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This study evaluates hydrated lime-treated hot-mix asphalt (HMA) mixtures through various laboratory tests, including the dynamic modulus test and performance tests to characterize permanent deformation and fatigue damage resistance both in displacement-controlled and force-controlled modes. Two different asphalt mixtures-the asphalt concrete mixture and the fine aggregate asphalt matrix mixture-which differ only in the amount of additional hydrated lime (0.5-3.0%), are tested. Test results demonstrate material-specific damage characteristics of hydrated lime and the existence of a more appropriate amount of hydrated lime to be added to the HMA mixtures than the current typical application rate such as the addition of 1.0% lime to dry or premoistened aggregates. In addition, the newly released Mechanistic-Empirical Pavement Design Guide (MEPDG) is used for predicting pavement performance related to hydrated lime content. The MEPDG analysis results show ( 2 0 1 0 ) 2 that damage prediction models implemented in the current MEPDG are limited to accurately predicting material-specific damage characteristics. Mechanistic models that consider material-specific crack phenomenon and fracture behavior should be pursued. , C O N S T R U C T I O N A N D B U I L D I N G M A T E R I A L S 24

Dynamic modulus is the key property used to characterize stiffness of asphaltic mixtures in pavement performance evaluation programs such as the Guide for Mechanistic–Empirical Design of New and Rehabilitated Pavement Structures. This paper investigates various models for predicting the dynamic modulus of asphalt mixtures and compares model predictions with experimental test results. The predictions of two semi-empirical models (Witczak's model, modified Hirsch model), an analytical micromechanics model (Hashin's model), and the computational micromechanics model are compared with the dynamic modulus test results obtained from cylindrical asphalt concrete specimens. For the computational micromechanics approach, the finite element method was incorporated with laboratory tests that characterize the properties of individual mixture constituents and with a digital image analysis technique to represent detailed microstructure characteristics of asphalt concrete mixtures. All predicting models investigated in this paper are in fair agreement with the test results. Witczak's equation simulates dynamic moduli somewhat greater than laboratory test results, whereas the modified Hirsch model generally underpredicts moduli. The computational micromechanics model presents a relatively higher deviation at lower loading frequencies, but it shows better predictions because the loading frequency is higher. Hashin's analytical micromechanics model is limited to accurately predicting the dynamic modulus of the asphalt mixtures because of geometric simplifications and assumptions. With further improvements, the computational micromechanics method incorporated with the testing protocol seems attractive, because it can directly account for geometric complexity due to aggregates and inelastic mixture component properties with fewer of the required laboratory tests.

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Fracture damage mechanisms are some of the most significant causes of structural failure in asphalt mixtures. Ye t much research is still needed to understand properly the fracture process in such complex materials. The study reported in this paper investigated several experimental testing protocols available in the literature to characterize fracture properties of asphalt mixtures. Two bending tests (i.e., semicircular bending, single-edge notched beam) and one tension test (disk-shaped compact tension) were performed. An integrated approach that combined experimental tests and numerical simulations was applied to characterize fracture properties of a fine aggregate mixture. The experimental tests were simulated with a computational model on the basis of the finite element method, which was incorporated with material viscoelasticity and cohesive zone fracture. Two cohesive zone fracture parameters (i.e., cohesive strength, fracture energy) were determined through a calibration process until a good match between experimental and numerical results was observed. To illustrate the efficiency of the integrated numerical–experimental approach, fracture properties also were determined through a traditional methodology that used globally averaged material displacements far from the actual fracture process zone. The results indicated that different fracture properties at low temperatures might be obtained from simulations of a single test, regardless of the sample geometry or loading configuration. Through further testing and analysis, it is expected that the modeling approach employed in this work can provide meaningful insights into the effects of constituents on an overall mixture's performance, with significant savings in experimental cost and time.