Performance Of Asphalt Concrete Pavements Research Articles

Effect of air voids and asphalt content changes on laboratory and simulated long-term fatigue performance of asphalt concrete pavements

Effect of air voids and asphalt content changes on laboratory and simulated long-term fatigue performance of asphalt concrete pavements

Prediction of stiffness modulus of bituminous mixtures using the applications of multi-expression programming and gene expression programming

An essential factor in the design and in situ performance of asphalt concrete pavements is its elastic-stiffness properties. The objective of the present study, is to develop empirical equations to estimate indirect tensile stiffness modulus (ITSM) of bituminous mixture using the soft computing techniques of multi expression programming (MEP) and gene expression programming (GEP). The soft computing models were developed using experimental data points containing laboratory and field blended dense-graded hot mix asphalt (HMA) and gap-graded stone matrix asphalt (SMA) mixtures including three asphalt binders. The dominant parameters covered mix physical and volumetric properties, test temperatures, and the mix variables needed during quality control and assurance assessments. The soft computing models could successfully estimate the stiffness modulus with notable values of R values between 0.835 and 0.944. The GEP equations estimated the elastic stiffness modulus with a higher rate of accuracy when compared to the MEP, non-linear and linear regression estimates.

EVALUATION OF MARSHAL STABILITY AND FLOW OF HYBRID MODIFIED ASPHALT CONCRETE

Highway engineers and researchers are constantly trying to enhance the performance of asphalt concrete pavement, in order to keep up with the global adequate and sustainable highway infrastructure drive. Modification of asphalt concrete could improve certain properties of the mixture and reduce cost of road construction materials. In this research, evaluation of Marshal Stability and flow of hybrid asphalt modified concrete was studied, the wastes from various industries such steel industry, plastic industry and coal-fired power plant industries were combined together to form hybrid composite. Steel slag, fly ash, waste plastic, aggregate and bitumen were used to produce the asphalt concrete in a hybrid manner to evaluate effect of stability and flow properties of asphalt concrete mixture. The physical properties of steel slag, fly ash aggregate, bitumen and waste plastic based polypropylene were determined by carrying out tests such as sieve analysis, moisture content, flakiness and elongation, aggregate impact, aggregate crushing, specific gravity, hygrometer, penetration, softening point, flash and fire point, viscosity, ductility and water-in-bitumen test. Bitumen with penetration grade 60/70 was used and the content varied from 5.0 to 7.0 % at 0.5% interval. A cylindrical sample with the composite mixture of asphalt concrete was produced using varying proportions of hybrid composite which comprises of steel slag (SS) and fly ash (FA) at 2%, 4%, 6% and 8% by weight of the asphalt concrete to partially replace the conventional materials (aggregate and filler) and bitumen which was partially replaced with polypropylene (PP) at 5%, 10%, 15% and 20% respectively. The Marshal Stability test conducted on the hybrid composite asphaltic concrete gives optimum stability values of 10.50 kN, 12.50 kN, 12.30 kN and 13.50 kN and optimum flow values of 3.30 mm, 2.80 mm, 2.80 mm, and 2.70 mm at 2%, 4%, 6% and 8% respectively. Comparing with Asphalt Institute specification, the non-conventional material used as fillers, coarse and fine aggregate can be conveniently used in light, medium and heavy traffic. Based on the findings, the application of these wastes material which constitute higher stability and flow will improve the properties of asphalt concrete, reduce the cost of constituent material and decrease environmental problem that arise from various industries.

Performance of Asphalt Concrete Pavement Reinforced with High-Density Polyethylene Plastic Waste

This research investigates the possibility of using high-density polyethylene (HDPE) plastic waste to improve the properties of asphalt concrete pavement. HDPE plastic waste contents of 1, 3, 5, and 7% by aggregate weight were used. HDPE plastic waste=stabilized asphalt concrete pavement (HDPE-ACP) was evaluated by performance testing for stability, indirect tensile strength, resilient modulus (MR), and indirect tensile fatigue (ITF). In addition, microstructure, pavement age, and CO2 emissions savings analyses were conducted. The performance test results of the HDPE-ACP were better than those without HDPE plastic waste. The optimum HDPE plastic waste content was 5%, offering the maximum MR, ITF, and pavement age. Scanning electron microscope images showed that the excessive HDPE plastic waste content of 7% caused a surface rupture of the sample. Improvements in the pavement age of the HDPE-ACP samples were observed compared with the samples with no HDPE plastic waste. The highest pavement age of the HDPE-ACP sample was found at an HDPE plastic waste content of 5% by aggregate weight. The CO2 emissions savings of the sample was 67.85 kg CO2-e/m3 at the optimum HDPE plastic waste content.

