DIFFERENTIAL THERMAL-EXPANSION AND CONTRACTION - A MECHANISTIC APPROACH TO ADHESION IN ASPHALT CONCRETE

The difficulties associated with developing reliable roadway failure p rediction models are due to the lack of sound theoretical analyses to assess the true causes of pavement distress. Low-temperature cracking and stripping may be two of the causes of pavement distress that are d ifficult to predict. This paper introduces a simple mechanistic approa ch that describes the response of the asphalt-aggregate system to temp erature changes. The concept recognizes the thermal incompatibility be tween asphalt cement and aggregate. Owing to the considerable differen ce in the coefficients of thermal expansion of aggregate and asphalt, the asphalt matrix will attempt to contract more than the aggregate du ring thermal cooling. An analytical model was derived to estimate the thermally induced stresses resulting from differential thermal contrac tion. The experimental investigation, which is part of a study investi gating adhesion, verified the findings of the analytical approach. Fin dings from this study explained field and laboratory observations made earlier by other investigators. These observations were associated wi th asphalt concrete low-temperature performance and its resistance to stripping.