Aging has a significant effect on the performance of asphalt material. Reliable modelling of the change of asphalt mixture properties over time is crucial to evaluating and predicting the performance ...of the designed pavement. The objective of this study is to develop an aging model to accurately predict the cracking performance of asphalt mixtures over the pavement service life, as well as evaluate the aging susceptibility of mixtures over time. In this study, nine loose mixtures were conditioned in an oven at 95 °C for multiple durations to simulate different field aging times. The climatic aging index (CAI) developed by the National Cooperative Highway Research Program (NCHRP) 09-54 project was utilized to calculate the appropriate field aging durations corresponding to the different laboratory aging conditions. Complex modulus tests (
E
*) were conducted to measure the rheological properties of the conditioned mixtures and further construct the dynamic modulus and phase angle mastercurves. The mixture Glover–Rowe (
G
–
R
m
) parameter, incorporating both stiffness and relaxation capacity, was selected and used as the Aging Index Property to model the changes in mixture cracking properties with aging. The results of this study indicate that the developed mixture aging model can effectively capture the two aging reaction periods (fast and constant) of asphalt materials. The developed model can not only be used to evaluate the change of cracking properties over pavement service life, but also detect the aging susceptibility of asphalt mixtures.
LiDAR technology, increasingly prevalent in various applications, has not been significantly used for assessing pavement elevation changes due to frost-induced heaves. This research examines the ...efficiency and accuracy of LiDAR sensors mounted on an Unpiloted Aerial System (UAS) to measure pavement frost heaves in remote cold climate regions. Experiments on simulated heaves and actual pavement sections assessed flight pattern data gathering protocols and data processing methods. Optimal measurements of simulated frost heave were achieved with a 45m altitude, 2m/s ground speed, and 10cm x 10cm spatial resolution. The finalized protocol was applied to in-service pavement sites in a cold climate region, comparing seasonal results to demonstrate the ability of LiDAR sensors to capture frost-induced heaving on road surfaces. The study shows that UAS-LiDAR can reliably capture vertical deviations due to surface roughness, supporting the development of an automated system to measure pavement roughness caused by frost heave distresses.
This work presents the development of new fatigue performance indices for asphalt binders based on viscoelastic continuum damage (VECD) theory and failure energy. Five plant-produced asphalt mixtures ...were subjected to three different conditioning levels (short-term ageing during production and loose mix ageing for 5 and 12 days at 95°C in the laboratory) and the corresponding binders were extracted and recovered. Direct Tension Cyclic Fatigue (DTCF) tests were performed on the mixtures to characterise the mixture fatigue properties using the simplified viscoelastic continuum damage (S-VECD) analysis approach. Frequency and temperature sweep tests and the Linear Amplitude Sweep (LAS) test using a Dynamic Shear Rheometer (DSR) were conducted on the recovered binders to evaluate the binder rheological and fatigue properties. Three new performance indices are explored from the LAS test: Strain Tolerance (ε
T
), Strain Energy Tolerance (Ε
f
), and Average Reduction in Integrity to Failure (I
R
). These indices were used to track the evolution of binder fatigue properties with ageing. A unique aspect of these indices is that they capture the failure point of the binder during the LAS test and combine the stress and strain histories of the material. Compared with the traditional A and B parameters from the LAS test, the new indices show a consistent decrease in the fatigue properties of the binders with ageing. The newly proposed parameters show improved correlations with mixture fatigue performance index (D
R
) from the DTCF test, indicating their potential for evaluation of asphalt mixture fatigue properties. In addition, the new indices developed from this study have been shown to effectively capture the ageing gradient within the pavement structure and can also be used together with the binder rheological indices (e.g. G-R parameter and ΔTc) to evaluate both environmental and fatigue cracking of asphalt pavements at the same time.
