Pavement Armor

Well the answer lies in the level of protection that each material offers and at what stage in the structural and maintenance life the pavement surface treatments are applied versus the cost for each material.

To effectively compare these two materials and their ability to protect the road, the following performance properties need to be understood:

• Rut resistance
• Wear resistance
• Resistance to Aging
• Fracture Resistance

Rut Resistance. Traditional ultra thin pavement preservation materials are unlikely to rut.  However, in warm climates, the supporting asphalt layers could still be prone to rut.  This means that surface treatments are required to withstand the development of rutting beneath it.  This rutting should be accommodated by both materials if the rutting is as much as 1/8” of an inch up to ¼” of an inch.  It should also be considered that both concrete and chip seal materials could reduce the rutting potential of the supporting layers by reducing the surface temperature due to their higher Solar Reflectivity Values.

Wear resistance of surface treatments is associated with friction loss due to abrasion caused by traffic wear.  The concrete materials are far more likely to offer more resistance than bituminous materials throughout its lifecycle as the product does not experience a change in state when subjected to aging, UV or extreme temperatures.

Resistance to Aging. The aging of materials is likely to cause shrinkage cracking in asphalt materials, whereas in a polymer modified concrete, minimal shrinkage is anticipated without cracking due to the hydration process in the initial life of the material.  In low humidity and high temperature environments, the concrete will show no signs of aging, whereas the bituminous treatments will age rapidly unless other measures are used to retard the aging.

Fracture Resistance. The presence of cracks in the underlying layers is likely to reflect through the new surface treatment whether they are concrete or asphalt.  However, in warmer climates the bituminous materials are more likely to mitigate the crack reflection until it age hardens.  In cold climates, the asphalt will become brittle and the cracks will reflect through due to traffic or environmental induced stresses.  Reflective cracks will reflect through the concrete materials unless additional crack reflection resistance measures are taken.  The advantage of the concrete materials is that they can easily accommodate high tensile low strain Geogrids or Geomats as the concrete and these Geomaterials are strain compatible.

So it would appear that both materials offer performance advantages in different climatic environments.   However, the concrete materials do have the advantage that they are resistant to aging, and have a high wear resistance which means that they have the ability to extend the maintenance design period significantly (10 – 20 years) in comparison to bituminous materials (2 – 8 years) thereby requiring fewer maintenance interventions.  Therefore the life cycle cost benefit should be performed using the initial cost and anticipated maintenance life for each possible intervention.

The author suggests that one considers all of the above when selecting either a Concrete or Bituminous material for your surface treatment.