Mechanical properties of asphalt concrete modified with carbon nanotubes (CNTs)

Three different percentages of carbon nanotubes (CNTs) (0.1%, 0.5%, and 1% by mass of asphalt cement) were used to modify conventional asphalt cement (60/70) in this study. Mechanical properties of modified asphalt cement and mixture were evaluated. Penetration grade, kinematic viscosity, softening point and dynamic shear rheometer test were measured to evaluate physical properties of modified asphalt cement. The results exhibited that modifying asphalt cement with CNTs decreased its penetration and increased its kinematic viscosity and softening point. Rutting parameter increased with CNTs at the given temperature for both unaged and RTFOT-aged samples. Marshall stability tests, low temperature cracking tests, indirect tensile tests and wheel tracking tests were conducted to assess the mechanical performance of modified hot asphalt mixture. The Marshall stability increased with CNTs but no significant difference at 0.5 and 1.0 wt%, while Marshall flow decreased with CNTs. The results of wheel tracking test showed that rut depth decreased by 45% upon adding 0.5% CNTs by weight of asphalt cement; also, this percentage of CNTs endowed improvement in low temperature cracking and indirect tensile strength of the asphalt concrete. This study underlines that adding CNTs into asphalt cement enhances the performance of asphalt concrete pavement in both hot and cold weather, which in turn prolongs the pavement’s service life and saves maintenance expenses.

Numerical modelling of rutting performance of asphalt concrete pavement containing phase change material

Numerical modelling of rutting performance of asphalt concrete pavement containing phase change material

Effectiveness of bagasse ash for performance improvement of asphalt concrete pavements

The performance of asphalt concrete pavements (ACP) is greatly related to the rate of rutting. Stone dust is mostly used as a filler in ACP. Bagasse ash being cementitious in nature, and costless waste can also be used as a filler. The overall aim is to select a suitable filler for better performance of asphalt concrete pavements. The effectiveness of locally available bagasse ash is examined as a filler for asphalt concrete in terms of its effect on job mix formula, stability, rutting depth, the rise in temperature, and cost of asphalt concrete. All tests are performed as per AASHTO standards. The bagasse ash asphalt concrete showed a reduction in rutting depth, temperature rise, and cost as compared to that of the stone dust asphalt concrete without disturbing the job mix formula. Hence, bagasse ash can be helpful for the performance enhancement of asphalt concrete pavements.

Investigation on the Temperature Distribution of Asphalt Overlay on the Existing Cement Concrete Pavement in Hot-Humid Climate in Southern China

Temperature is known to be one of the most important factors affecting the design and performance of asphalt concrete pavement. The distresses of asphalt overlay are closely related to its temperature, particularly in Guangxi, a hot-humid-climate region in China. This research is to analyze the impact of meteorological factors on temperature at 2 cm depth in asphalt overlay by ReliefF algorithm and also obtain the temperature prediction model using MATLAB. Two test sites were installed to monitor the temperatures at different pavement depths from 2014 to 2016; meanwhile, the meteorological data (including air temperature, solar radiation, wind speed, and relative humidity) were collected from the two meteorological stations. It has been found that the temperature at 2 cm depth experiences greater temperature variation, and the maximum and minimum temperatures of asphalt overlay, respectively, occur at 2 cm depth and on the surface. Besides, the results of ReliefF algorithm have also shown that the temperature at 2 cm depth is affected significantly by solar radiation, air temperature, wind speed, and the relative humidity. Based on these analyses, the prediction model of maximum temperature at 2 cm depth is developed using statistical regression. Moreover, the data collected in 2017 are used to validate the accuracy of the model. Compared with the existing models, the developed model was confirmed to be more effective for temperature prediction in hot-humid region. In addition, the analysis of rutting depth and overlay deformation for the two test sections with different materials is done, and the results have shown that reasonable structure and materials of asphalt overlay are vital to promote the high-temperature antideforming capability of pavement.

