Types Of Asphalt Mixtures Research Articles

Flexible pavement thermal cracking performance sensitivity to fracture energy variation of asphalt mixtures

Thermal cracking in asphalt pavements continues to be a significant pavement distress mechanism in cold climate regions. The formation of discontinuities due to thermal cracking causes extensive damage to the integrity of the pavement and forms pathways for intrusion of water into the base and subgrade layers. Current use of the performance-based binder specifications has not been shown to effectively lower the propensity for this distress. When this is combined with advent of newer asphalt mix manufacturing and construction technologies as well as desire for incorporation of greater amounts of recycled materials in paving mixtures, it has led to significant research and implementation efforts on asphalt mixture performance-based specifications. On the basis of various past research studies on low temperature cracking, a performance specification that utilises fracture energy of asphalt mixtures through use of disk-shaped compact tension (DCT) test has been developed. A significant number of present studies are underway to implement these specifications including two states which are in the pilot implementation stage. A major question that has been raised during the implementation of these specifications has been in the lack of information on sensitivity of pavement thermal cracking performance to the variations in fracture energy of the mixture. The present study focused on determining the effects on thermal cracking performance of pavements for variations in DCT fracture energy of asphalt mixtures. The sensitivity was determined through use of the IlliTC thermal cracking simulation system. The IlliTC system utilises asphalt mixture's fracture and viscoelastic properties to conduct finite element-based simulations using realistic pavement thermal loading conditions. Although this system has been validated in the past, the present study conducted further validation through comparison of predicted cracking performance with field-measured cracking performance. For sensitivity analysis, three types of asphalt mixtures for three climatic conditions and three pavement structures were evaluated. Apart from other things, the fracture mechanics in asphalt concrete at lower temperatures depend on the material's fracture energy as well as its tensile strength. In order to ensure that the effects of fracture energy variations were the focus, a critical tensile strength value was determined for each scenario (for each mix for each climate), which allowed researchers to conduct the simulations with varying fracture energies (six different levels). The results show that a variation of 25 J/m2 in the fracture energy could lead to significantly different pavement thermal cracking performances. This is a significant finding that will aid in continued implementation of the fracture energy-based material specifications and provides guidance to transportation agencies in development of the final version of their material specifications.

High-temperature failure in asphalt mixtures using micro-structural investigation and image analysis

In this study, evaluating the effect of internal structure in asphalt mixture on high-temperature deformation is the main objective. Three asphalt mixture types, dense-graded asphalt concrete, superpave and stone mastic asphalt, which widely used as pavement were selected to investigate the internal structure at meso-scale level. The internal microstructures were established by X-ray computed tomography data, and three-dimensional models were processed by digital image processing technology. Adaptive threshold segmentation algorithm based on annular regions was improved, and then utilized to extract aggregates and air-voids from gray image. Meanwhile, the morphology and distribution of air-voids and aggregates were measured. Results indicate that the improved image segmentation algorithm segregates the target and background effectively. Air-voids can be extended into a macro cracks mainly because of the horizontal shear damage, but air-voids nearby the load action area are compressed and eliminated. The content and size of coarse aggregates have an obvious influence on high-temperature failure, compressive region and shear rheological region can be divided due to the different failure mechanism. Moreover, it is found that the position changes which horizontal displacement greater than vertical displacement of aggregate particles mainly appears in shear rheological region. The method developed in this paper is an effective tool to study high-temperature failure mechanisms of asphalt mixture.

