High Modulus Asphalt Concrete Research Articles

Temperature effect on fatigue behavior of high-modulus asphalt concrete (HMAC)

This study investigated the effect of temperature on the fatigue behavior of high-modulus asphalt concrete (HMAC). The impact of temperature on the Wöhler’s curve parameters, especially with respect to the slope and intercept, was studied to evaluate the accuracy of current methodologies used to estimate them in mechanistic–empirical pavement design tools (M-E PD). Four series of tension–compression (TC) fatigue tests were conducted on HMAC samples at four temperatures (-8.3 °C, 1.4 °C, 11.3 °C, and 21.0 °C). The findings indicated a significant impact of temperature on the intercept; the slope did not exhibit any statistically significant effect.

Development and Analysis of High-Modulus Asphalt Concrete Predictive Model

The main purpose of this paper is to present the development of a new predictive model intended for the calculation of stiffness modulus |E*| determined by a four-point bending beam test (4PBB or 4PB-PR). The model developed, called model A, was based on the Witczak model, which was developed for the dynamic-modulus (DM) method. Most of the asphalt mixtures used to develop the model were high-modulus asphalt concrete (HMAC). The most commonly used methods for determining the stiffness modulus |E*| of asphalt mixtures were also discussed. The paper presents the results of the study for 10 asphalt mixtures but 8 of them were used to develop the predictive model. In addition, the results of complex shear modulus G* tests on neat and modified bituminous binders carried out in a dynamic shear rheometer (DSR), necessary for the development of a predictive model, are presented. The tests carried out in the dynamic shear rheometer had significant measurement uncertainties. The results of the volumetric parameters of the asphalt mixtures are also reported. The developed model A has maximum absolute errors e = 1930 MPa (p = 95%) and maximum relative errors re = 50% (p = 95%). The distribution of the absolute errors of the model, after discarding outliers, has a normal distribution as in the development of other models of this type, which was confirmed by appropriate statistical tests. On the basis of the tests and calculations carried out, it was concluded that, in order to increase the precision of the predictive models, it is advisable to reduce the measurement uncertainty of the bitumen complex shear modulus G*. For the developed model A, the limiting values of the stiffness modulus |E*| are also shown, within which the determined stiffness modulus should fall.

On the Use of Recycled Asphalt and Trinidad Lake Asphalt (TLA) for the Preparation of High Modulus Asphalt Concrete

Rutting of asphalt pavement occurs earlier and is more serious under the increasingly heavy traffic load conditions that can be found in subtropical monsoon climate regions. High modulus asphalt concrete (HMAC) with excellent anti-rutting and anti-fatigue properties is generally used to mitigate this issue. Given the relatively high cost of the additives used in this type of asphalt, in this study the feasibility of using recycled asphalt mixture (RAP) and Trinidad lake asphalt (TLA) for the preparation of HMAC is considered. The mineral composition of the RAP is first analyzed, then the TLA modified asphalt with different levels of RAP content is used to assess the effect of RAP on the performance of the mixture. Finally, the high-temperature rheological properties of extracted bitumen and the adhesion characteristic between mineral and bitumen are analyzed. The results show that after RAP combustion, the yellowish and greyish minerals display different alkalinity values, while the greyish mineral exhibits an improved ability to combine with bitumen. Thus, RAP can significantly enhance the high-temperature rutting resistance of TLA modified asphalt mixtures. The aged bitumen in RAP makes the mixed binder harder and improves its rheological properties at high temperatures.

Using Phenol Formaldehyde Resin, Hexamethylenetetramine and Matrix Asphalt to Synthesize Hard-Grade Asphalts for High-Modulus Asphalt Concrete

