NCHRP Project 9-43: Mix Design Practices for Warm Mix Asphalt
Client: National Cooperative Highway Research Program
AAT completed this national research and development project on warm mix asphalt in 2011. The primary product of this project was a proposed appendix to AASHTO R35 entitled Special Mixture Design Considerations and Methods for Warm Mix Asphalt (WMA). A commentary for the appendix and training materials were also prepared. The proposed appendix was published in the 2012 edition of the AASHTO Standard Specifications for Transportation Materials and Methods of Sampling and Testing.
Asphalt Acceptance Testing, Maryland 200 Contract B
Client: Greenman-Pedersen, Inc.
In 2011, AAT performed acceptance testing for approximately 400,000 tons of hot mix asphalt concrete placed during Contract B of the Intercounty Connector. Standard mixture volumetric testing was conducted with a turn-around time of 24 hours.
Stone Matrix Asphalt Specification and Implementation
AAT completed this project for the Pennsylvania Department of Transportation in 2010. The project included the development of a specification for Stone Matrix Asphalt and training to support the implementation of the specification. A total of 6 training sessions were presented throughout Pennsylvania to introduce the specification to engineers and technicians.
WHRP PRoject 0092-10-06: Effect of Recovered Binders From Recycled Shingles and Increased RAP Percentages on Resultant Performance Grade
AAT completed this research and development project for the Wisconsin Highway Research Program in 2011. This research evaluated the properties of recycled asphalt binders from Wisconsin sources. Continuous grading properties were measured for 18 recycled binder sources: 12 reclaimed asphalt pavement (RAP) sources and 6 recycled asphalt shingle sources (RAS). The data were used to evaluate the binder replacement criteria contained in the 2011 Wisconsin Department of Transportation (WisDOT) Standard Specifications for Highway and Structure Construction using a reliability analysis. Recommendations were made to improve the reliability of the low temperature grade of the binder in the mixtures when recycled sources are used.
Evaluation of Raveling in the 2002 Rehabilitation of Niagara Falls International Airport Runway 10L-28R
Client: URS Corporation
In this project AAT performed testing and analysis to identify the cause of raveling that occurred in the 2002 rehabilitation of Niagara Falls International Airport Runway 10L-28R. The analysis was completed in 2006, approximately 4 years after the overlay was placed. The scope of this investigation included sampling and testing of asphalt concrete cores from the pavement, a review of available documentation from the project, and analysis of the resulting data. This forensic investigation concluded that the early raveling that occurred was primarily the result of low effective binder content at specific locations in the top lift of the mixture. These localized areas of low effective binder content appear to have been caused by the combined effects of segregation and a low design effective binder content. The findings from this investigation also lead to the conclusion that raveling of additional areas of the pavement should be expected with time. It was recommended that the overlay be removed and replaced.