Estimation of phase angles of asphalt mixtures using resilient modulus test

The main objective of this study was to develop, derive, and estimate the phase angle (ϕ) parameter from resilient modulus (Mr) test, designated ϕMr, at various temperatures and frequencies for eleven types of asphalt mixtures: two conventional dense-graded (DGAC), four polymer-modified gap-graded (P-Gap), four asphalt–rubber gap-graded (AR-Gap), and one asphalt–rubber open-graded (AR-Open) mix. ϕMr were estimated for the eleven mixes with three replicates per mix totalling 33 samples at 15, 25 and 35°C and at 0.5, 1, and 1.5Hz. AR-Open mixes had the highest ϕMr followed by AR-Gap and P-Gap, and then followed by DGAC mixes. Principally, with an increase in the asphalt content from conventional to modified mixes, there was an increase in ϕMr, suggestive of the fact that the mixes that had higher asphalt contents have extra-viscous response or are highly viscoelastic. Furthermore, ϕMr predictive model was developed based on asphalt material properties totalling 99 data points provided by R2adj (adjusted coefficient of estimation)=0.8390, and Se/Sy (ratio of standard error to standard deviation indicative of relative accuracy of the predictive model)=0.3820; depicting very good correlation between the estimated and predicted ϕMr, and with low bias and high precision. Additionally, ϕMr master curves were constructed for the mixes with 35°C as reference. Overall, it is envisioned that ϕMr parameter obtained in this study will be helpful to comprehensively understand the viscoelastic properties of different asphalt mixtures, and incorporate ϕMr as a viscoelastic characteristic assessor in futuristic flexible pavement designs.

Method for Predicting the Laboratory Compaction Behavior of Asphalt Mixtures

AbstractThe quality of compaction significantly influences the performance of asphalt mixtures. Insufficient compaction often leads to excessive premature permanent deformation, excessive aging, and/or moisture damage. The research reported in this paper was aimed at developing a prediction model for laboratory compaction of asphalt mixtures. The model was developed based on extensive laboratory measurements and it includes parameters that describe aggregate shape characteristics, aggregate gradation, and binder content. The results show that the asphalt mixture type, aggregate properties, and binder content have a significant effect on the slope and intercept values of the laboratory compaction curves. Two models that describe both the slope and intercept of the laboratory compaction curves of asphalt mixtures are presented. These models provide valuable inputs that can be used to quantify the compaction effort needed to compact asphalt mixtures in the laboratory and correlate this effort to field compac...

Representative volume element of asphalt pavement for electromagnetic measurements

The motivation for this study was to investigate the representative volume element (RVE) needed to correlate the nondestructive electromagnetic (EM) measurements with the conventional destructive asphalt pavement quality control measurements. A large pavement rehabilitation contract was used as the test site for the experiment. Pavement cores were drilled from the same locations where the stationary and continuous Ground Penetrating Radar (GPR) measurements were obtained. Laboratory measurements included testing the bulk density of cores using two methods, the surface-saturated dry method and determining bulk density by dimensions. Also, Vector Network Analyzer (VNA) and the through specimen transmission configuration were employed at microwave frequencies to measure the reference dielectric constant of cores using two different footprint areas and therefore volume elements. The RVE for EM measurements turns out to be frequency dependent; therefore in addition to being dependent on asphalt mixture type and method of obtaining bulk density, it is dependent on the resolution of the EM method used. Then, although the average bulk property results agreed with theoretical formulations of higher core air void content giving a lower dielectric constant, for the individual cores there was no correlation for the VNA measurements because the volume element seizes deviated. Similarly, GPR technique was unable to capture the spatial variation of pavement air voids measured from the 150-mm drill cores. More research is needed to determine the usable RVE for asphalt.

Use of the Resilient Modulus Test to Characterize Asphalt Mixtures with Recycled Materials and Recycling Agents

Asphalt mixture stiffness is an important parameter used during pavement design and the evaluation of pavement performance. This study used the resilient modulus ( MR) test (ASTM D7369) to measure the stiffness of several types of asphalt mixtures and various specimen types. Five types of asphalt mixtures were studied: virgin mixture without recycled materials; control mixture with recycled asphalt pavement (RAP), recycled asphalt shingles (RAS), and warm-mix asphalt additive; and three other mixtures with RAP, RAS, and different types of recycling agents. The specimen types used in the study were field cores, on-site plant mix laboratory-compacted specimens, and reheated plant mix laboratory-compacted specimens. The objectives of the study were to assess the effect on MR values of ( a) smoothness of field core surfaces and ( b) measurement angle in field cores and laboratory-compacted specimens. In addition, the study compared the MR results for the various mixture and specimen types. The results indicated that smoothness and measurement angle had no statistically significant effect on MR at the 95% confidence level. However, the test was able to identify statistically significant differences between mixture and specimen types. Finally, a comparison between MR and dynamic modulus (DM) test (AASHTO TP79) results showed equivalent ranking of the mixtures, confirming that MR is a practical alternative to DM testing.

