Asphalt Materials Research Articles

Investigation of fatigue performance of asphalt mixtures and FAM mixes with high recycled asphalt material contents

Using a high content of recycled asphalt material, including reclaimed asphalt pavement (RAP) or recycled asphalt shingles (RAS), can be economically and environmentally beneficial. However, aged binder in RAP/RAS is a main concern for fatigue cracking resistance, therefore a reliable and efficient performance-related test for evaluating the effect of RAP/RAS on pavement performance is critical for the best use of these materials. In this study, four types of asphalt mixtures with various RAP/RAS contents higher than 20% were sampled from Southern California after different times at high temperature in the silo. To investigate the fatigue performance of these mixtures, four-point beam (4PB) fatigue testing was performed on full asphalt mixtures, and the linear amplitude sweep (LAS) testing was applied to their corresponding fine aggregate matrix (FAM) mixes. Testing results from FAM mixes have been analyzed within the viscoelastic continuum damage (VECD) framework. The relationships between fatigue life and strain level have been established for FAM mixes and full mixtures separately. The LAS testing results were compared among the FAM mixes with the same type of asphalt material but with different silo hours, which shows a good agreement with the observations from the 4PB testing results from full mixtures. Analyses of fatigue performance of both FAM mixes and full mixtures indicate that fatigue life decreases with the increase of RAP content, as expected, and that silo time shows an important effect. Finally, a strong linear correlation has been found between the strain value at failure of LAS tests of FAM mixes and the strain value at one million cycles to failure predicted from 4PB tests of full mixtures. This indicates that LAS fatigue testing on FAM mixes could predict the fatigue performance of asphalt materials containing high contents of RAP/RAS and potentially be developed as a surrogate performance-related test for asphalt mix design and/or QC/QA.

Systematic evaluation of effects of recycled materials and mix design parameters on the rutting and cracking performance of asphalt mixes

Problems associated with the rutting and cracking of asphalt mixes call for the use of balanced mix design and thus have received close attention from researchers and practitioners. The increased use of recycled materials, such as recycled asphalt pavement (RAP) and recycled asphalt shingles (RAS), further complicates the performance of asphalt mixes. Most studies of RAP and RAS have focused on the inclusion of these recycled materials in asphalt mixes designed for research purposes, which could differ from mixes designed by contractors for practical use. Therefore, a systematic review is needed of the effects of recycled materials and mix design parameters on the rutting and cracking performance of mixes designed by contractors. In addition, contractors need guidance in developing asphalt mixes that meet specifications that require rutting and cracking tests instead of simply relying on trial and error. To address these needs, in this study, rutting and cracking tests of forty contractors’ asphalt mix designs were conducted and the most effective design parameters on the performance of asphalt mixes were presented and discussed. These mixes included different percentages of RAP or RAP/RAS, performance grades of binders, design gyration numbers, aggregate gradations, and other volumetric properties. The provided results and discussions can be used as guidance for contractors to improve their mix designs to meet specifications.

Determining the Environmental Potentials of Urban Pavements by Applying the Cradle-to-Cradle LCA Approach for a Road Network of a Midscale German City

This study used a cradle-to-cradle Life Cycle Assessment (LCA) approach to evaluate the environmental potentials of urban pavements. For this purpose, the urban road network of the City of Münster (Germany) was selected as the case study, and comprehensive data for several phases were collected. The entire road network is composed of flexible pavements designed according to specific traffic loads and consists of main roads (MRs), main access roads (MARs), and residential roads (RSDTs). Asphalt materials, pavement structures, and maintenance strategies are predefined for each type of road and are referred to as “traditional” herein. Some pavement structures have two possible maintenance strategies, denoted by “A” and “B”, with distinguished periods of intervention. To evaluate the impact of using recycled materials, we considered alternative pavement structures composed of asphalt materials containing a greater amount of reclaimed asphalt pavement (RAP). The study was carried out considering analysis periods of 20, 50, 80, and 100 years and using two indicators: non-renewable cumulative energy demand (nr-CED) and global warming potential (GWP). The results show that the use of higher amounts of RAP can mitigate negative environmental impacts and that certain structures and maintenance strategies potentially enhance the environmental performance of road pavements. This article suggests initiatives that will facilitate the decision-making process of city administrators to achieve more sustainable road pavement constructions and provides an essential dataset inventory to support future environmental assessment studies, particularly for European cities.