Using Phase Change Material to Improve Asphalt Pavement Behavior

This research is an attempt to use PCM technology in order to protect and treat the asphalt pavement from the influence of temperatures and thus not to crack the road pavements. Applying the phase change materials in roadway traffic domain is becoming an exploration research, although the PCM have been used in many fields. Depending on the properties of latent heat, we can apply the phase change materials to control and regulate temperature of asphalt pavement and keeping mix feasibility. Asphalt pavement is a material that can heat up to 60°C due to solar irradiation in summertime because of their excellent heat-absorbing properties. Using the PCM can treat the asphalt mixture pavement cracks related to temperature, enhance the performance of asphalt concrete pavement, and prolong the service life of asphalt concrete pavement. We address the procedure bitumen penetration grade 50/60 was used in this test. In this study, gravel and sand are used as coarse and fine aggregate respectively in hot mixture asphalt. In order to apply PCM in asphalt concrete pavement, mechanism of controlling temperature, road performance and mixture design method of asphalt mixture have been considered. Results show that maximum temperature of surface and bottom respectively is (43.41°C, 46.47°C), and the maximum absolute Delta (difference between surface and bottom) reached to 4.72°C.

Construction of complex shear modulus and phase angle master curves for aging asphalt binders

ABSTRACT Performance of asphalt concrete pavement significantly degrades during the aging of asphalt binders. The master curves of complex shear modulus and phase angle are recognised as useful tools to characterise the rheological properties of aging asphalt binders. The main shortcoming of existing master curves is that the effects of aging cannot be captured and predicted effectively. This study developed a new method to construct such aging master curves that can be extended to predict the complex shear modulus and phase angle at a wide range of aging time and temperature. The DSR tests were conducted on three different types of asphalt binders with three aging temperatures and four aging durations. The master curves of complex shear modulus and phase angle were constructed for aging asphalt binders through time-temperature-aging shift by performing both rotation and horizontal aging shift. Rotation and horizontal aging shift were determined as the function of aging time and aging temperature. Therefore, it becomes possible and convenient to construct single aging master curves at a wide range of aging temperature and aging time.

Long-Term Performance Benefits of the Design-Build Delivery Method Applied to Road Pavement Projects in the U.S.

The use of alternative project delivery methods has grown significantly over the last two decades. One such method is design-build (DB), which has been increasingly used due to its improved project cost and schedule performance. However, the project itself is only a fraction of the lifecycle of a built facility. Therefore, there is a need to understand whether delivery methods also impact the long-term performance of facilities. This paper focuses on quantifying the long-term performance impact of DB on pavements, compared to pavements delivered using the traditional design-bid-build (DBB) method. The international roughness index is selected as the metric to compare ride quality across projects. In total, the authors collected 9,946 data points representing 37 unique lane directions from 26 projects in six states, which they analyzed using linear mixed-effects methods. Results show that long-term performance of asphalt concrete pavement resurfacing DB projects is superior to that of comparable DBB projects by an equivalent of eight years of pavement life. A life cycle cost analysis shows the estimated monetary impact of these findings on the National Highway System is around $100 billion over the next 45 years.

Influence of Temperature Upon Permanent Deformation Parameters of Asphalt Concrete Mixes

The performance of asphalt concrete pavement has affected by many factors, the temperature is the most important environmental one which has a large effect on the structural behavior of flexible pavement materials. The main cause of premature failure of pavement is the rutting, Due to the viscoelastic nature of the asphalt cement, rutting is more pronounced in hot climate areas because the viscosity of the asphalt binder which isinversely related to rutting is significantly reduced with the increase in temperature resulting in a more rut susceptible paving mixtures. The objective of this study is to determine the effect of temperatures variations on the permanent deformation parameters (permanent strain (p), intercept (a), slope (b), Alpha and Mu) as well as resilient strain (r) and resilient modulus (Mr). To achieve this objective, one aggregate gradation with 12.5mm nominal maximum size, two grades of asphalt cements (40-50 and 60-70) brought form Al- Daurah refinery, limestone dust filler has been used to prepare the asphalt concrete mixtures. 30 Marshall specimens were prepared to determine the optimum asphalt cement content. Thereafter, 30 cylindrical asphalt concrete specimens (102mm in diameter and 203 mm in height) are prepared in optimum asphalt cement and optimum ±0.5 percent. The prepared specimens were used in uniaxial repeated load test to evaluate the permanent deformation parameters of asphalt concrete mixes under the following testing temperature (5, 15, 25, 40 and 60c). The test result analyses appeared that Mr is decrease 51 percent when temperature increased from 5 c to 25 c and then decrease 22 percent with further increase in temperature from 25 c to 60 c. Also, the Alpha value decreases by a factor of 1.25 and 1.13 when temperature increases from 5 c to 25 c and 25 c to 60 c, espectively. Finally, statistical models were developed to predict the Alpha and Mu parameters of permanent deformation.

