Density Observations from a Full-Scale, Untrafficked Test Section with Guidance for Dryback Methods

• Published in: Transportation research record 2017, Vol.2630 (1), p.134-146
• Main Authors: Smith, Braden T., Moore, Robert A., Howard, Isaac L.
• Format: Article
• Language: English
• ISSN: 0361-1981; 2169-4052
• DOI: 10.3141/2630-17

This paper presents a discussion with data on factors related to the in-place density measurement of asphalt pavements. A review of the literature traces changes to asphalt density measurement technologies over the past 60 years. Two phases of investigation then are presented in which in-place density was evaluated for an ongoing study of environmental effects at a test section in Columbus, Mississippi. A series of laboratory and field activities was performed in Phase 1. In Phase 2, studies were made of laboratory drying practices of specimens that were cored after an extended period of field aging. The key conclusion from these efforts was that ASTM D7227 might not remove sufficient moisture from some specimens to achieve accurate density measurement when pavements have been exposed to moisture for extended periods of time. This paper presents a case with an average error in air void measurement of 0.9% (measured 9.1% when 10% was correct) for specimens that were cored, dried according to ASTM D7227, and then measured for mass in air 1 day later. This finding is of most concern to rehabilitation and research work in areas in which aggregates have high potential for absorption but is of no concern to new construction projects. Furthermore, the work presented here validated the use of ASTM D7227 in circumstances in which mixtures were exposed to moisture for short periods of time. The work also suggested three options to take to accurately measure in-place density for performance testing of aged pavements that contain high-absorption aggregates (i.e., dry in oven, develop correlation equations, or dry for several weeks).