Traditional hard-grade asphalts for high-modulus asphalt concrete (HMAC) are produced by using natural hard-grade asphalt to modify matrix asphalts. However, natural hard-grade asphalts are scarce and expensive. To find a sustainable alternative, this study presented a method to synthesize hard-grade asphalts using phenol formaldehyde resin (PFR), hexamethylenetetramine (HMTA) and matrix asphalts. Infrared radiation (IR) spectra analysis and fraction analysis for the modifiers and synthesize asphalts show that asphalt molecules can be cross-linked into larger polymeric groups by the thermosetting phenol formaldehyde resin (TPFR) which is the reaction product of PFR and HMTA. This process increased the asphaltene and resin fraction in asphalt, thus transforming a matrix asphalt into hard grade. With the dosing combinations of 4% PFR/15~20% HMTA, 6% PFR/8~10% HMTA and 8% PFR/5~5.7% HMTA, dynamic modules of HMAC were 14,000~16,000 MPa, which satisfied the basic application requirements for HMAC. The rutting resistance of the new hard-grade asphalts with the above dosage combinations completely exceeds the traditional product using the Trinidad Lake asphalt as the raw material. Increasing the amount of PFR/HMTA can further improve the rutting resistance. However, to ensure the fatigue and cracking resistance of the HMAC can get a level like the traditional product, the dosages of HMTA should be controlled below 15%.

Validation of time temperature superposition principle for high modulus asphalt concrete in the linear viscoelastic and fatigue domains

AbstractValidation of time–temperature superposition principle (TTSP) in the fatigue domain for a high modulus asphalt concrete (HMAC) is presented in this paper. All tests were performed in tension‐compression under strain control mode. First, TTSP was validated in the linear viscoelastic domain. Then, fatigue tests were performed under three loading conditions, 9.2°C and 5 Hz, 11.0°C and 10 Hz and 12.9°C and 20 Hz, which are equivalent regarding TTSP. Two fatigue protocols were adopted: continuous fatigue test (FT) and fatigue test with rest period (FTRP). For FT, three samples were tested at 180μm/m for each loading condition whereas for FTRP, one sample was tested at 100 μm/m. The data were analysed by comparing the dynamic modulus evolution as a function of time or the fatigue life duration. The results showed that HMAC with fatigue damage remains thermorheologically simple (i.e., respects the TTSP) in the studied temperatures range.

Laboratory Evaluation of Dynamic Characteristics of a New High-Modulus Asphalt Mixture

With the rapid increase in traffic volume and heavy-duty vehicles, rutting has become one of the most serious problems threatening the service quality and life of asphalt pavement. High-modulus asphalt concrete is a promising method to overcome this problem, contributing to the sustainable development of asphalt pavement. In this study, a new composite high-modulus agent (CHMA)-modified asphalt binder and mixture were prepared, and their dynamic mechanical characteristics were investigated by the dynamic shear rheometer, dynamic modulus test, wheel tracking test, frequency sweep test at a constant height (FSCH), and repeated shear test at a constant height (RSCH) to comprehensively evaluate its high-temperature stability. Test results showed that the rheological property of the CHMA-modified asphalt binder was similar to that of low-graded asphalt binder, implying that it had a strong potential in resisting deformation. The dynamic modulus of AC-20(CHMA) was 19,568 MPa at 15 °C and 10 Hz condition, meeting the requirement for the high-modulus asphalt mixture (higher than 14,000 MPa). The dynamic stability of AC-20(CHMA) was 8094 times/mm, lower than that of AC-20(20#), but remarkably higher than that of AC-20(SBS). AC-20(20#) and AC-20(CHMA) both showed strong shear resistance according to the FSCH test results. Under the repeated shear loadings, the growth rate of the shear strain increased rapidly in the primary stage, and then slowed down gradually, finally reaching a constant growth rate. The shear slope of AC-20(CHMA) was between that of AC-20(20#) and AC-20(SBS), demonstrating that its resistance to repeated shear loadings was superior to AC-20(SBS), although slightly weaker than AC-20(20#). The findings in this study provide references for alleviating rutting problems and improving the lifespan of asphalt pavement.