Deformation recovery characteristics of asphalt pavement material on steel bridge decks under nondestructive conditions

The composition and properties of high-performance asphalt materials for steel bridge deck pavements are quite different. At present, research on the properties of steel bridge deck pavements mainly focuses on the strength law and damage behavior at the loading stage; however, little research exists on the deformation recovery characteristics of materials during unloading. In order to evaluate the deformation recovery ability of steel bridge deck pavement materials in the unloading stage, the repeated creep and step-load recovery test is herein put forward as an alternative to the deficient creep step-load test. The internal stress and residual strain of three typical steel deck pavement materials—a gussasphalt mixture, an epoxy asphalt mixture, and a stone mastic asphalt mixture—were tested. By comparing the results of CSR test and RCSR test, it is found that RCSR test is more suitable for steel bridge deck paving materials.The recovery modulus under three different creep stress levels was calculated to evaluate the ability of the three materials to drive deformation recovery. At the same time, based on the basic theory of viscoelasticity, the fitting parameters of creep compliance were determined, and the strain recovery rates of three kinds of materials under different interval times were calculated. The results reveal that the recovery modulus of the epoxy asphalt mixture is the largest, about 7 times and 4 times as much as stone mastic asphalt and gussasphalt, respectively, and the self-driving ability of epoxy asphalt mixture is better than that of gussasphalt and stone mastic asphalt. Moreover, within the same time interval, the strain recovery rate of the gussasphalt mixture is the fastest; in 3.6 s, the strain recovery rate can reach 82%.

Study on micromechanisms of macro evaluation indexes for asphalt based on grey relation analysis

ABSTRACT Macro evaluation indexes (penetration, ductility and softening point) are considered as an important basis for rational evaluation of asphalt service performance, but their micromechanisms have not been further studied. Thus, in order to establish the micromechanisms of macro evaluation indexes for asphalt, grey relational analysis and molecular dynamics simulation were applied to the study. Based on the measured data, the macro evaluation indexes and the variation of asphalt components were analysed. Combined with the characteristics (bond energy and non-bond energy) of asphalt 12-component molecules, the relationship among macro evaluation indexes, asphalt components and asphalt 12-component molecular were analysed by grey relation. Correlation coefficients of different scale characteristics were calculated, and their relationships were defined. The results show that the correlation degree of asphalt components and macro evaluation indexes is asphaltene > resin > saturate > aromatic. The relationship of intramolecular bond energy and macro evaluation indexes is closer than that of intermolecular non-bond energy. Additionally, macro evaluation indexes can be reasonably explained by component molecules to form micromechanisms. The study results have a certain theoretical and practical value for rational evaluation and understanding of service performance for asphalt materials and provide a theoretical basis for anti-ageing, modification and rejuvenation of asphalt.

Laboratory simulation and mechanical performance of asphalt materials under the action of saline

Conventional asphalt mixture performs well in most asphalt pavement applications. However, blistering, which is a common phenomenon in semi-arid areas, is one distress mechanism caused by various detrimental salts resulting in the loss of adhesion at the interface of aggregates and bitumen. When moisture reaches this delaminated interface, it can lead to blistering under the action of heat and thermal expansion. There is heightened interest in the semi-arid areas to modify bitumen and enhance the mechanical properties of asphalt mixtures to address durability and cost-effectiveness issues. One of the approaches being investigated includes using renewable additives to promote a more environmentally friendly production of asphalt mixtures. In this study, two bitumens of penetration grades 40/60 and 50/70 were modified with various percentages of Teak (TK) fibre contents to prolong the service life of asphalt pavements in the semi-arid areas. The properties, including rheological information of base and TK fibre-modified bitumens, were obtained through rutting, penetration, thermal conductivity, and multiple stress creep recovery (MSCR) tests. Base and TK fibre-modified bitumens were soaked in different sodium hydrogen carbonate (NaHCO3) solution concentrations for varying durations. The MSCR test was used to investigate the mechanical performance of the bitumen and binder mastics under salt action. TK fibre modified bitumens demonstrated better rutting resistance, reduced penetration and lower thermal conductivity. The test results indicated that all binder mastics with TK fibres had reduced shear strain, higher recovery, and higher non-recoverable creep compliance than the base bitumen. The TK fibre-modified binders showed better resistance to the action of salt than the base bitumen but exhibited an increase in shear strain, reduction in recovery and increase in non-recoverable creep compliance for soaked samples with increasing salt content. Both base bitumens exhibited excessive softening and showed negative recovery at stress levels from 0.5 kPa with increased soaking duration and salt content. These results show that the optimum level of TK fibres was 2% by weight of bitumen. The results from this study are encouraging for the potential use of TK fibres to improve the performance of asphalt mixtures in semi-arid field conditions where the presence of salt, and specifically NaHCO3, is expected.

