Pavement Texture and Maintenance

In order to sustain the functionality of pavements for a longer time frame, it is necessary for them to be maintained. The two methods of maintenance pavements usually undergo are Structural and Operational maintenance.

Structural maintenance entails carrying out works that maintain the quality and safety characteristics of the pavement surface. Structural maintenance is vital as pavement break-up results in surface roughness and an increase in loose particles, which become a safety hazard to both aircraft and motor vehicle users.

Examples of this type of work are crack and joint sealing, patching, paint marker removal, etc. Operational maintenance entails activities that are necessary from time to time and are related to safety of daily operations. Examples of these types of work are rubber removal, sweeping and cleaning, snow removal, wildlife and bird control, etc.

Of particular interest in structural maintenance is the removal of rubber and paint marker, oil and loose particles from pavements to maintain an acceptable friction value. If this is not done on regular basis, skidding can occur when the coefficient of friction between the tyre and road/runway surface is inadequate to maintain full adhesion. Pavement texture is broken into two components known as Macro and Micro texture.

The macro-texture of a pavement refers to the visible roughness of the pavement surface as a whole. The primary function of the macro-texture is to help maintain adequate skid resistance to aircraft/vehicles travelling at high speeds. It also provides paths for water to escape which helps to prevent wheels of motor vehicles and aircraft hydroplaning. This is normally accomplished through cutting or forming grooves in existing or new pavements (see figure 1).

Micro-textures refer to the roughness of the surface of the pavement. It is the fine texture that occurs on chippings and other exposed parts of the surfacing. For concrete pavement this is usually the sand and fine aggregates present at the surface layer and for asphalt it is usually the type of aggregates used.

Micro-texture creates frictional properties for vehicles and airplanes travelling at low speeds. The wet skidding of a road or taxiway is dependent on the interaction of the tyre and the micro-texture of the road surface.

References will be made to airport pavements, as structural damages are more evident and critical due to the extra precautions that are required and the cost of pavement investments to airports.

The FAA Advisory Circular 150/5320-12C explains the FAA view on Measurement, Construction and Maintenance of Skid-Resistant Airport Pavement surfaces

Pavement Maintenance Tools

• This presentation is not focused on maintenance tools, however a short information seems valuable for future studies.
• Roughness of a pavement can be measured by programs available through FAA or APRas.
• Skid Measurements are recommended by ICAO Annex 14 to be done frequently, using different devices, each having unfortunately their own friction level. A harmonization process of these devices is under way but will still need time.
• Structural conditions of in-service pavements are evaluated using Non-destructive Deflection Testing (NDT).
• Necessary to identify Classification Numbers like Pavement Classification Numbers PCN (understanding pavement performance characteristics) or Aircraft Classification Numbers ACN predicting pavement loading.
• The Pavement condition survey and rating procedures are fully documented in FAA Advisory Circular 150/5380-6 See Marc Stet in Pavement Maintenance Management Tools International Airport Review issue 4 2006.