Rheological Properties of Asphalt Mixtures for Bridge Pavements

This paper presents the laboratory test results of rheological properties of asphalt mixtures for bridge pavements. The research plan included typically used asphalt mixtures - asphalt concrete (AC) and stone mastic asphalt (SMA). A new type of mixtures, SMA-MA, were also tested. These mixtures were tested for their stiffness in different temperatures and varied frequencies. The following parameters were identified - dynamic modulus and phase angle. The results of this research proved that these types of asphalt mixtures affect the viscoelastic properties and durability of bridge pavements.

Evaluation of a permanent deformation model for asphalt concrete mixtures using extra-large wheel-tracking and heavy vehicle simulator tests

This paper evaluates a mechanistic–empirical permanent strain model for asphalt concrete mixtures. The evaluation was carried out based on two different types of tests: an extra-large wheel-tracking (ELWT) test and a full-scale accelerated pavement test using a heavy vehicle simulator (HVS). Asphalt slabs from three different types of asphalt mixtures were prepared for the ELWT test and tested at several pavement temperatures and tyre inflation pressures. Lateral wandering was also incorporated. The measured permanent deformations in the asphalt slabs were thereafter modelled using the permanent strain model from the US Mechanistic-Empirical Pavement Design Guide and model parameters were estimated for the three types of mixes. For validation, data from an HVS tested pavement structure consisting of the same asphalt mixtures as those tested using the ELWT were used. A set of calibration factors for the three mixtures were therefore obtained between the two tests. In all cases, the calibration factors were within ±20% from unity. Differences in geometry, scale, wheel loading configuration as well as the speed of loading between the two test devices could be the possible reasons for the differences in observed calibration factors.

Using energy parameters based on the surface free energy concept to evaluate the moisture susceptibility of hot mix asphalt

Although the conventional laboratory test procedure is helpful in comparative analysis of moisture susceptibility of hot mix asphalt (HMA), it does not focus on measuring the fundamental material properties related to the mechanisms of moisture damage. In this study, comparing results of tensile strength ratio test and surface free energy method resulted in the determination of important energy parameters that can be employed as a quantitative indicator to assess moisture susceptibility of HMA. Three of the four parameters used in this research have a convenient correlation with the laboratory results. The ratio of the difference between the surface adhesion of asphalt–aggregate and the water–aggregate to the surface adhesion of the asphalt–aggregate (EP1) had the best correlation with the tensile strength ratio of 32 types of asphalt mixtures. This parameter can be used as a tool for moisture sensitivity detection with more caution. Also, the ratio of the surface energy of adhesion of the asphalt–aggregate to the difference between the surface energy of adhesion in dry and wet conditions (EP2) had good correlation with laboratory results.

Use of Imaging Techniques for Viewing the Internal Structure of Rubberised Asphalt Mixtures

This paper presents the application of different imaging techniques for viewing the internal structure of rubberized asphalt mixture as road materials. Two imaging techniques were used to capture the internal structure images of its compacted samples i.e. X-ray Computed Tomography (non-destructive method) and Scanning Electron Microscope, SEM (destructive method). Since a lot of previous researchers have produced extensive works on the mechanical properties, therefore, this study is an attempt to introduce the microstructure of rubberized asphalt mixtures produced using dry process method. Two types of dry mixed rubberized asphalt mixture were prepared by modifying a Hot Rolled Asphalt Mixture (HRA 60/20) with different crumb rubber sizes. A mixture of conventional HRA 60/20 was also scanned for comparison. The illustrations are aimed to provide the researchers more information regarding their internal structure distribution.Keywords: Imaging techniques, X-ray Computed Tomography, Scanning Electron Microscope, Rubberised Asphalt Mixture

LOW-NOISE PAVEMENT AS A WAY OF LIMITATION OF TRAFFIC NOISE LEVEL

Road surface can significantly reduce the traffic noise level. Depending on the characteristic of the upper surface layers the differences between the maximum rolling noise levels from passing vehicles to reach values about 10 dB (A). A special group is low-noise pavements characterized by the presence of voids above 15%. Application the porous asphalt layers or asphalt mixture type BBTM affects a significant reduction the width of land surrounded the roads where permissible equivalent sound level is exceeded. Such solutions in some cases can replace acoustic barriers. Road pavements with a higher content of voids require proper maintenance because their acoustic performances are reduced during operation.