Effect of aging and temperature on milling-induced stresses and cracks in Hot Mix Asphalt (HMA) pavements

The majority of the pavements in the world are surfaced with asphalt mixes. Milling is a necessary step for the removal of aged or distressed Hot Mix Asphalt (HMA) materials and recovery of Reclaimed Asphalt Pavement (RAP) for rehabilitation of asphalt pavements. The objective of this study was to predict the milling-induced stresses for two asphalt mixes. Using laboratory-measured stiffness, a three-dimensional finite element model (3-D FEM) was developed and validated with drop tower impact tests. The models were simulated at 25 °C and 60 °C, with unaged, 60 months, and 120-month aged conditions. Viscoelastic and Drucker-Prager models with the maximum principal stress failure criterion and the erosion method were utilized to predict failure. Results showed that the milling-induced stress zone increases significantly with increased stiffness/aging. Milling at 25 °C results in greater stress penetration depth than at 60 °C and leads to the formation of cracks below the milling line.

Investigation on aging resistance of ternary compound carbon nitride (CN-Bi-Tr-DC) modified asphalt

Asphalt aging is one of the key factors affecting the service life of asphalt pavement. Asphalt materials are prone to irreversible performance degradation under ultraviolet (UV) irradiation. In this study, a ternary composite carbon nitride modifier (CN-Bi-Tr-DC) with excellent compatibility with asphalt binder was prepared. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and ultraviolet visible near infrared spectroscopy (UV–Vis-NIR) were used to characterize the micro morphology and light absorption rate of the modifier. The results showed that the long organic chains were successfully grafted onto the surface of the ternary composite carbon nitride modifier. In addition, the ultraviolet absorption rate of CN-Bi-Tr-DC is 65%. Dynamic shear rheometer (DSR) was used to investigate the high and low temperature performance and fatigue resistance of CN-Bi-Tr-DC modified asphalt. CMAI, G-RAI, ICO and ISO were used to evaluate the long-term aging performance of CN-Bi-Tr-DC modified asphalt. The test results demonstrated that the addition of CN-Bi-Tr-DC could improve the anti-ultraviolet aging performance of asphalt binder, and the improvement effect was most obvious when the content of CN-Bi-Tr-DC was 2–4%.

“Simplified” Cracking Tests: Evaluation of the IDEAL-CT Performed Using a Marshall Testing Platform

Abstract In considering the implementation of a cracking test for asphalt mixes, attention should be given to both the accuracy and the practical implications of equipment cost and ease of use. This study evaluated the applicability of the indirect tensile asphalt cracking test (IDEAL-CT) performed using a Marshall frame with an in-house-assembled data acquisition instrumentation, compared with the Illinois flexibility index test (I-FIT) protocol using a modern asphalt materials performance test (AMPT). Both flexibility index (FI) and cracking resistance index (CRI) values were obtained from the I-FIT tests. Mixes representing five in-service pavements exhibiting different levels of cracking performance are included. Despite an unstable (and out of specification) loading rate on the Marshall testing frame, IDEAL-CT test results compared favorably with those of the I-FIT performed on the AMPT. The CTIndex exhibited less variability than the FI but more variability than the CRI. The CTIndex appears to discriminate cracking-related behavior in a manner consistent with the FI and CRI. This study indicates the potential for using the IDEAL-CT on a Marshall frame—offering laboratories potentially significant savings in both equipment and specimen preparation costs.

Performance Evaluation of Asphalt Binder Modified by Natural Rock Asphalt

Rock asphalt is one of the widely distributed resources in nature. Therefore, this study employs natural rock asphalt as an additive. The focus of this study is to look at the potential of using natural rock asphalt as an asphalt binder modifier. The study looks at five different percentages of modified asphalt (NRA) concentration from Anbar factory asphalt for oxidized bitumen: 0%, 5%, 10%, 20%, and 30%. The results show that using modified natural rock asphalt increased the mechanical qualities of basic asphalt, such as penetration and softening point, flash point, and viscosity. In addition, the current results show that the asphaltic materials that can be used in paving according to the measuring of conventional tests such as ductility, penetration, and others. Furthermore, the findings indicate that modified asphalt has lower temperature sensitivity.

