@article{zeng_underwood_clark_guddati_2024, title={Evaluation of Paris Law-Based approach on asphalt mixture reflective cracking performance modeling}, url={https://doi.org/10.1016/j.engfracmech.2024.110098}, DOI={10.1016/j.engfracmech.2024.110098}, journal={Engineering Fracture Mechanics}, author={Zeng, Zhe and Underwood, B. Shane and Clark, Jimmy D. and Guddati, Murthy}, year={2024}, month={Apr} }
 @article{zeng_kim_underwood_guddati_2024, title={Modeling damage caused by combined thermal and traffic loading using viscoelastic continuum damage theory}, volume={418}, ISSN={["1879-0526"]}, url={https://doi.org/10.1016/j.conbuildmat.2024.135425}, DOI={10.1016/j.conbuildmat.2024.135425}, abstractNote={Various engineering models have been proposed to mitigate fatigue cracking associated with thermal and traffic loadings, which are the two primary fatigue cracking mechanisms that negatively affect the service life of asphalt pavement. Thermal fatigue cracking is induced by cycles of temperature changes with relatively long time periods, which can be regarded as slow frequency sinusoidal loading. Traffic fatigue cracking is induced by numerous vehicle load repetitions and is often characterized using fast frequency sinusoidal loading. These two loading types occur simultaneously in the field. In order to investigate how to properly model the damage due to these two loading types, a set of tests that vary the load, frequency, and mode of testing was designed to mimic the scenarios that asphalt pavements experience under thermal loading and traffic loading separately and under the combined and simultaneous effects of both thermal and traffic loading. The viscoelastic continuum damage (VECD) model was applied to simulate the changes in material integrity under each condition. After determining the appropriate configuration for the proposed prediction model, the material integrity predictions were found to be accurate for the fast frequency tests but less accurate for the slow frequency tests. This difference is attributable to plasticity being a much more significant factor under slow frequency conditions than under fast frequency conditions. For the tests combining both fast and slow frequency conditions, the material integrity results oscillated continuously. It was postulated that these oscillations were due to the recovery mechanisms of asphalt concrete such as nonlinearity and healing. When the simplified viscoelastic continuum damage (S-VECD) model was applied, which does not consider the material’s recovery characteristics, the predicted material integrity was able to match the overall trend observed in the tests. Ultimately, a new way to model combined damage simultaneously under two cracking mechanisms (thermal fatigue cracking and traffic fatigue cracking) is introduced in this paper.}, journal={CONSTRUCTION AND BUILDING MATERIALS}, author={Zeng, Zhe and Kim, Y. Richard and Underwood, B. Shane and Guddati, Murthy}, year={2024}, month={Mar} }
 @article{chen_zeng_wang_zhang_2023, title={Asphalt Binder Fatigue Life Estimation Based on Energy Principles}, volume={35}, ISSN={["1943-5533"]}, DOI={10.1061/(ASCE)MT.1943-5533.0004740}, abstractNote={The linear amplitude sweep (LAS) test is considered a useful tool for evaluating the fatigue of asphalt binders. A challenge in the LAS test is that although the strain amplitude sweep test is set to load from 0% to 30%, some high cracking-resistant asphalt binders do not show significant damage level and instead exhibit behavior within the prefailure conditions. To solve this problem, experiments can be performed by increasing the strain to a higher level or change the control mode to stress control. In this study, a 60% strain level control mode is added in addition to the standard 30% strain level control mode. The stress-controlled mode amplitude sweep test was also carried out on nine different PG grade binders at three aging conditions and four temperatures. As the results showed, when using the maximum energy level to calculate fatigue life, Nf60@15% is about 99% of Nf30@15%. The fatigue life calculated based on the energy principle can well unify the results of the stress-controlled test and the strain-controlled test. The fatigue life obtained by the energy principle does not depend on the control mode of testing, which can also reflect the aging and temperature effect on the fatigue performance of asphalt binder. Comparing the fatigue parameter among the fatigue life using the energy criterion, GR-based criterion, and Glover-Rowe (G-R) parameter, the fatigue life calculation method using the energy fatigue criterion can best eliminate the influence of loading history.}, number={5}, journal={JOURNAL OF MATERIALS IN CIVIL ENGINEERING}, author={Chen, Hui and Zeng, Zhe and Wang, Rui and Zhang, Derun}, year={2023}, month={May} }
 @article{zeng_kim_underwood_guddati_2023, title={Asphalt mixture fatigue damage and failure predictions using the simplified viscoelastic continuum damage (S-VECD) model}, volume={174}, ISSN={["1879-3452"]}, url={https://doi.org/10.1016/j.ijfatigue.2023.107736}, DOI={10.1016/j.ijfatigue.2023.107736}, abstractNote={Fatigue cracking is a primary asphalt pavement distress and various models have been developed to predict the fatigue life of asphalt mixtures using laboratory tests. One such model is the simplified viscoelastic continuum damage (S-VECD) model, which has been implemented in the pavement performance prediction program, FlexPAVETM. The S-VECD model test protocols (AASHTO TP 133 and AASHTO T 400) and data processing tool (FlexMATTM) are widely used around the world. Over the past three decades, this model has been continuously improved and refined. However, questions remain on the model’s ability to predict the material response when stress