AbstractThe first step toward building pavement structures that are resilient to flooding is to have a proper understanding of the impact of inundation on the pavement. Depth-damage functions have ...been developed and are widely used to quantify flood-induced damage to buildings. However, such damage functions do not exist for roadway pavements. The objective of this study is to develop a methodological framework to model postflooding road damage by identifying the importance of several parameters including flood duration, flood depth, flood pattern (including real flood data), transfer functions, pavement materials, and analysis location. Pavement serviceability and costs are introduced into the evaluation as well. The long-term goal is a tool for decision makers to use in planning and management of flooding events for more resilient pavements and allocation of budgets. It is established that the most important parameters that should be accounted for by decision makers are the flood duration, combination of the materials, critical location on the roadway (both vertical and lateral), and use of appropriate transfer functions. Opening the roadway to traffic immediately after the floodwater recedes will lead to earlier and more significant deterioration of the pavement and more costly maintenance and reconstruction.
The present study aims to evaluate binder and mixture testing methods for capturing the compatibility of complex asphalt materials consisting of different virgin binder sources, reclaimed asphalt ...pavement (RAP) materials and recycling agents (RA). Binder evaluation methods include the saturate, aromatic, resin and asphaltene (SARA) fractionation, advanced polymer chromatography (APC) analysis, differential scanning calorimeter (DSC) and rheological measurements. Mixture performance tests include the complex modulus (E*), direct tension cyclic fatigue (DTCF), disk-shaped compact tension (DCT) and semi-circular bending (SCB) fracture tests. The results from the testing and analysis indicate that the rheological characterisation of asphalt binder or mixture may not capture the incompatibility between virgin binder, RAP and RA. Binder DSC analysis as well as mixture fracture tests have shown promise to evaluate the compatibility of complex asphalt materials with different virgin binders, RAP and RA, as well as the effect of incompatibility on mixture performance.
Aging can significantly affect the performance of asphalt mixtures, causing increase in stiffness, reduction in relaxation capability and increase in cracking susceptibility. It is also well known ...that fundamental viscoelastic properties are used for design and modelling of asphalt mixtures and pavement structures to addressing rutting, fatigue and thermal cracking concerns. The objective of this paper is to study how the viscoelastic properties of asphalt mixture change over time, and evaluate and identify the cracking and aging susceptibility of asphalt mixtures with different mix variables during material selection and mixture design. Ten mixtures are evaluated using different laboratory conditioning protocols to simulate a range of aging levels in the field. The complex modulus test is then conducted on the lab aged mixtures to measure the viscoelastic properties in order to construct the dynamic modulus and phase angle master curves. The mixture Glover-Rowe (G-Rm) parameter and the shape parameters of the dynamic modulus and phase angle master curves, including inflection point frequency (−β/γ), difference between the glassy modulus and the inflection point modulus (γ), peak value of phase angle (a) and the horizontal position (frequency) of the peak phase angle value (c), are determined and evaluated for the mixtures with different aging conditions and mix variables. The study indicates the ability of the G-Rm parameter and all the master curve shape parameters to capture the effect of different aging conditions on linear viscoelastic mixture properties, as well as the cracking and aging susceptibility of asphalt mixtures.
•Rheological parameters can capture the cracking and aging susceptibility of asphalt mixtures.•Mixtures with higher initial relaxation capability and better cracking performance have the tendency to age more severely.•The G-Rm parameter can be used as a performance index to indicate the propensity for crack initiation of asphalt mixtures.
The mechanical properties of Bituminous Stabilized Materials (BSMs) have been widely studied in the past, however the influence of temperature on their non-linear constitutive properties has never ...been addressed. In this research, the role of temperature on the mechanical properties of a BSM prepared with asphalt emulsion and hydrated lime was investigated. Triaxial shear strength tests were performed at different temperatures and confining pressures. The experimental results allowed the development of finite element models defining the local stress and temperature-dependent mechanical properties. An approach for incorporating plasticity and temperature effects through a 2D axisymmetric finite element model of multilayer pavement was developed. Three pavement structures were subjected to the same load applications at different temperatures. Their responses were compared to determine the most critical scenario. In conclusion, plasticity and temperature are key factors for BSMs analysis and design while linear-elastic assumptions lead to overestimating the service life of rehabilitated pavements.
