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In countries that suffer from large amounts of rainfall, the asphaltic wearing sur­faces are often constructed of open graded asphaltic mixtures. The high perme­ability of these wearing surfaces ensures a fast drainage of the water away from Fig. 5.15 (a) bad road visibility conditions (b) hydroplaning and ‘splash and spray’ (Erkens, 2005). Reproduced by permission […]

Performance characteristics of bound pavement layers are known to be influenced by water-borne pollutants that cause changes in mechanical behaviour, ageing and degradation. With the exception of Portland cement concrete (PCC) pavements, this has not yet received much attention. Asphalt pavements are not seriously affected by inorganic pollutants, but most of the organic chemicals, including […]

The motivation for the following micro-scale finite element simulation, is the on­going discussion about cohesive versus adhesive failure mechanisms in asphaltic mixtures. It is the authors’ belief that, depending on the ability of the individual components and the bond between them, either one of these failure mechanisms may be dominant. It is, therefore, of paramount […]

Moisture diffusion measurements are still not performed very commonly for as­phaltic materials. There are currently two main test procedures being utilized. The first is an overall measurement of the increase of weight as a sample is ex­posed to a controlled moisture conditioning (Cheng et al., 2003). The second is a slightly more complicated procedure using […]

Because water-induced damage influences the dry response of the material, the effects of the physical processes must be coupled with a three dimensional elasto- visco-plastic constitutive model for mastic response (Scarpas et al., 2005). Mastic in asphaltic mixtures is known to be a material whose behaviour, depending on strain rate and/or temperature, exhibits response characteristics […]

The existence of a water flow through an asphaltic mixture may cause desorption of parts of the mastic films which are in direct contact with the water flow, Fig. 5.8(a) carrying away elements of the bitumen[8] by advection (see Chapter 6 for a fuller definition of advection). Exposure of an asphaltic mixture to stationary water […]

One of the important realizations is that the problem cannot be solved by mechanical considerations alone. Clearly, water has an effect on the material characteristics of the asphaltic components and their bond, even without mechanical loading. There­fore, both physical and mechanical water damage-inducing processes are included in the model. Another realization is that, in order […]

5.5.1 Introduction: The Problem of Water for Road Surfacings Practice has shown that asphaltic wearing surfaces which are exposed to water generally start losing aggregates prematurely through a damage phenomenon that has become known as asphaltic ‘stripping’ or ‘ravelling’. Stripping is generally at­tributed to water infiltration into the asphaltic mixture, causing a weakening of the […]

Because cracks play such an important part in allowing water to enter a pavement through the surfacing, laboratory assessments of the permeability of intact asphaltic mixtures are not overly useful. Therefore, a range of techniques have been developed to assess permeability by infiltrating water into the pavement surface from a device which acts over a […]

In distressed pavements a large proportion of ingress may be through cracks, even if the intact material is relatively impermeable. It has been suggested that there are four factors which influence infiltration rates in cracked asphaltic pavements (Ridgeway, 1976): • the water-carrying capacity of the crack or joint, • the amount of cracking present, • […]