Comparison of 9.5 mm SuperPave and Marshall Wearing I Mixes in ...

43CHAPTER 5 MIX DESIGN, SAMPLE PREPARATION AND APA TESTING5.1 MARSHALL MIX DESIGNTo ensure the research results are applicable to local conditions, mixes evaluated during theresearch used locally available materials and were proportioned in accordance with WVDOHprocedures and specifications, as presented in Table 2.2. Mix designs were prepared for boththe medium and heavy traffic levels.5.1.1 Type of Mixes DevelopedFour Marshall mix designs were needed for this research, the combinations were:Traffic Aggregate DesignationHeavy 100% limestone M HVY 100%LSMedium 100% limestone M MED 100%LSHeavy Maximum allowable natural sand M HVY 13%NSMedium Maximum allowable natural sand M MED 13%NSThe WVDOH design practice is to use the medium traffic level for the Marshall mix designs whenthe design traffic is less than 3 x 10 6 ESALs. Thus, the medium traffic level design is used for lowvolume roads.Mix designs prepared by J. F. Allen were used for the heavy and medium traffic level designswith 100% limestone aggregate. Specific design criteria values, percentages and aggregateproperties for all developed mix designs are presented in the Appendix C. These designs wereconfirmed by making samples containing the design aggregate blend and optimum asphaltcontent indicated in the J. F. Allen mix design. These samples were checked for stability, flowand volumetric parameters.The second set of Marshall designs was developed to contain the maximum amount of naturalsand as permitted by volumetric requirements. These Marshall mixes were designed inconjunction with the Superpave designs containing a maximum amount of natural sand. It wasdiscovered that the same gradation was acceptable and optimal for both Marshall andSuperpave.5.1.2 Aggregate Preparation and Gradation DevelopmentBefore any mixes could be developed, the aggregate acquired from both sources needed to besieved into proper aggregate size classifications and cleaned. Aggregate was sieved into 3/8”,#4, #8, #16, #30, #50, #200 and Pan sizes. Sieving was accomplished by using a Mary Ann