NCHRP IDEA 20-30/IDEA 170 [Completed (IDEA)]
Development and Implementation of the Asphalt Embrittlement Analyzer
[ NCHRP 20-30 (NCHRP-IDEA) ]
| Project Data
||University of Illinois|
||William G. Buttlar|
The objective of this project was to develop, demonstrate, and implement an innovative acoustic emission-based “Asphalt Embrittlement Analyzer” (AEA) system for rapid and reliable characterization of embrittlement temperatures (TEMB) of asphalt binders and asphalt mixtures. Work in the initial stage focused on extending the acoustic emission (AE) technique to extract discrete and continuous low temperature cracking characterization (i.e., embrittlement temperature) of asphalt material from age-graded asphalt concrete such as field cores. Work in the final stage concentrated on obtaining a smooth and continuous embrittlement temperature profile from a field core specimen using an innovative, multi-sensor approach. The cooling chamber of the AEA system has been retrofitted by the commercial partner, Troxler Electronic Laboratories, to allow closed-loop, linear cooling. Theoretical and experimental studies were conducted to determine the best core geometry and sensor placement. Reliable and user-friendly computer software with an interactive user interface was developed for source location with the capability to locate AE sources within an 1/8 inch resolution or better. The developed AEA software analyzes AE signals and automatically generates color-coded continuous embrittlement temperature profiles versus depth from surface for the field core along with rehabilitation recommendations (guided by an expert system). Asphalt concrete cores obtained from the field that exhibit visible signs of distress were successfully tested. Working in collaboration with industrial partners (Troxler, Road Science, and Asphalt Institute), a temperature-controlled device coupled with multi-channel AE and software was completed to calculate TEMB vs. depth and a prototype AEA system for commercialization was designed. Finally, a series of maintenance strategies and an expert system to guide designers toward an optimally designed rehabilitation strategy was developed. The prototype AEA device, now capable of measuring graded in situ embrittlement characteristics, is ready for final commercialization. This will likely involve field validation across a broad range of materials and climates across the United States, vetting through the FHWA mixtures expert task group (ETG), development of an AASHTO test standard, round robin testing, and finalization of commercial equipment-based data and experience from these subsequent efforts.