Renovated Comprehensive Multilevel Evaluation Approach to Self-Healing of Asphalt Mixtures

AbstractBased on fuzzy evaluation and the analysis hierarchy process, this paper develops a method for evaluating the self-healing capability of asphalt mixtures. In developing the method, 18 judgment indicators were selected on the basis of a study on the influence factors of self-healing capability, and a numerical approach was established to describe the properties of these indicators. Four types of subordinate functions with 16 mathematical expressions were set up to describe the properties of the continuous indicators, and empirical approaches were used to deal with the dispersion indicators. Based on the improved analysis hierarchy process, a renovated comprehensive multilevel evaluation method was developed to evaluate the self-healing capability of asphalt mixtures. Finally, the feasibility and effectiveness of the method were validated with excellent results using a type of asphalt mixture from engineering practice.

Influence of Intermediate Course Gradation Type on Anti-Fatigue Performance of the Asphalt Pavement Structure

Three grading types of asphalt mixture are designed and respectively placed in intermediate course of asphalt concrete pavement with a typical semi-rigid base layer, the pavement structure model is established by the application of finite element software, the tensile stress at the bottom of intermediate course is analyzed under the wheel pressure of 1.5MPa, the finite element calculation results are led to the fatigue analysis software nSoft, the fatigue analysis results of intermediate course materials are obtained. The results show that the design gradation AC-20 mixture has excellent fatigue resistance in the pavement structure layer.

Fatigue property of basalt fiber-modified asphalt mixture under complicated environment

The fatigue property of asphalt mixtures under complicated environment (low-temperature bending performance, chloride penetration, freezing-thawing cycle and their coupling effect) and the improvement effect for relevant property of basalt fiber-reinforcing asphalt mixture under complicated environment are studied. Two grading types of asphalt mixtures, AC-16I and AC-13I, are chosen, whose optimum asphalt-aggregate ratio and optimum dosage of basalt fiber are determined by the Marshall test. The standard specimens are made firstly, and then the low temperature bending tests of asphalt mixture and basalt fiber-reinforced asphalt mixture under the coupling effect of the chloride erosion and freezing-thawing cycle have been carried out. Finally, the fatigue property tests of asphalt mixture and basalt fiber-reinforced asphalt mixture under complex environment are performed on MTS material testing system. The results indicate that the tensile strength, the maximum curving tensile stress, the curving stiffness modulus, and fatigue properties of asphalt mixture are influenced by the coupling effect of the chloride erosion and freezing-thawing cycle. The low-temperature bending performance and fatigue property of asphalt mixtures under complicated environment can be greatly improved by adding moderate basalt fiber. The dense gradation asphalt mixture possesses stronger ability to resist adverse environmental effects under the same condition.

Investigation on the Properties of Asphalt Mixtures Containing Antifreeze Fillers

AbstractTo investigate the properties of antifreeze asphalt mixtures (AFAC), the dense-graded and gap-graded asphalt mixtures, AC-13 and SMA-13, containing 2, 4, 5, 6, and 4 % by weight and 5, 6, 7, and 8 % by weight antifreeze filler, respectively, were used in this paper. In the experiments, Marshall, rutting, bending beam, and immersion Marshall tests were used to study the engineering performances of AFAC. In addition, a conductivity test was carried out to evaluate the salt releasing law under static state condition. Results show that the properties of AFAC are affected by the gradation composition and content of antifreeze filler. It is suggested that the content of antifreeze filler is 3∼6% by weight according to the Marshall test. The composition type of asphalt mixture is an important factor in AFAC because the durability of SMA-13 is worse than that of AC-13. Moreover, the salt releasing process is divided into three steps based on the conductivity test.

