Structural Study of Cold Central Plant Recycling Sections at the National Center for Asphalt Technology (NCAT) Test Track: Phase II

About the report:

The Virginia Department of Transportation (VDOT) contracted with the National Center for Asphalt Technology (NCAT) in 2012 to install, instrument, and monitor three pavement test sections at the NCAT Test Track.  These sections were subjected to approximately 20 million 18-kip equivalent single axle loads between 2012 and 2017.  Pavement instrumentation was included in each test section to capture the temperature and pavement response from truck loading.  The three test sections, having a length of 200 ft each, included two different asphalt overlay thicknesses placed on top of a 5-in cold central plant recycled base.  One of the three sections also contained a cement-stabilized base designed to simulate a full-depth reclaimed layer.

The purpose of this study was to conduct a second round of testing during the 2015-2017 research cycle and to evaluate the performance of the three test sections constructed using cold central plant recycling (CCPR) material.  This study follows an earlier effort performed during the 2012-2014 research cycle. The performance of the sections was documented by analyzing the results of deflection testing using a falling weight deflectometer; temperature, pressure, and strain measurements from embedded instruments; and observable surface deterioration of the pavement sections.

The study found that the performance of the three recycled sections continues to be excellent after 20 million equivalent single axle loads of traffic loading.  This was evidenced by the following examples of functional performance: no observable cracking at the pavement surface, rut depths less than 0.3 in, and steady measurements of ride quality.  The claim of excellent performance is also supported by the following examples of structural performance: steady or increasing modulus values for the asphalt/CCPR layer and steady or slightly increasing tensile strain at the bottom of the CCPR layer, vertical base pressure, and vertical subgrade pressure. 

The study recommends that VDOT continue to sponsor trafficking of two of the recycled sections for the 2018 track cycle and further recommends that VDOT find ways to identify and fund additional projects to implement the pavement recycling concepts on in-service pavements in Virginia. 

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