Research Areas of Interets

• Characterization and Modeling of Pavement Materials: Characterization and modeling of asphalt binder, mixture, and asphalt concrete has been my major activity in the last decade. I work on two major issues: MOISTURE DAMAGE - Moisture damage in asphalt has been studied for over 70 years but it still remains an unsolved problem. That is because previous studies did not involve fundamental study of bond damage at the nanoscale level to support characterization and modeling of asphalt concrete for structural integrity at higher scales. My research work quantifies moisture interactions with asphalt-aggregate bonds at the nanoscale level, and relate those interactions to the moisture-induced damage at the macroscale level through nano-macro scales testing, neural network quantification, and unified constitutive model development within the finite element modeling framework. ASPHALT AGING - Asphalt aging affects binder and mixtures mechanical properties such as stiffness, hardness, and viscosity. Understanding how and what structural modifications affect the asphalt binder and mixtures mechanical properties have remained unexplored, largely because these modifications occur at the atomic to molecular scales. My work invloves in fundamental study of integrated nano- and molecular characterization and modeling of asphalt binder to understand the link between asphalt molecular structure and mechanical behavior. Nanoscale testing includes nanoindentation, scanning electron and atomic force microscopy, while molecular modeling includes mathematical and molecular dynamic simulations.


• Mechanistic Design of Pavements: Pavement design has made a paradigm shift by moving a step from traditional empirically based design to mechanics based design called Mechanistic Empirical Pavement Design Guide (MEPDG). MEPDG is expected to better predicts pavement performance through better utilization of local materials, factors such as present-day traffic conditions and regional climate instead of the traditional empirical design methods. However, implementation of the MEPDG at a particular region such as in the state of New Mexico requires the development of design input parameters representing New Mexico pavements, and the determination of the distress model coefficients (also known as local calibration coefficients) and failure criteria for the state specific pavement conditions. Most of my current research projects with the New Mexico Department of Transportation are related to implementation of MEPDG in New Mexico. In addition to MEPDG, I am interested in reliability concept in pavement design, sensitivity of pavement design inputs, inverted and perpetual pavement design alternatives.


• Geomechanics and Transportation Geotechnics: Performance of a pavement system not only depends on the pavement structural layers but also on underlying geomaterials and foundations. My previous research focused on geomechanics of pavement base, subbase, subgrade, and foundation soils for roadway and airfield pavements. I am interested in characterization and modeling of non-traditional materials, polymeric composites, pavement drainage and permeability issues, and unbound aggregates. One of my on- going NSF funded research projects is examining earth dam vulnerability to seepage, deformation, and stability failures under blast loading. I am interested in falling weight deflection testing of airfield pavements and back-calculation by hybrid FEM-neural network modeling of deflection basins.


• Sustainability of Transportation Infrstructure and Materials: I also have an avid interest in sustainability of asphalt materials and pavements. This is an emerging field, which has not been tied comprehensively to the pavement mechanics and materials research activities. I am particularly interested in the development of new asphalt materials, perperual pavements, and composite pavement systems within the framework of a life cycle performance model that integrates performance metrics throughout the materials and/or systems life cycle by reducing environmental impacts and energy use.


• Molecular Modeling and Nanoscale Testing:Molecular dynamics, neural networks, and Finite Element modleing, and nanoscale measurements (Nanoindentation and Mircoscopy - AFM, SEM, XRD) of properties of geo-pavement materials, additives, antistripping agents, and polymers