Research on gradient characteristics and its prediction method of induction heating asphalt concrete

In this paper, a method to predict the healing effect of induction heating asphalt concrete at vertical depths was proposed and verified. At first, AH-70 asphalt concrete and SBS modified asphalt concrete of AC-13 gradation were designed and prepared. R-DT (Relationship of Depth and Temperature) was quantified through induction heating test. R-HT (Relationship of Healing rate and Temperature) was quantified through fracture-healing–fracture test and X-ray micro computed tomography test with oven heating. Then, linear regression was used to verify the rationality of R-HT compared with the pre-relationship in previous studies. Finally, R-DH (Relationship of Depth and Healing rate) was predicted by fitting approach. It was found that R-DT and R-HT presented significant linearity, the existence of which was independent from the type of asphalt materials. While, more sensitive of SBS modified asphalt concrete showed that the response to gradient characteristics of R-DT was related to the higher overall temperature. Additionally, R Square-values = 0.963 of linear regression proved the oven heating method was suitable for the quantification and prediction of gradient characteristics. Furthermore, the prediction of R-DH was obtained successfully, which established the continuous distribution of the healing effect at vertical depths and revealed the linear relationship of the continuous distribution.

BIM-Based Pavement Management Tool for Scheduling Urban Road Maintenance

The latest advancements in road asphalt materials and construction technologies have increased the difficulty for engineers to select the appropriate pavement design solution with consideration of proper timing for maintenance planning. On the other hand, Building Information Modeling (BIM) tools allow practitioners to efficiently store and manage large amounts of data, supporting decision making in road asphalt pavement design and management. The present work focused on the elaboration of a BIM-based maintenance analysis tool for the specific evaluation of several condition indicators and the selection of proper maintenance solutions designed to include alternative materials and advanced recycling technologies. A traditional BIM workflow was integrated with additional user-defined property sets to investigate the need for maintenance at the present date and predict the degradation curve of the condition indicators through the least square interpolation of time series of data. The analysis tool also provided the selection of available pavement alternatives from a library of designed solutions based on their compliance with project-specific constraints (maximum budget, minimum useful life, and availability of secondary raw materials and in-place recycling technologies). The proposed BIM tool aims to be a practical and dynamic way to integrate maintenance planning considerations into road pavement design, encouraging the use of digital tools in the road industry and ultimately supporting a pavement maintenance decision-making process oriented towards a circular economy.

At the frontline for mitigating the undesired effects of recycled asphalt: An alternative bio oil-based modification approach

Soybean oil-derived modifiers were used for the improvement of properties of asphalt materials prepared for a pavement demonstration project. The rheological properties of base, biomodified and extracted binders were measured/compared using rheometers. The binder modification resulted in a decrease of 1.2 °C and 2.3 °C in, respectively, the high-and low-temperature grades of base binder, and when the effect of RAP binder was considered, the continuous performance grade (PG) became almost identical with that of base/control binder. Due to the biomodification and the presence of RAP, the binder’s elastic recovery (R) increased by 8.0% and its non-recoverable creep compliance (Jnr) decreased by 0.13 kPa−1. The tests conducted to evaluate the mechanical performance of the mixtures proved the efficacy of the bio-modifiers used in reversing the undesired effects of reclaimed asphalt pavement (RAP) and improving the performance of asphalt pavements at different temperatures. For instance, the Hamburg wheel tracking (HWT) test results revealed that the presence of bio-modifiers resulted in the increase of stripping inflection point (SIP) by 3619 passes. The disk-shaped compact tension (DCT) test proved the effectiveness of the bio-modifiers used, as these modifiers increased the fracture energy by 113 J/m2. The master curves constructed for the asphalt binders and mixtures indicated an increased stiffness/elasticity at intermediate and high temperatures.

Feasibility study on using asphalt pavements as heat absorbers and sensible heat storage materials in solar air heaters: An experimental study

Asphalt pavements are affordable infrastructures exposed to solar irradiation for a long time a day, and they experience considerable high temperatures. Due to high thermal capacity, asphalt pavements can store high sensible thermal energy during daytime hours and release it when solar irradiation is negligible or absent. The current study investigates the heat dynamics and thermal efficiency of asphalt solar air heaters (SAHs) utilizing asphalt materials that function as both heat absorbers and sensible heat storage units. To this aim, a 1.2 m2 single-glazed baffled SAH prototype was constructed, and its heat dynamics were monitored on cold and mild winter days at two different air mass flow rates of 0.02 kg/s and 0.03 kg/s. The constructed SAH uses black stainless-steel baffles to produce a serpentine air passageway and improve turbulence and heat exchange rates. The acquired data illustrates that the maximum intake and exhaust air temperature difference reaches up to 14 °C and 24 °C on cold and mild winter days, respectively. When the solar irradiation was negligible in the evening, the asphalt pavement serves as sensible heat storage and heats the passing airflow up to 8 °C and 12 °C at sunset on cold and mild winter days, respectively. This issue causes the collector thermal efficiency to reach as high as 80%. Therefore, using asphalt materials is a feasible approach to simultaneously serve as heat absorber and sensible heat storage.