or strain are used as the model input. Also, different fitting procedures for the model calibration were found to affect the model’s prediction accuracy. In this study, analysis was conducted using data for four typical North Carolina mixes based on single replicate tests and multiple replicate tests to compare the model’s prediction accuracy based on stress versus strain as the model input and by considering fitting errors in the different calculations. The results show that using strain as the model input, which automatically incorporates portions of permanent strain, yields more accurate predictions compared to using stress as the input, regardless of the fitting algorithm. Additionally, in the analysis of individual test data, which is not affected by replicate specimen variability, the model’s predictions match the measured data well, as long as the fitting errors of the damage characteristic curve are controlled. When the data from replicate tests are analyzed together, although specimen variability compromises the S-VECD model’s prediction accuracy, failure can still be reasonably determined when strain is used as the model input.}, journal={INTERNATIONAL JOURNAL OF FATIGUE}, author={Zeng, Zhe and Kim, Y. Richard and Underwood, B. Shane and Guddati, Murthy}, year={2023}, month={Sep} }
 @article{zeng_liu_zhang_2023, title={Critical evaluation of unit response function interconversions for asphalt concrete linear viscoelastic modeling using discrete spectrum}, volume={382}, ISSN={["1879-0526"]}, DOI={10.1016/j.conbuildmat.2023.131301}, abstractNote={It is well-known that asphalt concrete has three unit response functions (URFs): complex modulus, relaxation modulus, and creep compliance. The interconversions among these three URFs are generally done through discrete relaxation/retardation spectrum. Since different methods of determining discrete spectrum have been developed in the past, this study focused on systematically comparing and evaluating three classical methods: collocation, multidata, and windowing methods, with four relaxation/retardation time selections. Additionally, considering theoretical requirement and practical preference, both wide and narrow relaxation/retardation time ranges are evaluated to quantify their influences on the result qualities. After multiple sets of result comparisons, it has been found that all three methods can lead to reasonable results as long as wide and appropriate relaxation/retardation time range is given. However, since in practice shorter time range may be used more often, in this scenario attention needs to be paid to the solution quality including the spectrum values and shape, and the characterized function accuracy. Overall, the windowing method causes fewer solving issues than the other two methods due to its optimization nature, which prohibits the negative relaxation/retardation strength values. Despite that, the collocation and multidata methods occasionally lead to more reasonable results when narrower relaxation/retardation time range is used. From these observations, a hybrid procedure, which takes advantage of each interconversion method, is proposed in this study to optimize the discrete spectrum determination for asphalt concrete.}, journal={CONSTRUCTION AND BUILDING MATERIALS}, author={Zeng, Zhe and Liu, Bin and Zhang, Derun}, year={2023}, month={Jun} }
 @article{xu_zeng_miao_zhang_fu_2023, title={Field Aging Characterization of Asphalt Pavement Based on the Artificial Neural Networks and Gray Relational Analysis}, volume={35}, ISSN={["1943-5533"]}, url={https://doi.org/10.1061/JMCEE7.MTENG-15004}, DOI={10.1061/JMCEE7.MTENG-15004}, abstractNote={Accurate characterization of field aging of asphalt pavement is critical to precisely assessing its in-service performance. However, most of the traditional test/predictive methods either cannot fully capture the field aging characteristics or involve costly testing/computational efforts to ensure satisfactory prediction accuracy. To alleviate these problems, this study developed a new field aging predictive model based on artificial neural networks (ANNs) and gray relational analysis (GRA), which takes the field-aged viscosity of asphalt binder as the target predictive property. A series of influencing factors that may affect the field-aged viscosity were systematically investigated, among which the eight most significant ones were screened out for the ANN modeling through the GRA. A total of 479 data extracted from long-term pavement performance (LTPP) database were used for the training, validation, and testing of the ANN model. The calculation results showed that the predictive model developed using the ANN approach provided a high prediction accuracy with R2 value greater than 0.90. Furthermore, the falling-weight deflectometer (FWD) data collected from the database were utilized to evaluate the predictive performance of the well-trained ANN model. Consistent results were obtained between the viscosity values predicted from the ANN model and those back-calculated from the FWD data, indicating that the newly developed field aging model has the capability to accurately characterize the field aging evolution of asphalt pavement.}, number={7}, journal={JOURNAL OF MATERIALS IN CIVIL ENGINEERING}, author={Xu, Peixin and Zeng, Zhe Alan and Miao, Yu and Zhang, Derun and Fu, Chaoliang}, year={2023}, month={Jul} }