Unified characterizing fatigue performance of high modulus asphalt concretes under diverse stress state

As a new material, high modulus asphalt concrete (HMAC) with good durability is widely used in the pavement engineering. One of the most critical performance indexes of HMAC is the fatigue cracking. However, in the experiment of evaluating the fatigue properties, different anti-fatigue effects are obtained only by adding different modifiers. In addition, using only one loading mode to determine the fatigue properties of HMAC neglects the fact that there is a difference among the fatigue test results in various loading modes, which artificially leads to the non-uniqueness and unscientific design of high modulus asphalt pavements for the fatigue resistance. Therefore, four internationally accepted mainstream strength tests at different loading rates, including direct tension, indirect tension, unconfined compression and four-point bending tests, were carried out to enhance the veracity of structural resistance design of high modulus asphalt pavements. It is revealed that the fitted curve for the variation of strength with loading rate is a power function with velocity dependence, and the models for direct tension, indirect tension, unconfined compression, and four-point bending strengths established as a function of loading rate are SD = 3.218v0.1425, ST = 3.833v0.1768, SC = 14.391v0.1130 and SF = 7.839v0.1489 respectively. Besides, it is shown that the conventional S-N fatigue equation does not take into account the velocity dependence of the strength of HMAC in the stress ratios determined by the tests, and the velocity-dependent stress ratios defined in this paper are determined by the strength model and therefore take into account the viscoelasticity of HMAC. In addition, it is found that extending the fatigue curve backwards, when the fatigue life of HMAC is also close to 1, the velocity-dependent stress ratio is 1. Meanwhile, the fatigue model Nf = tv-5.318 was developed by unifying the characterization of HMAC and considering the effect of loading rate in various loading modes. It eliminated the difference of fatigue test results caused by the specimen sizes and loading modes, and effectively improved the completeness of structural design of high modulus asphalt pavements, which provided a theoretical basis for designing the high modulus asphalt pavements.

Development of Cost-Effective High-Modulus Asphalt Concrete Mixtures Using Crumb Rubber and Local Construction Materials in Louisiana

One of the emerging solutions to enhance the durability of asphalt pavements is the use of a French asphalt mix known as “High-Modulus Asphalt Concrete (HMAC).” This mix uses a hard asphalt binder, high binder content (about 6%), and low air voids content as compared with Superpave mixtures. The key objective of this study was to develop a cost-effective HMAC mixture using crumb rubber and local materials in Louisiana. To achieve this objective, four HMAC mixtures were prepared using two asphalt binders (PG 82-22 and PG 76-22 plus 10% crumb rubber) and two Reclaimed Asphalt Pavement (RAP) contents (20% and 40%); additionally, a conventional Superpave mixture in Louisiana was prepared as a control mixture. The laboratory performance of these five mixtures was evaluated in relation to workability, dynamic modulus, rutting resistance, and cracking resistance. The AASHTOWare Pavement ME Design software was also used to estimate the long-term field performance of these mixtures. Results indicated that the HMAC mixture prepared with 10% crumb rubber and 20% RAP successfully met the French mix design specifications for HMAC and LaDOTD specifications. This HMAC mix outperformed the control Superpave mix in relation to dynamic modulus, rutting resistance, and cracking resistance. Additionally, this HMAC mixture can reduce the required asphalt thickness by 1.5 or 2 in. based on traffic level. The cost-effectiveness analysis indicated that this HMAC mixture was more cost-effective than conventional Superpave mixtures in Louisiana. In addition, this mixture is environmentally friendly as it can reduce the disposal of scrap tires in landfills.

Field Evaluation of High Modulus Asphalt Concrete Resistance to Low-Temperature Cracking

High-modulus asphalt concrete has numerous advantages in comparison to conventional asphalt concrete, including increased resistance to permanent deformations and increased pavement fatigue life. However, previous studies have shown that the construction of road pavements with High Modulus Asphalt Concrete (HMAC) may significantly increase the risk of low-temperature cracking. Those observations were the motivation for the research presented in this paper. Four test sections with HMAC used in base and binder courses were evaluated in the study. Field investigations of the number of low-temperature cracks were performed over several years. It was established that the number of new low-temperature cracks is susceptible to many random factors, and the statistical term “reversion to the mean” should be considered. A new factor named Increase in Cracking Index was developed to analyze the resistance of pavement to low-temperature cracking. For all the considered field sections, samples were cut from each asphalt layer, and Thermal Stress Restrained Specimen Tests were performed in the laboratory. Correlations of temperature at failure and cryogenic stresses with the cracking intensity observed in the field were analyzed. The paper provides practical suggestions for pavement designers. When the use of high modulus asphalt concrete is planned for binder course and asphalt base, which may result in lower resistance to low-temperature cracking of pavement than in the case of conventional asphalt concrete, it is advisable to apply a wearing course with improved resistance to low-temperature cracking. Such an approach may compensate for the adverse effects of usage of high modulus asphalt concrete.

