Development and Validation of a Nondestructive Methodology to Measure Subgrade Moisture Contents at the NCAT Pavement Test Track

Abstract

The Pavement Test Track is a full-scale, accelerated performance test (APT) facility for flexible pavements managed by the National Center for Asphalt Technology (NCAT) at Auburn University. Forty-six unique 200-foot test sections are installed around a 1.7-mile oval and subjected to accelerated damage via a fleet of tractors pulling heavy triple trailers in order to compress 10 million equivalent single axle loadings (ESALs) of pavement damage into 2 years of fleet operations. Methods and materials that produce better performance for research sponsors are identified so that future pavements can be constructed based on objective life cycle comparisons. Test sections are built on the NCAT Pavement Test Track with a focus on surface mixes, structural pavement design, or pavement preservation. Off-Track test sections with a focus on pavement preservation were built in the summer of 2012 on a nearby low volume roadway where electronic instrumentation was impractical; however, changing subgrade moisture content was needed in both treated and untreated test sections in order to fully document the benefit of pavement preservation. A nondestructive methodology was developed in order to quantify changing subgrade moisture content without using imbedded sensors. An overview of the measurement methodology and observed relationships between cracking and subgrade moisture content measurements are summarized in this document.