RELATIONSHIP OF SUPERPAVE GYRATORY COMPACTION PROPERTIES TO HMA RUTTING BEHAVIOR
This report presents the findings of a research project to examine whether there is a relationship between any property of hot mix asphalt (HMA) measurable with the Superpave gyratory compactor and the rutting behavior of HMA pavements in service. Its main finding is that the parameter N-SRmax, the number of gyrations at maximum stress ratio, may be used within certain limits to identify mix designs likely to show gross instability under the shear stresses produced by traffic in HMA pavements. The report will be of particular interest to materials engineers in state highway agencies, as well as to materials suppliers and paving contractor personnel responsible for HMA design and quality control.
Permanent Deformation Evaluation of Idaho Superpave Mixes Using the Gyratory Stability
With the full implementation of Superpave mix design in the State of Idaho, a performance parameter, referred to as the Gyratory Stability, has been developed. It is calculated from the accumulated shear energy in the mix during compaction. Results of the Gyratory Stability (GS) of thirteen tested mixes from the lab and field compared well with various performance indicators. Performance evaluation of these mixes was conducted using Asphalt Pavement Analyzer (APA), Dynamic Modulus (E*) and the Flow Number (FN). The GS results showed good correlation with rut-depth measured in APA and with E*, phase angle and the FN parameters measured in the Superpave Performance Tester (SPT). The results also showed that GS was more sensitive to the changes in mix design parameters. Overall, the results indicate that GS has the potential to be used as a screening tool for Hot- Mix Asphalt design and as a quality control indicator onsite.
VERIFICATION AND APPLICATION OF THE VESYS STRUCTURAL SUBSYSTEM --PROCEEDINGS OF THE FIFTH INTERNATIONAL CONFERENCE ON THE STRUCTURAL DESIGN OF ASPHALT PAVEMENTS HELD DEFLT UNIVERSITY OF TECHNOLOGY, AUGUST 23-26 1982. VOL 1 AND 2. -- NETHERLANDS
At the fourth international conference, the general modular framework of the vesys structural subsystem was presented. Since then, major improvements to the models were made. These improvements allow for the input of variation in material properties with seasonal environmental changes, discrete axle load groups, up to eight layers, prediction of fatigue in any layer, low temperature cracking damage and the permanent deformation occurring in each layer. One of three optional modes of the primary response model uses the principle of quasi elasticity to compute time step solutions to the chevron n-layer elastic theory bvp, resulting in the time varying response at any point in the pavement due to a stationary load applied to the pavement's surface. This response is treated in a similar manner as in vesys-iim through boltzman's superposition principle to calculate the pavement's viscoelastic response when the load is moving across the pavement's surface at any speed. A second option allows for input of a single modulus for each layer and season, and the elastic layer theory bvp calculates a single time-independent response. A third optional mode computes the layer moduli indirectly from the layer creep curves. The terms "viscoelastic-plastic" and direct and indirect "elastic-plastic" are used to distinguish between the three different options available. A comprehensive study of the predicted versus measured behaviors of selected AASHT road test sections is made using the new vesys subsystem. In addition, the results of two in-house research studies conducted at FHWA are summarized as examples of the use of vesys in a research capacity. One of these is an effort to evaluate the potential of "sulphlex" paving mixtures in light of the recent energy crisis. Another is that dealing with the development of load equivalencies which realistically represent load induced distress in various environments. The use of these functions are a critical component in studies dealing with life cycle costing analyses such as cost allocation and selection of optimum maintenance strategies.(a) for the covering abstract of the conference see IRRD 815640.