 @article{sudarsanan_zeng_kim_2023, title={Laboratory investigation into the crack propagation mechanism of geosynthetic reinforced asphalt concrete using digital image correlation technique}, volume={24}, ISSN={["1477-268X"]}, url={https://doi.org/10.1080/10298436.2023.2251079}, DOI={10.1080/10298436.2023.2251079}, abstractNote={ABSTRACT Geosynthetic reinforcement has proven effective in mitigating reflective cracking in new pavement overlays. This study aimed to compare the ability of five different geosynthetic reinforcement products to alleviate cracking in overlays. Each product was sandwiched within a two-layered asphalt concrete (AC) beam specimen and subjected to a four-point notched beam fatigue test. The study monitored crack propagation, understood crack propagation mechanisms, and quantified crack lengths in different geosynthetic-reinforced AC beam specimens during a notched beam fatigue test using the digital image correlation (DIC) technique. The DIC analysis generated full-field displacement and strain contours, depicting the damage mechanisms of geosynthetic reinforcement products in AC overlays under fatigue loading. The quantitative analysis measured the cracked areas caused by each product. The interfacial damage observed in various geosynthetic-reinforced beam specimens under different test conditions suggested that the failure modes of AC beam specimens reinforced with different products varied, and choosing the right product for a project depended on the pavement conditions, geosynthetic product properties, and tack coat properties. Finally, the predictive algorithms presented in this paper allow for predicting the failure mode generated by different geosynthetic products for different overlay conditions in the field, providing valuable insight for pavement engineers.}, number={1}, journal={INTERNATIONAL JOURNAL OF PAVEMENT ENGINEERING}, author={Sudarsanan, Nithin and Zeng, Zhe Alan and Kim, Youngsoo Richard}, year={2023}, month={Dec} }
 @article{zeng_underwood_castorena_2022, title={Low-temperature performance grade characterisation of asphalt binder using the dynamic shear rheometer}, volume={23}, ISSN={["1477-268X"]}, url={https://doi.org/10.1080/10298436.2020.1774766}, DOI={10.1080/10298436.2020.1774766}, abstractNote={ABSTRACT Currently, the bending beam rheometer (BBR) test is the standard method for evaluating the low-temperature performance grade (PG) of asphalt binders. Despite its use, there are limitations with the BBR test with respect to the amount of asphalt binder needed for test specimens, the relative difficulty in preparing specimens, and the overall testing efficiency. On the contrary, the dynamic shear rheometer (DSR) is an efficient test method that is widely used to determine the PG at intermediate and high temperatures. In this study, DSR temperature-frequency sweep tests using the 8-mm parallel plate is proposed as an alternative to the BBR. The method takes advantage of the time-temperature superposition principle and linear viscoelastic interconversion to predict the BBR creep stiffness and m-values at 60 s from the modulus and phase angle measured by the DSR at intermediate temperatures. Two conversion methods were used to verify the ability to predict BBR properties using DSR testing based on 45 binders of diverse PG. The DSR-based method yields good agreement with measured BBR data. On average, the continuous low-temperature PG predicted using the DSR method is within 2.7°C of that measured using the BBR.}, number={3}, journal={INTERNATIONAL JOURNAL OF PAVEMENT ENGINEERING}, author={Zeng, Zhe 'Alan' and Underwood, B. Shane and Castorena, Cassie}, year={2022}, month={Feb}, pages={811–823} }
 @article{zeng_zhang_liu_2021, title={Development of an energy-based framework to determine the surface free energy of asphalt binder: theoretical models}, volume={54}, ISSN={["1871-6873"]}, DOI={10.1617/s11527-021-01834-3}, number={6}, journal={MATERIALS AND STRUCTURES}, author={Zeng, Zhe and Zhang, Derun and Liu, Hanqi}, year={2021}, month={Dec} }
 @article{zhang_luo_zeng_2019, title={Characterization of surface free energy of mineral filler by spreading pressure approach}, volume={218}, ISSN={["1879-0526"]}, DOI={10.1016/j.conbuildmat.2019.05.128}, abstractNote={Surface free energy of mineral filler plays an important role in evaluating the adhesion of asphalt mastic (mineral filler plus asphalt binder), which is usually measured through the capillary rise approach. However, this approach has been verified to hold only for the low energy materials, which does not apply to the high energy mineral filler. To overcome this limitation, the paper devises a new approach for measuring the surface free energy of the mineral filler based on a generalized Washburn equation. First, a reference liquid is selected to conduct the vapor adsorption test on the mineral filler to measuring its spreading pressure, in which a modified Brunauer-Emmett-Teller (BET) model is employed to determine the filler specific surface area. This reference liquid is again used to perform the capillary rise measurement to calculate the resultant effective capillary radius of the filler bed. Three independent liquids are subsequently selected to conduct the capillary rise test to measure their spreading pressure values with respect to the same mineral filler. By substituting the measured spreading pressure values of the three liquids into the Good-van Oss-Chaudhury (GvOC) equation, the surface free energy components of the mineral filler are finally determined. This newly developed approach is then successfully applied to measure the surface free energy for four typical types of the mineral filler. The moisture susceptibility rankings obtained from the energy ratios of the proposed approach are experimentally found to be consistence with those measured from a standard moisture susceptibility test for the corresponding asphalt mastics. In this regard, the proposed approach is believed to be capable of accurately characterizing the surface free energy of the mineral filler.}, journal={CONSTRUCTION AND BUILDING MATERIALS}, author={Zhang, Derun and Luo, Rong and Zeng, Zhe}, year={2019}, month={Sep}, pages={126–134} }