Determination of Minimum Dynamic Modulus (E*) of High Modulus Asphalt Concrete Applied to Semirigid Base Asphalt Pavement

AbstractIn order to mitigate the serious rutting disease of the semirigid base asphalt pavement (SBAP), measuring the settings of a high modulus asphalt concrete (HMAC) layer in the SBAP structure ...

Rheological behavior of high modulus asphalt binder and its indication for fracture performances

High modulus asphalt concrete (HMAC) has been used as a high-quality road construction material to tackle permanent deformation of asphalt mixtures primarily due to its exceedingly high modulus. However, rheological behavior, especially non-linear rheological behavior, and fracture behavior of high modulus asphalt binder (HMAB) are not well studied yet. In this study, linear and non-linear rheological tests, and fracture energy density tests were conducted on three HMABs, one base asphalt binder and one styrene-butadienestyrene (SBS) modified asphalt binder. The results show that HMABs have significantly higher rutting resistance, even after experiencing non-linear viscoelastic deformation. However, low cracking resistance was observed for HMAB due to its low ductility and low stress dissipation at its crack tip. Therefore, cracking resistance of HMACs should be a concern if they’re subjected to tensile loading in application.

Evaluation of the effect of the loading frequency on Wöhler’s curve parameters of a high modulus asphalt concrete (HMAC)

The fatigue's behaviour of bituminous materials is affected by the loading frequency. For hot mix asphalt (HMA) with unmodified bitumen, previous research showed a decrease in fatigue life, under strain-control mode, by increasing loading frequency. However, the effect of loading frequency on polymer-modified HMA has not been investigated extensively and researchers have found opposite results using the same testing method in strain-controlled mode. This paper looks at how the loading frequency impacts Wöhler's law parameters (slope and intercept) of a high modulus asphalt concrete (HMAC) made with a polymer-modified bitumen. Under strain-controlled mode, Tensile-Compression tests (TC) on cylindrical samples were carried out at isothermal conditions (θ = 10°C) and three distinct frequencies (5, 10 and 25 Hz). The analysis of covariance (ANCOVA) was considered to compare Wöhler's law parameters from different frequencies. The results showed no statistical difference in the slope and the intercept values from all studied frequencies.

Comparative Study on Test Performance of Two Kinds of High Modulus Asphalt Concrete for the Steel Bridge Deck

Along with the popularization and application of the steel bridge in China, due to the high modulus of asphalt concrete with good waterproof, anti-fatigue, anti-aging and good performance, asphalt concrete with high modulus was widely used in steel bridge deck pavement, the test and comparative study of high modulus asphalt concrete were carried out based on two types of common high modulus asphalt concrete which include the casting type asphalt concrete and epoxy resin modified asphalt concrete, aims to further explore the performance features of the steel bridge deck with high modulus asphalt concrete, and provide help on the application of this asphalt concrete on the steel bridge deck.

Mechanical Properties of High-Modulus Asphalt Concrete Containing Recycled Asphalt Pavement: A Parametric Study

The recycling of asphalt pavement is a widespread practice around the world owing to its significant social, economic, and environmental advantages. High-modulus asphalt concrete (HMAC) possesses excellent rutting resistance and has received increased attention around the world. While many studies have been conducted on the performance of hot mix asphalt (HMA) containing reclaimed asphalt pavement (RAP), gaps remain in knowledge about producing HMAC containing RAP. This paper aims to investigate the performance of HMAC containing high percentages of RAP by conducting parametric laboratory tests. Design factors, including aggregate gradation, asphalt binder content, recycling agent dosage, and asphalt binder type, are evaluated in the laboratory. Tests conducted include dynamic modulus test, Marshall immersion test, modified Lottman test, three-point bending test, and rutting test. A modified regeneration method with adjusted mixing sequence is adopted to produce a mixture. It was found that low-penetration virgin-grade asphalt binder could produce good-quality HMA, though low-temperature cracking resistance remains a problem. Adjusting aggregate gradation and increasing asphalt binder content could improve its overall performance but not low-temperature cracking resistance. Increasing the dosage of aromatic extract recycling agent could improve HMA’s low-temperature cracking resistance, and a maximum dosage of 6% was proposed. Increasing the penetration grade of virgin asphalt binder with the addition of high-modulus additive could significantly improve its low-temperature and overall performance.

