ASTM_D_8259_-_D_8259M_-_21.pdf

Designation:D8259/D8259M21Standard Test Method forRotary Wheel Testing(RWT)of Compacted AsphaltMixtures1This standard is issued under the fixed designation D8259/D8259M;the number immediately following the designation indicates theyear of original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of lastreapproval.A superscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method describes a procedure for testing therutting and moisture susceptibility of asphalt specimens usingthe Rotary Wheel Tester(RWT).Superpave Gyratory Compac-tor(SGC)specimens(Test Method D6925)are wrapped,conditioned,submerged in water,and confined between threemetal wheels in continuous synchronized rotation with eachwheel applying a fixed load around the periphery of thespecimen.The system records the number of load cyclesapplied to the specimen,the deformation of the specimen(rutdepth),the loading rate,the temperature of the water,andSigma,which is an indication of specimen roundness.1.2 The test method is used to determine the prematurerutting susceptibility of asphalt mixtures by measuring rutdepth as a function of number of load cycles throughout thetest.1.3 This test method also measures the potential for mois-ture damage effects because the specimens are submerged intemperature-controlled water during preconditioning and forthe duration of the test.1.4 The parameters of the test are shown in Table 1.See anexample of the test parameters used in Appendix X1.NOTE1This test uses a typical specimen produced by a Superpavegyratory compactor.NOTE2The ruggedness study identified air void content as the mostinfluential factor evaluated and recommended a tolerance of 60.25%tominimize the effect of air void content on the test results.The precisionstudy evaluated three asphalt mixtures with specimen air void contentsranging from 2.87%to 3.23%,from 4.28%to 4.64%,and from 5.77%to 6.19%.Precision statements covering the air void content ranges of2.75%to 4.75%and 5.75%to 6.25%can be found in Section 10.Lemke and Bahia(2019)found that an asphalt mixture with 7%air voidcontent was more susceptible to rutting than a mixture with 3%air voidcontent and that the test results for the 7%AV mixture did notdifferentiate between control factors such as test temperature and mixturesource like the mixture with 3%air void content did.NOTE3The University of Wisconsin at Madison Modified AsphaltResearch Center(2017)reported that the City of LA selected the testtemperature of 60 C 140 F because“(1)it approximates the observedhigh average temperature of most pavements,(2)it is close to the hightemperature performance grade classification of the asphalt binder used inmost local applications,(3)it allows a test to be performed in anaccelerated time frame(about 2 h excluding preconditioning time),and(4)research on rut testing has shown that the asphalt binder seems to havethe most control over the test results at lower test temperatures.”Theruggedness study was completed at 60 C 140 F using PG 64-10 with50%RAC asphalt mixture.The precision study was completed at 60 C140 F using PG 64-10 with 50%RAC asphalt mixture for two of themixtures evaluated and using PG 76-22 for the third mixture considered.One may wish to consider lower test temperatures because Lemke andBahia(2019)reported reducing the test temperature from 60 C 140 Fto 52 C 125.6 F when testing PG 58S-28 and PG 58H-28 asphaltbecause of premature failure.Note 8 includes a suggestion for selecting analternative test temperature based on the binder if one chooses to do so.NOTE4The University of Wisconsin at Madison Modified AsphaltResearch Center(2017)reported that the City of LA selected 6900 loadcycles as the maximum load cycles because“initial observations fromtests showed that most samples tested showed their performance wellbefore these values(6900 load cycles and 6.0 mm 0.24 in.)were attained.while those that exhibited low rut depth in the field and no moisturesusceptibility showed test result curves that behaved as asymptotes to theirinitial creep slope until the maximum number of cycles(30 000 cycles)ofthe machine was attained.”6900 load cycles was used in both theruggedness and precision work as well.The machine has an allowablerange of 300 to 30 000 load cycles.NOTE5The University of Wisconsin at Madison Modified AsphaltResearch Center(2017)reported that the City of LA selected 6.0 mm0.24 in.as the maximum rut depth because“initial observations fromtests showed that most samples tested showed their performance wellbefore these values(6900 load cycles and 6.0 mm 0.24 in.)were attained.while those that exhibited low rut depth in the field and no moisturesusceptibility showed test result curves that behaved as asymptotes to theirinitial creep slope until the maximum number of cycles(30 000 cycles)ofthe machine was attained.”6.0 mm 0.24 in.was used in both theruggedness and precision work as we