Pavement surface characteristics

Before referring to and describing the devices used for functional evaluation of the pavement, general issues regarding pavement surface characteristics will be discussed in the following paragraph. 

The pavement surface characteristics that are closely related to the pavement functionality are the ones related to its geometric profile on the vertical level. 

The pavement surface characteristics affect not only driving safety and comfort but also the environmental pollution (mainly noise) and the vehicle operating cost (maintenance cost, tyre replacement cost, wasted fuel cost). 

A pavement surface should primarily have a good friction skid resistance (good micro-and macro-texture) for the avoidance of accidents, as well as good evenness in the transverse and longitudinal direction for comfort during driving and additional driving safety. 

Additionally, the pavement surface should not generate high noise levels and should have good light reflective properties. For the latter, the micro- and macro-texture in conjunction with the water withholding at the surface are the basic affecting factors. 

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Martin J.-M., F. Menant, and F. Lepert. 2012. Information relating to the measurement of the longitudinal evenness in France. 7th Symposium on Pavement Surface Characteristics SURF 2012. Virginia Tech Transportation Institute (VTTI). 

CEN EN 13036-1.2010. Road and airfield surface characteristics - Test methods - Part 1 Measurement of pavement macrotexture depth using a volumetric patch technique. Brussels CEN. 

At the end of the design life, the pavement is expected to fail owing to fatigue cracking or surface deformation. During the lifetime of the pavement, the surfacing material is expected to be rehabilitated to meet surface characteristic requirements. The frequency of the rehabilitation depends entirely on the life expectancy of the surfacing material used in relation to traffic volume. 

The surfacing material should provide a pavement surface with long-term good surface characteristics, particularly anti-skidding properties. The asphalts recommended to be used by the methodology are the following ... 

Functional evaluation considers the surface characteristics of a pavement and is user related. Surface characteristics include longitudinal evenness (smoothness), skid resistance, rutting, cracking or any other surface distress that affects riding quality and safety. Functional evaluation is used to decide whether the pavement needs to be maintained, rehabilitated or reconstructed essentially, the necessity for intervention and its type is decided. 

The most objective assessment of functional pavement condition evaluation is conducted using purposely built devices that record the pavement s surface characteristics, in particular evenness, skid resistance and texture depth. These devices are self-mobile, mobile or portable when a short length of road pavement has to be surveyed. 

Figure 16.20 Explanation of texture depth determination and measuring device. (Adapted from CEN EN 13036-1, Road and Airfield Surface Characteristics - Test Methods - Part I Measurement of Pavement Surface Macro-Texture Depth Using a Volumetric Patch Technique. Brussels CEN, 2010. With permission [ CEN] and ASTM E 965, Standard Test Method for Measuring Pavement Macro-Texture Depth Using a Volumetric Technique. West Conshohocken, PA ASTM International, 2006.)...

The laser devices are attached either at the front or at the rear of the vehicle and scan the pavement surface. These vehicles, apart from recording the pavement texture profile, also record other surface characteristics such as longitudinal profile, transverse profile (rut depth) (see Figure 16.30) or even surface cracking (Figure 16.36). 

Flowever, both terms, unevenness and roughness, express the same surface characteristic, namely, the deviation of a pavement surface from a true filtered planar surface. 

CEN/TS 13036-2. 2010. Road and airfield surface characteristics — Test methods. Part 2 Assessment of the skid resistance of a road pavement surface by the use of dynamic measuring systems. Brussels CEN. 

CEN/TS 15901-1. 2009. Road and airfield surface characteristics - Tart 1 Procedure for determining the skid resistance of a pavement surface using a device with longitudinal fixed slip ratio (LFCS) RoadSTAR. Brussels CEN. 

The functional evaluation of the pavement is usually carried out by a visual condition survey, coring and the use of necessary devices measuring surface characteristics such as... 

Abrasion and erosion. The dust-loaded wind has an erosive action and contributes to a physical disintegration of rock surfaces or to a polishing of the components of the desert pavement, giving them a characteristic patina desert varnish) and shape (ventifacts). 

The pavement modelling allows to introduce into the model the temporal evolution of the size distribution of materials at the bed surface. By a progressive decrease of the probability density function of the lift force, this model successfully predicts the temporal decrease in mass flux that occurs with the presence of coarse particles at the surface. The rate of this decrease depends on the flow velocity and the characteristics of the particles. In order to improve the accuracy of the estimation of fugitive particle emissions with a wide size distribution, it is necessary to take into account this temporal decrease. 

The typical property of PA is the high air void content (usually >18%), as well as the high number of interconnecting voids. Because of the above two characteristics, there is quick drainage of surface rainwater and a reduction of the tyre/pavement. 

Later on, Dauzats and Rampal (1987) published results that surface-initiated cracks in France were initially caused by thermal stresses and then further propagated by traffic loads. Gerritsen et al. (1987) reported that pavements in the Netherlands were experiencing premature cracking in the wearing courses and those observed outside the wheel paths were associated with asphalts having low strength characteristics at low temperatures. 

The following are the properties required for a geosynthetic to be used in pavement rehabilitation or new pavement asphalt works tensile strength and elongation (in both directions), bitumen retention, durability, alkaline resistance (in case a geogrid or a geocomposite is used over concrete surface) and melting point, to name a few. Property requirements and other characteristics are specified in CEN EN 15381 (2008), ASTM D 7239 (2013) or other relevant standards. 

In the case of the polymer-air interface, the ability to stick to the surface, resist wear or have a certain aesthetic characteristic can be dependent on the way the polymer molecules are organized at the interface. A number of physical phenomena are related to our understanding of the properties of an interface spreading of oil on a surface, adhesion of two bodies in contact (e.g. chewing gum sticking to a pavement), interaction of fluids with biological materials (e.g. blood in arteries), etc. 

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