The flow number test has also recently been used more often to characterize the rutting resistance of asphalt mixtures. Mohammad et al. evaluated the flow number test using the hot-mix asphalt mix- tures in the state of Louisiana (12, 13). Biligiri et al. evaluated several mathematical models for their abilities to calculate the F N parameter for asphalt mixtures and recommended a new comprehensive model for the accurate determination of F N (14). With the upcoming implementation of the SPTs and the AASHTO M-E design guide at the state level, more efforts on the use of SPTs to characterize the behavior of asphalt mixtures are expected to be made. This paper presents the findings of a study conducted at the University of Tennessee to investigate the simple performance characteristics of plant-produced asphalt mixtures. OBJECTIVES AND SCOPE The primary objective of this study was to evaluate the simple perfor- mance characteristics (| E*| and F N ) of the asphalt mixtures used in the state of Tennessee. The results from the asphalt pavement analyzer (APA) test were also included in the study for comparison with the results of the dynamic modulus and flow number tests. DESCRIPTION OF EXPERIMENT Materials A total of 11 asphalt mixtures were used in this study (Table 1). All the mixtures were plant-produced field mixes from an array of loca- tions within the state of Tennessee. The mixtures were collected from dump trucks in asphalt plants and transported to the University of Tennessee for testing. Once they were acquired, the mixtures were allowed to be reheated only once for specimen compaction to avoid stiffening of the mixture. All mixtures met Tennessee Department of Transportation (TDOT) specifications for 411-D surface mixtures or 307 BM-2 for binder or base mixtures (15). Three coarse aggregate types were used for evaluation of the sur- face mixes: limestone, gravel, and granite with a nominal maximum aggregate size (NMAS) of 12.5 mm for all mixtures. The coarse aggregate angularity was 100%. The fine aggregate used in the surface mixes consisted of natural sand and No. 10 screenings (92% pass- ing a 4.75-mm sieve). Only the gravel mixtures contained recycled asphalt pavement (RAP). Three types of asphalt cement were used in the surface mixtures: PG 64-22, PG 70-22, and PG 76-22. The asphalt contents of all lime- stone mixtures and granite mixture were verified to be approximately Investigation of Simple Performance Characteristics of Plant-Produced Asphalt Mixtures in Tennessee Baoshan Huang, Xiang Shu, and James Bass 140 With the recent adoption of the dynamic modulus, flow number, and flow time tests as simple performance tests (SPTs) to complement the Super- pave ® volumetric mixture design and the selection of dynamic modulus as a basic material property input in the new AASHTO 2002 M-E design guide, SPTs have been receiving more attention and have been more often used in the asphalt community. This paper presents the results from a laboratory study with the asphalt mixtures used in Tennessee obtained by SPTs. Eleven plant-produced mixtures with asphalt cements with different PGs and different aggregates were evaluated by the dynamic modulus and flow number tests. The asphalt pavement analyzer (APA) test was also included in this study to characterize the rutting resistance of asphalt mixtures. The results indicated that generally repeatable data can be obtained from the dynamic modulus test. The flow number test was able to identify the effects of both asphalt cement and aggregate in the rutting resistance of mixtures. The SPTs and APA test produced consistent results in this study. With the recent adoption of the dynamic modulus, flow number (F N ), and flow time tests as simple performance tests (SPTs) as comple- ments to the Superpave ® volumetric mixture design method to ensure the satisfactory performance of designed asphalt pavements, SPTs have been getting more and more attention in the asphalt technology industry and research community (1, 2). The dynamic modulus (| E*|) is one of the fundamental engineer- ing properties widely used to characterize the viscoelastic behavior of asphalt mixtures (3) and has also been selected as a basic material property input in the new AASHTO mechanistic–empirical (M-E) design guide (4). The AASHTO M-E design guide either requires direct laboratory testing for the | E*| value or recommends the use of the Witczak model to predict the | E*| value (5). For laboratory test- ing, many researchers examined the effects of the sample prepara- tion method, strain level, testing protocol, and testing history on the | E*| values of asphalt mixtures (6–8). Many other researchers eval- uated the predictive capability of the Witczak model for the estima- tion of | E*| values by comparing the predicted and measured | E*| values obtained for various mixtures across the United States (9, 10). The Witczak model was also refined and revised to provide better prediction results (11). 223 Perkins Hall, Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, TN 37996. Corresponding author: B. Huang, bhuang@ utk.edu. Transportation Research Record: Journal of the Transportation Research Board, No. 2057, Transportation Research Board of the National Academies, Washington, D.C., 2008, pp. 140–148. DOI: 10.3141/2057-17