This IDEA Type 2 research project validated a field prototype of the Duomorph Asphalt Rheology Tester (DART), a portable liquid binder testing device that is inexpensive, simple to use, and quick to check binder consistency in production plants and field laboratories. The DART technology, which has evolved over multiple research projects, was verified under controlled laboratory experiments in the past. The current study focused on developing a field-ready prototype and validating the effectiveness of DART to identify noncompliant binders in the field using samples from real-world construction projects. The research team also used the DART in a production facility to assess its applicability in optimizing binder production operations.
Previous studies established a preliminary test protocol to fingerprint binder samples. The procedure involves recording the DART response in the binder sample at temperatures from 150°F to 70°F, and at frequencies from 0.5 to 100 Hz, to generate a material-specific fingerprint. The fingerprint uses the response of the DART in the binder sample relative to its response in air and utilizes data filtered based on preset criteria for signal noise tolerance and physical relevance of the magnitude of response. The fingerprint of a certified binder (or an approved binder) is compared against the fingerprints generated for field samples to determine the consistency of the binder used in the project. A lack of consistency is determined based on statistical parameters established under the DART research studies. This IDEA Type 2 project bridges the gap between research and application by providing the necessary field validation to support agency implementation.
This study validated that the DART can match binders of a similar PG grade and distinguish between different grades. Next, in tests using unaged samples from construction projects in two States, one in the Southeast and one in the Midwest, samples failing to comply with the AASHTO M 320 specification could be identified based on fingerprint comparisons of samples that satisfied the specification requirements. These tests covered samples from multiple days of paving and across a range of binder types, PG 68-22, 64-22, 67-22 and 76-22. Further, tests on samples from an asphalt binder production facility showed that the trends in viscosity were evident and there is potential for use of the DART in a binder optimization process. Extensive testing and validation will be required to establish a procedure for this application, however.
Based on the results of this study, the DART device is proposed as an effective tool for process control of asphalt binders to enable larger sampling rates and faster testing of asphalt binders in production facilities or district laboratories. Testing can be completed in as few as 2.5 hours with minimal operator time or skills, which is a significant advantage over the conventional AASHTO M 320 procedure. In its current stage of development, the DART can supplement, although not replace, AASHTO M 320 PG specification testing. It provides a means to verify binder consistency or to check deviation of a field sample from a certified sample.
The implementation of the DART device offers several benefits including (a) simple and quick testing to detect deficient quality, (b) reduced risk of premature pavement failures for owners and the traveling public, (c) lowered risk of accepting inferior materials for owners, (d) lowered risk of litigation between suppliers, contractors, and owners, (e) cost savings for suppliers and owners resulting from higher sampling rates when using DART as a screening device, and (f) generation of data previously unavailable to advance the understanding of binder science.
The final report is available.
