HMA density.…”

“…IRT can be defined as the science of the acquisition and analysis of data from non-contact thermal imaging systems and allows continuous real time data collection during both the laydown and compaction process. In the past, a number of research studies have been conducted that attempt to explain thermal variations in field observations of asphalt concrete pavements (Mahoney et al, 2000;Stroup-Gardiner et al, 2004). Several researchers have emphasized the segregation occurring during the laydown process due to the lack of mix temperature homogeneity (Sebesta et al, 2006;Stroup-Gardiner et al, 2000).…”

The Influence of Water on the Heat Loss of Hot Mix Asphalt

“…The compaction effort and time can be relatively easily controlled by adjusting the number roller passes on the same path during a given time period. Conversely, it is most difficult to control the temperature during the process, especially when weather conditions vary [5,7,8].…”

The heat exchange in the edge area – the problem of hot mix asphalt compaction

“…Changes in the temperature of HMA while laying it out are dependent on the speed of heat flow in the layer (expressed by λ ratio) and the capacity to collect it by the surrounding environment (characterised by the α ratio). The description of the phenomenon described in the literature concerns only areas near the center of the layer (Mahoney et al 2000;Mieczkowski 2006;Timm et al 2001). The obtained results not used for the evaluation of heat loss directly on its edge, because of omitting additional surface of heat flow (side edge).…”