Rheological Properties of Asphalt Mixtures with Additives Based on Renewable Sources

The deformational properties and fatigue of asphalt layers are important for the design and assessment of semi-rigid and flexible pavements. The Two-point Bending Test was used for determination of deformational characteristics of asphalt mixtures on Department of Construction Management in Žilina. The results are evaluated with the KATEMS assessment software. The long-term research leads to estimation of deformational characteristics and fatigue of different types of asphalt mixtures. The tests have shown a positive impact of additives (ground rubber, hydrate lime component, recycling materials,...) on the results of these mixtures. This article is focused on assessment of deformational properties and fatigue of selected types of asphalt mixtures, there are viscoelastic materials in construction of pavement.

Grey Relational Analysis of Fiber Asphalt Mixture Based on Pavement Performance and Economic Benefits

In order to explore performance and economic benefits of the most commonly used fiber asphalt mixture, four types of fiber asphalt mixture were studied in this paper through a series of capability tests, such as water stability, high stability, low temperature crack resistance and fatigue stability test. Based on dynamic stability, low temperature bending strain, freeze-thaw splitting strength ratio, fatigue life and cost per square meter as the evaluation index, Grey Relational Analysis (GRA) was proposed in this study to determine the best performance and economic benefits of fiber asphalt mixture. The results show that Fiber B asphalt mixture only has better anti-cracking performance in low temperature and fatigue life,but fiber C asphalt mixture has better performance and economy than the other three fiber asphalt mixtures under the same conditions with grey relational analysis.

Additive Percent Influence on “Warm Mix” Behavior

Abstract The benefits of WMA technologies include reduced fuel usage and emissions in support of sustainable development, improved field compaction, which can facilitate longer haul distances and cool weather pavement, and better working conditions. Since this is a relatively new technology, it is necessary to determine the behavior and the performances of this type of asphalt mixture depending on additive percent. These technologies tend to reduce the viscosity of the asphalt and provide for the complete coating of aggregates at lower temperatures. WMA is produced at temperatures 20 to 30°C lower than typical hot-mix asphalt (HMA). The paper presents the results obtained in the Road Laboratory of Technical University of Civil Engineering Bucharest on an asphalt mixture with fibers (MASF16) prepared according to the “warm mix” technology with chemical additive. Different percent of additive are used in laboratory to draw up the “master curves” of asphalt mixture obtained by 4PB-PR stiffness modulus results.

Rheology, Deformational Properties and Fatigue of the Asphalt Mixtures

The deformational properties and fatigue of asphalt layers are important for the design and assessment of semi-rigid and flexible pavements. The Two-point Bending Test was used for determination of deformational characteristics of asphalt mixtures on Department of Construction Management in Zilina. The results are evaluated with the KATEMS assessment software. The long-term research lead to estimation of deformational characteristics and fatigue of different types of asphalt mixtures. The tests have shown a positive impact of additives (ground rubber, hydrate lime component) on the results of these mixtures. This article is focused on assessment of deformational properties and fatigue of selected types of asphalt mixtures.

Novel Method for Moisture Susceptibility and Rutting Evaluation Using Hamburg Wheel Tracking Test

The Hamburg wheel tracking test (HWTT) has been widely used as a standard laboratory test to evaluate the moisture susceptibility and rutting resistance of asphalt mixtures. The stripping infection point and the rut depth at a certain number of load cycles are two common parameters obtained from the test. Although these parameters have been widely adopted by several transportation agencies, the accuracy and variability in characterizing mixture properties of these parameters have been questioned. In this study, a novel method to analyze the HWTT results is introduced and three new parameters are proposed to measure the moisture susceptibility and rutting resistance of asphalt mixtures. The new parameters are compared against the current ones to assess their capability to discriminate between three types of asphalt mixtures with different performance results in the HWTT. Significant advantages in characterizing mixture resistance to stripping and rutting are demonstrated by the new parameters. In addition, the effect of antistripping additives and recycled materials on mixture performance in the HWTT is evaluated with mixtures from a field project in Texas. Test results for the new parameters show that the addition of antistripping additives improves the susceptibility of asphalt mixtures to moisture. Specifically, the use of lime is more beneficial for improving mixture performance than a liquid antistripping agent. Conversely, the addition of recycled materials provides mixtures with increased moisture susceptibility but improved rutting resistance.