@article{cho_karshenas_tayebali_guddati_kim_2017, title={A mechanistic approach to evaluate the potential of the debonding distress in asphalt pavements}, volume={18}, ISSN={["1477-268X"]}, DOI={10.1080/10298436.2016.1149837}, abstractNote={Abstract The debonding distress in asphalt pavement structures is a critical problem that affects the performance of asphalt concrete pavements. It occurs at the layer interface due to the poor bond quality between adjacent asphalt concrete layers and/or when stresses at the layer interface exceed the strengths of the material at the interface. The debonding of the adjacent layers, especially the top surface layer of an asphalt pavement, is a contributing factor to the premature cracking of pavements. Hence, the debonding distress can lead to a reduction in the life of the pavement. This paper presents an analytical and experimental framework to evaluate the potential for debonding at the layer interface of asphalt concrete pavements. Computational analysis was performed to determine the critical stress and strain states in layered asphalt pavements under moving vehicle loads using the Layered ViscoElastic pavement analysis for Critical Distresses (LVECD) computer program developed at North Carolina State University. This computational analysis enables a greater understanding of the critical stress that is involved in debonding and the ways that such stress is affected by pavement design parameters and environmental conditions. In addition, a prediction model was developed that can determine the shear bond strength at the interface of asphalt concrete layers with different tack coat materials at various temperatures, loading rates and normal confining stresses. The systematic and mechanistic framework developed in this study employs the maximum shear ratio concept as a shear failure criterion and provides a tool to evaluate the effects of various loading, environmental and pavement factors on the debonding potential of asphalt pavements. The overall advantages of the mechanistic framework and approach using the LVECD analysis tool will help lead to better understanding of the debonding mechanism, proper selection of the tack coats, and economic benefit in highway pavement maintenance and rehabilitation costs.}, number={12}, journal={INTERNATIONAL JOURNAL OF PAVEMENT ENGINEERING}, author={Cho, Seong-Hwan and Karshenas, Afshin and Tayebali, Akhtarhusein A. and Guddati, Murthy N. and Kim, Y. Richard}, year={2017}, pages={1098–1110} }
 @article{cho_safavizadeh_kim_2017, title={Verification of the applicability of the time-temperature superposition principle to interface shear stiffness and strength of GlasGrid-reinforced asphalt mixtures}, volume={18}, ISSN={["2164-7402"]}, DOI={10.1080/14680629.2016.1189350}, abstractNote={This paper aims to verify the applicability of the time–temperature superposition (t–TS) principle to the interface shear performance of GlasGrid-reinforced asphalt specimens under monotonic and random cyclic shear loading. A double shear tester and a direct shear device, the Modified Advance Shear Tester that has the capability to apply confining loads, were used to fulfil this objective. Double-layered asphalt specimens were fabricated and reinforced using two types of fibreglass grids with 12.5-mm and 25-mm grid openings, respectively. PG 64-22 asphalt binder was used as the tack coat when the smaller opening grid was used, and SS-1 emulsion was applied as the tack coat when the larger opening grid was used. Approaches that employ the mixture dynamic modulus, tack coat residue complex modulus, and interface shear modulus shift factors for shifting the shear test results and constructing shear master curves were evaluated. The results show that the t–TS principle is applicable to the shear strength and shear stiffness of GlasGrid-reinforced asphalt concrete specimens if the right shift factor function is used.}, number={4}, journal={ROAD MATERIALS AND PAVEMENT DESIGN}, author={Cho, Seong Hwan and Safavizadeh, Seyed Amirshayan and Kim, Y. Richard}, year={2017}, month={Jul}, pages={766–784} }
 @article{cho_kim_2016, title={Verification of Time-Temperature Superposition Principle for Shear Bond Failure of Interlayers in Asphalt Pavements}, ISSN={["2169-4052"]}, DOI={10.3141/2590-03}, abstractNote={ Asphalt pavement structures are composed of different asphalt concrete layers with surface layers that are bonded together with a tack coat. Thus, interlayer bonding between pavement layers is a key factor that affects the performance of any pavement structure. However, relatively little attention has been given to the characterization and modeling of interlayer bonding or to associated test methods that can be used in the laboratory to evaluate the bond strength between asphalt concrete layers. This paper presents a test method for evaluating interface bonding between asphalt concrete layers in shear mode. Moreover, the time–temperature superposition (t-TS) principle with growing damage in shear failure mode is examined to characterize the shear bond strength of asphalt concrete pavements for a wide range of temperatures. The subsequent validation of the t-TS principle allows the shear bond strength between asphalt layers at various temperatures and loading rates to be determined with only three or four shear tests. Comparison of the shear stress values calculated from a mechanistic pavement analysis program for a critical condition with the shear strength values at the condition determined from the prediction model developed in this study can provide the foundation for a mechanistic design to prevent shear bond failure between asphalt layers. }, number={2590}, journal={TRANSPORTATION RESEARCH RECORD}, author={Cho, Seong-Hwan and Kim, Y. Richard}, year={2016}, pages={18–27} }
 @article{cho_im_2015, title={Mathematical Approach in Rheological Characterizing of Asphalt Emulsion Residues}, volume={2015}, ISSN={["1563-5147"]}, DOI={10.1155/2015/797808}, abstractNote={Three different emulsion residues, such as SS1HP, HFE90, and SS-1VH (trackless), and a base asphalt binder (PG 64-22) are compared to characterize rheological properties by using DSR test. In order to capture the emulsion properties, different frequencies (from 1 to 100 rad/sec at a 10% constant shear rate) and temperatures (from −45°C to 75°C with 15°C increments) were applied. Then, a master curve for shear modulus was plotted for each emulsion. The transition of the HFE90 emulsion from viscous to elastic behavior occurs at lower temperatures, compared to the other materials. This emulsion is known for performing in a wider temperature range as shown in the results. The trackless emulsion presents an elastic behavior at intermediate temperatures. This product is known as having very fast setting and high resistance to shear stresses. The trackless emulsion presents the highest viscous and elastic modulus, followed by the PG 64-22 binder, SS1HP, and HFE90 emulsion. Shear strength test results show a behavior between trackless emulsion and SS1HP similar to the frequency sweep test results performed by DSR.}, journal={MATHEMATICAL PROBLEMS IN ENGINEERING}, author={Cho, Seong Hwan and Im, Jeong Hyuk}, year={2015} }
 @article{karshenas_cho_tayebali_guddati_kim_2014, title={Importance of Normal Confinement to Shear Bond Failure of Interface in Multi layer Asphalt Pavements}, ISSN={["2169-4052"]}, DOI={10.3141/2456-17}, abstractNote={Several direct shear test devices are used to evaluate the shear bond strength of tack coat materials in interlayer bonding in asphalt pavements. Some devices have the capability of evaluating strength in direct shear with normal confinement, whereas other devices do not have that capability or use passive confinement to evaluate the interlayer bond strength. The literature indicates that interlayer bond strength increases with the application of normal confinement. However, the question remains as to the level of normal confinement, if any, that should be used in direct shear testing to evaluate the interlayer bond strength for specification acceptance or design. This study presents a methodology to interpret laboratory bond strength test results in relation to the state of stress at the layer interface in a representative pavement section. The results confirm the importance of normal confinement for shear bond strength evaluation and provide guidance for the selection of the appropriate level of normal confinement.}, number={2456}, journal={TRANSPORTATION RESEARCH RECORD}, author={Karshenas, Afshin and Cho, Seong-Hwan and Tayebali, Akhtarhusein A. and Guddati, Murthy N. and Kim, Y. Richard}, year={2014}, pages={170–177} }