Date of this Version
Nsengiyumva, G. M., Kim, Y-R., Hu, J. (2020). Feasibility and Implementation of Balanced Mix Design in Nebraska. NDOT Research Report SPR-P1(19) M080.
Balanced mixture design is an alternative asphalt concrete design method that incorporates the performance of mixtures during the design. Balanced mixture design consists of performance test methods and performance criteria. Compared to the existing Superpave design method which mostly relies on volumetrics to design mixtures, balanced mixture design is more suited to account for performance improvements originating from reclaimed asphalt pavement and other foreign additives such as rejuvenators, warm- mix asphalt additives, polymers, and anti-stripping agents. This study investigated the feasibility of the implementation of balanced mixture design in Nebraska mixtures by exploring appropriate test methods (i.e., for fracture and rutting) and method of selection of performance criteria. For the fracture test, the semicircular bend test method was selected and investigated for the appropriate testing conditions that can provide repeatable results. These testing conditions included: the number of replicates, specimen thickness, testing temperature, notch length, and loading rate. Also, the effect of the semicircular bend testing configurations on the test results and their repeatability was explored. For the rutting performance test, a simple rutting test called Gyratory stability was explored by determining critical testing conditions that can aid repeatable results and practical implementation. The validity of the newly developed Gyratory stability test was accomplished by correlating its test results to that of the established flow number test. The correlation showed interchangeability between the Gyratory stability and the flow number, which demonstrated the feasibility of the Gyratory stability as a rutting performance test. Finally, the two performance tests (semicircular bending and Gyratory stability) were conducted for typical Nebraska asphalt concrete mixtures and several additional mixtures including high amounts of recycled materials with rejuvenating agents. Test results were incorporated with a performance space diagram.