The significance of the NaturalPAVE® XL Resin Pavement™ technology is clear when the environmental advantages are considered in: no air pollution or fossil fuel burning required to heat the product during its manufacturing, transportation or placement; and no toxic petroleum components to contaminate land and water. These pavements retain the natural coloration and texture of the constituent aggregate materials. Additionally, these light colored solar reflective pavements provide a cool alternative to black asphalt and its deleterious contributions to the Urban Heat Island Effect, smog formation, greenhouse gas emission, global warming and climate change

Public interest in environmentally responsible design and construction continues to motivate increased awareness and implementation of green construction technology. The U.S. Green Building Council (USGBC) and its LEED program (Leadership in Energy & Environmental Design), a Green Building Rating System, has provided a vitally important standard format for agency personnel and design consultants who specify the materials for new construction and remodeling projects. Many facilities are now being constructed according to these standards. The LEED rating system has set the bar high and NaturalPAVE XL Resin Pavement is ideally suited for green building pavement requirements.

NaturalPAVE materials are classified as flexible pavements, similar to Hot Mix Asphalt, and like asphalt they are installed by asphalt paving machines in continuous joint-free layers.  This is in contrast to Portland Cement Concrete pavement, which is classified as rigid pavement and requires the use of expansion joints to control shrinkage cracking. 

A series of tests was conducted by an asphalt pavement materials testing laboratory for the evaluation of a NaturalPAVE XL Resin Pavement mixture in comparison to conventional hot mix asphalt. The NaturalPAVE XL Resin Pavement material, which is non-toxic, cold-manufactured and cold-applied, and typically solar reflective as an installed product, outperformed conventional Hot Mix Asphalt pavement based on Resilient Modulus testing. Resilient Modulus testing is the method standardized by the U.S. Department of Transportation’s Federal Highway Administration (FHWA) for the evaluation of pavement materials performance and recognized both nationally and internationally.  In the interest of replicating the dynamic loading conditions that pavement layers experience under constant automobile and truck traffic, Resilient Modulus testing evaluates the elasticity of the pavement material and its ability to be resilient and return to its original shape and size without any permanent deformation, or damage, after repetitive loading cycles are applied.

The test results indicated that at 77°F (25°) temperatures, a one inch (25 mm) thick layer of NaturalPAVE is equivalent to approximately two inches (50 mm) of Hot Mix Asphalt.  Averaging the Resilient Modulus test values at the 120°F (49°C) temperature, a one inch (25 mm) thick layer of NaturalPAVE was equivalent to more than four inches (100 mm) of Hot Mix Asphalt pavement. Taking all the testing data into account, a layer of NaturalPAVE XL Resin Pavement would be equivalent to a Hot Mix Asphalt pavement material of approximately twice the layer thickness.  In hotter climates, the results of both Marshall Stability and Resilient Modulus testing indicate that more than twice the amount of Hot Mix Asphalt would be required in order to be equal to a thinner layer of NaturalPAVE XL Resin Pavement.

The most important aspect of a cool pavement is its ability to reflect rather than absorb solar energy. Among the traditional pavement materials, concrete sets the standard as being the most reflective (high albedo), while black asphalt is the least reflective (low albedo) and most absorbent of solar energy. Typically NaturalPAVE XL Resin Pavement mixtures are formulated with light colored aggregate mixtures and consequently have high solar reflectance similar to concrete pavements. The differences in pavement surface temperatures between heat absorbent asphalt and highly reflective NaturalPAVE XL Resin Pavement can be significant. For example, utilizing an infrared thermometer during mid-August afternoon conditions (98°F air temperatures) and measuring areas of pavement subject to full day sun exposure, the following pavement surface temperatures were recorded at the zoo facility in Washington, D.C.

As part of its educational mission regarding sustainable living practices for the Las Vegas Valley, the Springs Preserve in Las Vegas, Nevada, has an outdoor exhibit displaying the difference in residual heat between objects that reflect solar energy and objects that are non-reflective and absorb solar energy. Using the lizard thermometer sculptures pictured at right, visitors can observe the temperature differences throughout the day between the reflective white lizard and the heat absorbent black lizard. The 119.4°F and 153.5°F temperatures displayed were recorded mid-morning on a summer day while the air temperatures were still under 100°F. They closely parallel the actual temperatures of reflective NaturalPAVE XL® Resin Pavement and heat absorbent black asphalt pavement surfaces in these same weather conditions, showing that NaturalPAVE XL Resin Pavement is the ideal surfacing for overlaying existing asphalt as well as new pavement installations.

The NaturalPAVE® XL Resin Pavement™ specimens pictured below have solar reflectance measurements that help in meeting or exceeding the minimum Solar Reflectance Index (SRI) of 29 to qualify as high albedo pavement materials. Use of such pavement materials reduces heat absorption and radiance as required for a LEED™ Rating System Point toward “Green Building” Certification from the USGBC as per Credit SS 7.1 (Heat Island Effect) for light-colored/high albedo pavement.

43.5	54.0	39.6	48.8
33.1	52.7	35.7	55.4

Whether it’s air or water quality protection, the comfort of a cool pavement surfacing, or a matter of simple natural aesthetics, NaturalPAVE® XL Resin Pavement™ can be utilized to cover up existing asphalt pavement as an “overlay” in similar manner as additional layers of asphalt are placed on top of older asphalt pavements. As the environmental and aesthetic rationale for overlaying asphalt with a more appropriate pavement surfacing gains further recognition, the tried and proven NaturalPAVE XL Resin Pavement technology will be the obvious choice.

Pictured above is paving work in progress at a recent project in Washington, D.C. The surface of the existing asphalt pavement was milled down so that road surface grades could be maintained once the NaturalPAVE XL Resin Pavement overlay was installed. The NaturalPAVE XL Resin Pavement mixture was placed with a standard asphalt paving machine and asphalt compaction equipment.