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This paper addresses the measurement and modelling of the damaged properties of asphalt mixtures including the fracture, healing and viscoplastic deformation of the asphalt mixtures in both tensile and compressive loading as being affected by their composition and conditioning with ageing and exposure to temperature and moisture. An energy-based mechanics is applied to obtain the material fundamental properties such as surface energies, bond energies, anisotropy, yield functions and plastic potential functions that are valid for actual asphalt mixtures, viscoelastic crack growth criteria under both tensile and compressive loading, a simple mechanics-based method of determining the fatigue endurance limit, and the measurement and prediction of healing in restoring the damage done by fracture. Healing is antifracture and cracking is the net result of the interplay of these two complimentary mechanisms. Because fracture in asphalt mixtures is not the growth of a single crack but the simultaneous growth of multiple cracks that start out as air voids, this fact leads to the use of the growth of damage density to characterise fracture in an asphalt mixture. It was discovered that the form of Paris' law applies to the growth of damage density of asphalt mixtures in both tensile and compressive loadings. The importance of this fact lies in many developments from this discovery, e.g. compressive monotonic loading of cylindrical test samples permits a direct determination of the Paris' Law coefficient and exponent. In all cases, measured material properties are presented as they vary with mixture composition and with conditioning such as moisture and ageing, both in the lab and in the field. The measurements of these properties are made simply, quickly and accurately by the use of mechanics so that an entire characterisation of the properties of an asphalt mixture in tension and compression can be completed in the space of one day. The net effect is to reduce the efforts expended in the lab and the systematic error due to the assumptions made by the existing models and simultaneously to increase the efficiency and cost-effectiveness of materials testing and raise the reliability of the design of mixtures, pavement structures and specifications and the prediction of the life cycles in as-built pavements. [ABSTRACT FROM AUTHOR]

Cracking in asphalt pavements is the net result of fracture and healing. The ability to accurately measure and predict the appearance of cracking depends on being able to determine the material properties that govern the rate of development of these two contrary aspects of cracking. This study is devoted to identifying the datum material properties in undamaged samples. It will make use of viscoelastic formulations and of well-known mechanics concepts the way in which these properties are altered by the composition of the mixture. Also introduced in this study is a process that makes extensive use of the pseudo-strain concept in decomposing the strain components. One of the many benefits of this approach is the ability to measure the fatigue endurance limit of an asphalt mixture with a simple test that requires only half an hour. The study begins with a detailed discussion of these concepts and properties and the test methods that simply and accurately measure them. One of the great advantages of using mechanics is that it provides a rapid and efficient way to predict the rate of appearance of the two aspects of pavement cracking, fracture and healing. Mechanics requires the use of material properties. An accurate and efficient determination of undamaged material properties is fundamental and important to the prediction of the performance of asphalt mixtures. It is found that the undamaged properties of an asphalt mixture are different when they are loaded in tension or in compression and this distinction is important. This study addresses the efficiency of the laboratory testing methods, and the effects of the volumetric material components and environmental factors such as temperature and ageing on the undamaged material properties. It also introduces the non-destructive tests that must be made in order, subsequently, to measure the damaged properties of the same materials. [ABSTRACT FROM AUTHOR]