A multiscale model for predicting the viscoelastic properties of asphalt concrete

It is well known that the accurate prediction of long term performance of asphalt concrete pavement requires modeling to account for viscoelasticity within the mastic. However, accounting for viscoelasticity can be costly when the material properties are measured at the scale of asphalt concrete. This is due to the fact that the material testing protocols must be performed recursively for each mixture considered for use in the final design. In this paper, a four level multiscale computational micromechanics methodology is utilized to determine the accuracy of micromechanics versus directly measured viscoelastic properties of asphalt concrete pavement. This is accomplished by first measuring the viscoelastic dynamic modulus of asphalt binder, as well as the elastic properties of the constituents, and this comprised the first scale analysis. In the second scale analysis, the finite element method is utilized to predict the effect of mineral fillers on the dynamic modulus. In the third scale analysis, the finite element method is again utilized to predict the effect of fine aggregates on the dynamic modulus. In the fourth and final scale analysis, the finite element method is utilized to predict the effect of large aggregates on the dynamic modulus of asphalt concrete. This final predicted result is then compared to the experimentally measured dynamic modulus of two different asphalt concretes for various volume fractions of the constituents. Results reveal that the errors in predictions are on the order of 60 %, while the ranking of the mixtures was consistent with experimental results. It should be noted that differences between the “final predicted results” and the experimental results can provide fruitful ground for understanding the effect of interactions not considered in the multiscale approach, most importantly, chemical interactions.

A mechanistic approach to evaluate the potential of the debonding distress in asphalt pavements

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.

Prediction models for fatigue resistance of local hot mix asphalt

The performance of asphalt concrete pavement depends on the bitumen properties, asphalt concrete mixtures, volumetric properties and external factors such as traffic volume and environment. Higher traffic volume produces high stress within pavement layer, which is one of the main causes for pavement distress. Fatigue cracking is considered to be the most important type of distress affecting the performance of asphalt concrete pavements on major state highways. This distress reduces the service life of the pavement and increases the maintenance cost. This paper describes the results of a laboratory study of the fatigue response of a typical asphalt concrete mixes to define the effects of degree of compaction (as measured by air-void content), asphalt content, temperature and ageing on the performance parameter. To achieve the objective of this research, the Nottingham flexural fatigue test is considered and super pave mix design requirements are employed. Test specimens (400 mm length by 63 mm width and 50 mm height) were sawed from slabs of the mixes prepared to the target air-void contents by rolling wheel compaction. Controlled-strain flexural fatigue tests were conducted using the Nottingham flexural fatigue test equipment and procedure. The tests were conducted at temperatures of 10 ± 1°C (50 ± 2°F), 20 ± 1°C (68 ± 2°F) and 30 ± 1°C (86 ± 2°F) and at a frequency of loading of 10 Hz. The long-term ageing experiment employed a full factorial design as well, with three asphalt contents, two ageing periods, two air-void contents and three test temperatures for a nominal total of 36 tests. Local material properties, stress-level and environmental impacts were considered for this aspect. In addition, field data are collected from different-aged pavement sections to check the applicability of fatigue prediction in the field through testing cores of (400 mm length × 300 mm width); laboratory results that are judged to be simulation of field compaction conditions were analysed. Fatigue life of hot mix asphalt and stiffness models for super-pave-compacted asphalt concrete wearing course mixtures were developed using statistical analyses by the aid of a software as a function of: degree of compaction (air-void content), temperature, ageing and asphalt content. Finally, a series of recommendations are presented for enhancing the fatigue performance of pavements, including changes to current construction quality assurance procedures.

하모니 검색 알고리즘을 이용한 피로균열의 포장설계 및 유지보수 시기 결정

PURPOSES : This research describes how to predict the life cycles of fatigue cracking based on NCHRP Report 704 as well as modified harmony search (MHS) algorithm. METHODS : The fatigue cracking regression model of NCHRP Report 704 was used in order to calculate the ESAL (Equivalent Single Axle Load) numbers up to pavement failure, based on using material parameters, composite modulus, and surface pavement thickness. Furthermore, the MHS algorithm was implemented to find appropriate material parameters and other structural conditions given the number of ESALs, which is related to pavement service life. RESULTS : The case studies show that the material and structural parameters can be obtained, resulting in satisfying the failure endurance of asphalt concrete structure, given the number of ESALs. For example, the required ESALs such as one or two millions are targeted to satisfy the service performance of asphalt concrete pavements in this study. CONCLUSIONS : According to the case studies, It can be concluded that the MHS algorithm provides a good tool of optimization problems in terms of minimizing the difference between the required service cycles, which is a given value, and the calculated service cycles, which is obtained from the fatigue cracking regression model.