This paper presents an augmented full quadratic model (AFQM), artificial neural network (ANN) and an innovative machine learning technique called self-validated ensemble modelling (SVEM) approaches ...to predict low-temperature fracture energy of asphalt mixtures. An experimental database including 852 fracture energy values obtained from low temperature disk-shaped compact tension (DCT) testing was utilised to develop the prediction models. The fracture energy was predicted in terms of several variables that are available during the mix design process. The collected data were categorised into three groups based on the availability of the data at different points during the mix design process. A sensitivity analysis was conducted to assess the impact of the design variables on fracture energy. Based on the model development results, both ANN and SVEM methods showed higher prediction accuracy than AFQM. Prediction models based on the ANN were time-consuming and computationally expensive due to the optimum model architecture. The SVEM technique was found to be a reliable prediction method with high prediction reliability even with a limited amount of data. Based on the sensitivity analysis, design traffic level, PG low temperature (PGLT) binder grade, amount of aggregate passing 9.5 mm sieve, and the voids in mineral aggregate (VMA) are the most effective factors impacting low-temperature asphalt mixture fracture energy. A web-based prediction model platform was developed using prediction models based on the SVEM technique which can be utilised as a predesign tool to evaluate low-temperature fracture energy of asphalt mixtures when laboratory testing is not feasible.
Use of the semi-circular bending (SCB) test has gained popularity for evaluating cracking performance of asphalt mixtures. An Illinois Flexibility Index Test (I-FIT) variant of SCB has shown the ...ability to distinguish mixtures through use of the flexibility index (FI) parameter. While this index has been able to rank the mixtures with respect to performance, a high coefficient of variation (COV) among the replicates has often been observed. Furthermore, parameters such as total fracture energy and FI do not incorporate rate dependency of fracture processes which are very important for viscoelastic materials such as asphalt mixtures at low and intermediate temperatures. In light of these observations, a rate-dependent cracking index (RDCI) is proposed that utilises cumulative fracture work potential and instantaneous power calculated from the I-FIT test to assess impulse of the mixture. Thus, in spirit, this parameter captures the fracture energy and crack velocity of the material; however, these are calculated in a rate-dependent manner. A total of 18 surface course mixtures were analysed using the RDCI and resulted in an average overall reduction of 10.6% in COV as compared to FI while maintaining similar ranking of mixtures. In general, RDCI was able to better discriminate the 18 mixtures as compared to FI. The evaluation of five mixtures at three aging levels showed the robustness of RDCI in capturing effects of aging on fracture behaviour of asphalt mixtures.
AbstractThe purpose of this study was to conduct a performance evaluation to investigate the effect of a newer type of asphalt binder modification system and to demonstrate the importance of ...performance prediction modeling over use of only mix stiffness or a single performance index property to compare asphalt binder modification systems. Four asphalt mixtures with different amount of modifiers were evaluated in this study. Laboratory characterization included complex modulus, direct tension cyclic fatigue, cracking tolerance index, disk-shaped compact tension, indirect tensile creep and strength, and Hamburg wheel tracking tests. In addition, advanced performance prediction programs including AASHTOWare Pavement ME, FlexPAVE, and IlliTC were utilized to predict mixture performance. Based on the results of laboratory testing and performance simulations, the reactive isocyanate-based modifier (RIB) and styrene-butadiene-styrene (SBS) modifiers improved the properties and performance of the control mixture with respect to rutting and fatigue cracking but may have a negative effect with respect to thermal cracking. Modification of the control mixture with the combination of RIB and SBS balanced good rutting and fatigue cracking performance while maintaining thermal cracking resistance, indicating that the RIB + SBS modification may be a good candidate for further evaluation and field trial consideration.
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