Evaluation methods of asphalt pavement service life
A functional relationship of the dynamics of asphalt concrete pavement condition and its thermodynamic and thermophysical functions and parameters (Helmholtz's energy, internal energy, entropy, specific heat, etc.) is described. Based on this functional relationship, novel approaches to the estimation of asphalt pavement lifetime are proposed. The dependence of pavement lifetime from the basic thermodynamic parameter – specific heat (for the determination of which expensive and complicated equipment is not required) is derived. The statistical approach to determination of pavement lifetime, based on the analysis of the temporal changes in the spatial distribution of the basic parameter (specific heat) is proposed. Overall, three alternative but complementary approaches are described to determine pavement service interval using either a molar weight, a change of free energy, or the uniformity of the basic parameter – specific heat based the index of thermophysical uniformity (a dimensionless coefficient). Numerical pavement lifetime values suitable for exploitation under the Russian service conditions (transportation and construction terms) are calculated analytically. Regardless of the approach used of the calculated pavement lifetimes are of the same order of magnitude. These initial results are quite promising and offer a new thermodynamic approach to the estimation of pavement condition and its useful lifetime. This practical new approach can be utilized to replace or complement the traditional "mechanical" and geo-radar methods.