CAIT project no.: 98 RU6677
Fiscal Year: 2000/2001
Rutgers-CAIT Author(s): Thomas Bennert, Ali Maher
External Author(s): Ivana Marukic, Anthony Chmiel
Sponsor(s): NJDOT, FHWA-USDOT
The research project encompassed developing a testing procedure to accompanying the HMA volumetric design. Currently, there does not exist a simple performance test that addresses whether or not a HMA mix will perform adequately once compacted in the field. Recent efforts through the NCHRP program has proposed a method that could be used, however, the method utilizes sample coring and cutting methods that make the test procedure highly labor intensive. Therefore, it was proposed to develop a testing method that could be conducted immediately after the mix design procedure without the need for extensive sample preparation. The test method to be used also had to have an accepted testing procedure and simulate the rutting mechanisms found in the field.
A rutting criteria is proposed to be used with the Asphalt Pavement Analyzer (APA). The APA is a loaded-wheel test that uses a 100 lb. steel wheel load applied to a 100 psi pressurized hose that lays overtop of the asphalt samples. The samples are easily compacted to a required 77mm tall and air void content of 7% using the gyratory compactor, with no need to cutting or coring. The samples are heated to a temperature of 64oC for fours hours prior to testing. After this conditioning stage is complete, the steel wheels then run back and forth over the samples for a total of 8,000 loading cycles. The total rutting that occurs after the 8,000 loading cycles is then used in the proposed pass/fail criteria.
The criteria was developed by testing eleven different mix designs. Six designed for very heavy traffic, four designed for heavy traffic and one designed for medium to low traffic. Both coarse and fine gradations were used, as well a three different PG binder grades; PG64-22, PG70-22, and PG76-22. The results of the testing allowed for the construction of the criteria based on the design gyration number. The rutting criteria was verified in the laboratory by using the NY/NJ Port Authority’s Heavy Volume Mixes (HVM), as well as other industry mixes. However, as to this date, field verification has not been conducted.