Differential thermal expansion and contraction: a mechanistic approach to adhesion in asphalt concrete

Abstract

The difficulties associated with developing reliable roadway failure prediction 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 difficult to predict. This paper introduces a simple mechanistic approach that describes the response of the asphalt–aggregate system to temperature changes. The concept recognizes the thermal incompatibility between asphalt cement and aggregate. Owing to the considerable difference in the coefficients of thermal expansion of aggregate and asphalt, the asphalt matrix will attempt to contract more than the aggregate during thermal cooling. An analytical model was derived to estimate the thermally induced stresses resulting from differential thermal contraction. The experimental investigation, which is part of a study investigating adhesion, verified the findings of the analytical approach. Findings from this study explained field and laboratory observations made earlier by other investigators. These observations were associated with asphalt concrete low-temperature performance and its resistance to stripping. Key words: differential thermal contraction, asphalt matrix, localized damage, stripping.