Behaviour of High-Modulus Asphalt Concrete from the Perspective of Deformation Characteristics - Stiffness

High-modulus asphalt concrete is a specific type of asphalt mixture which is used for several decades in pavement engineering. It was originally invented as a solution which should help to minimize the effects of permanent deformation caused mainly by heavy traffic and mainly during the periods with elevated temperatures. These mixtures are used either in binder or base courses, whereas for base courses, it is important to combine reasonably the high stiffness with good fatigue life to avoid premature pavement failures not caused by rutting but by fatigue cracking. In this respect, various types of HMAC used and designed in the Czech Republic were tested first and foremost to determine stiffness. The stiffness modules were tested according to EN 12607-26, test method IT-CY, at selected temperatures representing cold, moderate and high service temperatures. The susceptibility to temperature change can be shown by thermal susceptibility for each mixture. In the parallel test, specimens were laboratory age to identify the changes in stiffness caused by thermo-oxidative ageing. This allows calculating a simple measure of the ageing index. Not presented in this paper but performed as a very last test was resistance to crack propagation.

Numerical Characterization of High Modulus Asphalt Concrete Containing RAP: A Comparison among Optimized Shallow Neural Models

Knowing the relationship between the stiffness modulus and the empirical mechanical characteristics of asphalt concrete, road engineers may predict the expected results of costly laboratory tests and save both time and financial resources in the mix design phase. In fact, such a model would make it possible to assess a priori whether the stiffness of a specific mixture, characterised in the laboratory only by the common Marshall test, is suitable for the level of service required by the road pavement under analysis. In this study, 54 Marshall test specimens of high modulus asphalt concrete were prepared and tested in the laboratory to determine an empirical relationship between the stiffness modulus and Marshall stability by means of shallow artificial neural networks. Part out of these mixtures was characterised by different types of bitumen (20/30 or 50/70 penetration grade) and percentages of used reclaimed asphalt (RAP at 20% or 30%); a polymer modified bitumen was used in the preparation of the remaining Marshall test specimens, which do not contain RAP. For the complex and laborious identification of the neural model hyperparameters, which define its architecture and algorithmic functioning, the Bayesian optimization approach has been adopted. Although the results of this methodology depend on the predefined hyperparameters variability ranges, it allows an unbiased definition of the optimal neural model characteristics to be performed by minimizing (or maximizing) a loss function. In this study, the mean square error on 5 validation folds was used as a loss function, in order to avoid a poor performance evaluation due to the small number of samples. In addition, 3 different neural training algorithms were applied to compare results and convergence times. The procedure presented in this study is a valuable guide for the development of predictive models of asphalt concretes’ behaviour, even for different types of bitumen and aggregates considered here.

Performance properties of high modulus asphalt concrete containing high reclaimed asphalt content and polymer modified binder

ABSTRACT High modulus asphalt concrete (HMAC) mixtures are produced using hard grade binders or modified bitumen and are known to have exceptional resistance towards rutting and fatigue. Due to the similarity between hard binder and aged reclaimed asphalt (RA) binder, HMAC mixtures have great potential to incorporate higher percentages of RA material. Here we present a study evaluating the performance of HMAC mixtures incorporating high content of RA material. Both hard grade binder and polymer modified bitumen (PMB) were used for all the mixtures with RA content varying from 0% to 70%. The laboratory performance of mixtures was examined using wheel tracking test, semi-circular bend test, thermal stress restrained specimen test, water sensitivity test and four-point bending test. The results demonstrated that it is possible to develop HMAC mixtures with satisfactory performance using RA content up to 70%, by using PMB binder. The mixtures produced using PMB binder outperformed conventional hard grade binder mixtures especially for use in regions with extremely cold winters.