The changes in the mechanical properties of neat and SBS-modified HMA pavements due to traffic loads and environmental effects over a one-year period

There is a great need for an extensive examination of the performance of asphalt concrete pavements which is made from hot mix asphalt (HMA) since recently there has been an increasing need for roads to parallel the increase in the number of vehicles on the roads. The present study focuses on determining experimentally and numerically the changes in the mechanical properties of neat and SBS modified asphalt mixes exposed to traffic loads and environmental effects over a one-year period. In order to achieve this purpose, in the first part of the experimental study, conventional asphalt tests were carried out in relation to the aggregate and bitumen constituting neat and SBS modified HMAs, and the physical properties of the materials used in HMA were determined and compared to the limits of the related specifications, so that their compatibility to the standards were examined. In the second part of the experimental study, 48 core samples for 4 sample types (NK, NT, SK and ST) were collected from the road side and the vehicle wheel passing line of the asphalt concrete pavement was produced by using neat and SBS modified HMA at specific times over a one-year period and they were examined with Marshall stability-flow tests and performance test; thus, their mechanical properties were determined. In the numerical analysis part of the study, the analyses of 16 models made for 4 sample types were done via Abaqus CAE finite element software, and the changes in the material behaviour under traffic loads and environmental effects over the course of one year was obtained in terms of Von Mises stresses and the data obtained was compared with the experimental data. Finally, the stress-time and ITSM-time relationships for the four sample types were determined via the regression analysis method. The results of the research have revealed that there had been considerable changes in the mechanical properties of the neat and SBS modified asphalt mixture samples, taken at specific times over a one-year period, because of the traffic loads and environmental effects.

Development of a rutting performance model for asphalt concrete pavement based on test road and accelerated pavement test data

This paper describes the development of a model for estimating the rutting performance of asphalt concrete pavement (HMA: dense grade) under various temperatures and loads. The model was developed using both Accelerated Pavement Testing (APT) and test road measurements. APT parameters were selected to match test road conditions (including asphalt structure, traffic load, and temperature) as closely as possible. The temperatures used were 33, 40, and 50°C, and the loads ranged from 41.2 to 80.4-kN (converted to equivalent single-axle loads for comparison to test road data). The results were used for developing a rutting model with temperature and the number of standard axle loads as the variables. The APT model was then used for estimating the cumulative load and the rutting depth on the test road under field conditions. The model estimates were compared with actual test road measurements, and a final model was calibrated using field data.

Improved method of considering air void and asphalt content changes on long-term performance of asphalt concrete pavements

Mixture properties (aggregate gradation and volumetric quantities), rate of loading and environmental conditions are the most important factors that affect the |E*| values. The main objective of this study was to develop a rational approach to investigate and model the effect of air voids and asphalt content on the |E*| master curves and consequently predict pavement performance. In this study, |E*| tests were conducted on three asphalt concrete mixtures with the same aggregate gradation, but different binder grades. For each of these mixtures, the air void and asphalt contents were varied at three levels. It is found that the developed method provides a more accurate estimate of the effects of volumetric changes in hot mix asphalt. The application of the proposed approach would be most beneficial for quality control/quality assurance purposes, performance-related specifications and for estimating contractors' incentives and penalties, where |E*| is utilised to predict the pavement performance.

Effects of Oxidative Aging on Asphalt Mixture Properties

Aging has long been recognized as a contributing factor to fatigue distress of asphalt concrete pavement. Several research studies have been undertaken to gain fundamental understanding of the aging phenomenon at the asphalt binder level. However, relatively little effort has been made to understand and to quantify the effects of aging on fundamental characteristics of asphalt mixtures. The effects of oxidative aging on the dynamic modulus and the fatigue performance of asphalt mixtures is examined. For this purpose, an asphalt mixture is aged in the laboratory at four aging levels. Mechanical tests for the four aged mixtures are performed to characterize the linear viscoelastic and damage properties. Such characterization is investigated to incorporate the aging effects into a more comprehensive analytical framework for predicting the performance of asphalt concrete pavements. Finally, this framework is used to evaluate the aging effects on an example asphalt concrete pavement. It is found that aging can significantly change the performance of an asphalt concrete pavement, depending on the location evaluated within the pavement structure as well as climate conditions.