This study presents laboratory evaluation integrated with field performance to examine two widely used warm-mix asphalt (WMA) approaches-foaming and emulsion technology. For a more realistic evaluation of the WMA approaches, trial pavement sections of the WMA mixtures and their counterpart hot-mix asphalt (HMA) mixtures were implemented in Antelope County, Nebraska. Fieldmixed loose mixtures collected at the time of paving were transported to the laboratories to conduct various experimental evaluations of the individual mixtures. Among the laboratory tests, three (two conventional and one newly attempted) were performed to characterize moisture damage potential which is the primary focus of this study. From the laboratory test results, WMA mixtures showed greater susceptibility to moisture conditioning than the HMA mixtures, and this trend was identical from multiple moisture damage parameters including the strength ratio and the critical fracture energy ratio. Early-stage field performance data collected for three years after placement presented satisfactory rutting-cracking performance from both the WMA and HMA sections, which generally agrees with laboratory evaluations. Although the field performance data indicated that both the WMA and HMA show similar good performance, careful observation of field performance over aperiod of years is necessary since moisture damage can be accelerated after rutting or cracking as a later-stage pavement distress.
Cracking in asphaltic pavement layers causes primary failure of the roadway structure, and the fracture resistance and characteristics of asphalt mixtures significantly influence the service life of asphaltic roadways. A better understanding of the fracture process is considered a necessary step to the proper development of design-analysis procedures for asphaltic mixtures and pavement structures. However, such effort involves many challenges because of the complex nature of asphaltic materials. In this study, experiments were conducted using uniaxial compressive specimens to characterize the linear viscoelastic properties and semi-circular bending (SCB) specimens to characterize fracture behavior of a typical dense-graded asphalt paving mixture subjected to various loading rates and at different temperatures. The SCB fracture test was also incorporated with a digital image correlation (DIC) system and finite-element model simulations including material viscoelasticity and cohesive-zone fracture to effectively capture local fracture processes and resulting fracture properties. The test results and model simulations clearly demonstrate that: (1) the rate-and temperature-dependent fracture characteristics need to be identified at the local fracture process zone, and (2) the rate-and temperature-dependent fracture properties are necessary in the structural design of asphaltic pavements with which a wide range of strain rates and service temperatures is usually associated.
It is important to determine the mechanical properties of rock materials accurately from the viewpoint of the design, analysis, and modeling of various transportation infrastructure systems. Conventional methods have some drawbacks, including relatively inaccurate measurements, cumbersome testing-analysis processes, and high variability in measurements. A nanoindentation test integrated with a numerical modeling technique has been validated in other fields as an efficient and accurate tool for the characterization of the key mechanical properties of various irregularly shaped materials, such as the rock materials in this study. This paper presents an integrated experimental-numerical effort based on the nanoindentation measurement and finite-element modeling of a representative rock material, limestone. The experimental efforts, including specimen fabrication and laboratory tests, are presented, and the corresponding analyses of test results combined with the finite-element technique and linear interpolation to evaluate the property measurements are discussed. The elastic properties estimated from the nanoindentation test are similar to the simulation results, demonstrating the validity of the test method and modeling approach.The success of the proposed approach should facilitate the better design of mixtures and structures based on the more accurate characterization of the core material properties.
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