Performance evaluation of HMAC mixes produced with gilsonite modified bitumen for heavily trafficked roads

Abstract The structural distresses in the flexible pavements due to exponential increase in traffic volume, heavily loaded vehicles and changes in climatic conditions are decreasing the performance of the pavement and leading to premature failure. These structural distresses lead to increase in maintenance cost, decreases residual life of the pavement and cause delay to the road users due to lane closures. The concept of Perpetual pavements can be adopted as a solution to addresses these issues because of its enhanced design life with minimum traffic-disrupting reconstruction or maintenance. High modulus layer used in the perpetual pavement can be produced with hard grade bitumen. In this study Gilsonite is used as stiffening additive for modifying VG 30 to produce hard grade bitumen. The physical test results of modified bitumen with different percentages, show that 15% (by weight of VG 30) of gilsonite is the optimum percentage to produce hard grade bitumen according to the specifications of EME2 method. The results of resilient modulus and rutting test on High Modulus Asphalt Concrete (HMAC) mixes show that the modulus value is increased by 2.4 times and rut depth is decreased by 4 mm with conventional mixes. A pavement section for a design traffic of 300 msa has been designed for both conventional and HMAC mixes as per IRC:37-2018 guidelines. Based on the analysis, the thickness of DBM layer with Gilsonite modified bitumen has been decreased by 65 mm in comparison with conventional bitumen, because of which investment of money and use of natural resources like mineral aggregates will be saved.

Evaluation of Bituminous Mix Characteristics Prepared with Laboratory Developed High Modulus Asphalt Binder

Asphalt layers in India are widely constructed with the use of viscosity grade binder. The mixes prepared with this binder exhibit early distress because of uncontrolled heavy axle loads and high ambient temperature. Pavement engineering specialists are in search for improved performing pavement materials, more specifically on the top layer. As a matter of fact, the viscosity and stiffness of the asphalt binder play a critical role in the overall performance of pavements at elevated temperatures. The stiffer or hard binder shall provide solution for improving the performance. This article aims in evaluating the performance characteristics of high modulus asphalt concrete (HMAC) mixture from the laboratory-developed high modulus asphalt binder (HMAB). The HMAC mixes prepared with HMAB require a penetration value of 10/20 or 15/25 at 25 °C. The development of HMAB is assessed from the following laboratory tests (1) physical, (2) chemical and (3) rheological, while that of HMAC includes (1) Marshall properties, (2) tensile strength, (3) immersion-type rutting characteristics, and (4) resilient modulus tests. The developed HMAB has shown an increased performance grade (PG) of base binder from 64 to 76 °C. HMAC mix has shown remarkable resistance toward the permanent deformation than the base mix. Moreover, the resilient modulus of the HMAC was found to be improved by twice that of the base mix. Further, a pavement section model was designed for traffic of 300 msa, and the model performance was evaluated using IITPave and finite element analysis. HMAC pavement section was found to be more economical than pavement prepared with the base mix. The outcome of this study is expected to help pavement engineers and other agencies in the revision of guidelines for possible inclusion of polyphosphoric acid as an approved modifier for the production of HMAB.

Assessment of Impact of Aramid Fibre Addition on the Mechanical Properties of Selected Asphalt Mixtures.

Various additives to asphalt binders and asphalt mixtures improving their properties are being used more and more frequently in order to improve the durability of road pavements. Such additives include various types of fibres, including aramid fibres. Tests concerning the impact of aramid fibre addition on the properties of selected asphalt mixtures have been described herein. Two types of asphalt mixtures were assessed: high modulus asphalt concrete (HMAC) and stone mastic asphalt (SMA). The examined asphalt mixtures were assessed with regard to: resistance to rutting, resistance to water and frost as well as fatigue resistance. The conducted tests showed relatively small impact of aramid fibre addition on the improvement of some assessed properties of the analysed asphalt mixtures. The obtained results were also compared to results of the tests conducted by the other research team concerning the impact of aramid fibre addition on the properties of the other types of asphalt mixtures.