Water vapor diffusion models in asphalt mortar considering adsorption and capillary condensation

Water vapor diffusion persistently and extensively existing in asphalt pavement is one of the important contributors to moisture-induced damage. Non-Fickian diffusion of water vapor in asphalt mortar has not been deeply understood due to the lack of quantitative characterization of water molecular transport in micropores affected by the adsorption and capillary condensation. The objective of this study is to establish diffusion models considering the effects of the adsorption and capillary condensation and quantitatively characterize the dependence of diffusion coefficient on the humidity and sample thickness. The diffusion characteristics of water vapor in asphalt mortar with various thicknesses under various humid conditions were investigated using a standard wet cup method. The results suggest that in the steady diffusion the measured mass loss of diffusive water vapor linearly increases with time. The apparent diffusion coefficients determined by the first Fick’s law demonstrate a nonlinear rapid reduction from 51.45×10–9 m2/s to 12.66×10–9 m2/s while the relative humidity varies from 22% to 95%. The diffusion coefficient nonlinearly decreases from 40.92×10–9 m2/s to 24.71×10–9 m2/s while the sample thickness increases from 3.62 mm to 16.34 mm. The molecular transports in gaseous flow, surface flow, and capillary condensate flow were introduced to formulate the effects of adsorption and capillary condensation. Combining the measured adsorption isotherm of water vapor in asphalt mortar, a diffusion model considering adsorption was derived and quantitatively characterizes the diffusion coefficients varying with the relative humidity. The dependence on relative humidity is attributed to the thickening of adsorbed water film in high humidity that changes the diffusivities in gaseous flow and surface flow. Another diffusion model considering capillary condensation was established to formulate the thickness-dependent diffusion coefficients in asphalt mortar. The dependence on the sample thickness is explained as the variable ratio of the diffusion in capillary condensate flow to the overall diffusion in a thick sample. This study provides a feasible approach to quantifying the environment-dependent diffusion characteristics and promotes the understanding of non-Fickian diffusion of water vapor in asphaltic materials.

Cold in-place recycling of aged and deteriorated asphalt and concrete pavements

This study focuses on implementing two distinct recycling methods, the reclaimed asphalt pavement and the reclaimed concrete material, on classical road pavements, by totally replacing the surface or base courses with ones made with recovered materials. The majority of the road networks in the eastern European countries were built between 1950 and 1980 and are, nowadays, aged and degraded. Within this frame, the cold in-place recycling methods were developed, which can be applied to both asphalt and concrete pavements. During the cold in-place recycling process, the reclaimed asphalt or concrete materials do not leave the construction site at all, but they are processed on the spot and reused immediately. Thus, the material is granulated to the desired depth, mixed with the binding agent and water and then repaved and compacted in a new layer. One of the most significant benefits of the cold in-place recycling process is that the material is simultaneously recycled and mixed with the binding agent, enabling the road pavement to be strengthened without the need to import expensive virgin aggregates. This work describes the manufacturing technology and the equipment train used to cold recycle aged and deteriorated asphalt and concrete pavements.

Elaboration of concrete blocks with addition of crushed asphalt pavement

The main objective of this research is to determine the mechanical behavior of crushed asphalt, considered as the excess material in the paving of roads in Colombia. Initially, this raw material must be ground and, later, articulated to elaborate blocks that can be used as dividing elements in the construction of any civil works project. For the execution of this experimental research, concrete cubes were developed with different percentages of crushed asphalt that were 25%, 50%, and 75% of recycled asphalt addition, considering the Colombian technical standards procedures to develop the mechanical and physical tests. The results indicated that samples with 25% recycled crushed asphalt were determined as the best replacement of the sample for the realization of the blocks which dimensions of 9 cm × 17 cm × 34 cm, with vertical perforations of 4 cm × 3 cm × 10 cm. Finally, tests related to water absorption, the mechanical resistance to compression gave very good results, concluding that concrete blocks with the addition of recycled ground asphalt material can be used in the construction industry with an emphasis on sustainable construction, thus allowing the development of new materials that provide an environmental care contributing thus to the efficient use of natural resources.

Modifying The Rheological Properties Of Asphalt Using Waste Additives and Air Blowing and Studying The Effect Of Time Aging On The Modified Samples

The modification of asphaltic materials with polymeric materials and other additives is one of the most important processes or modifications that take place on asphalt materials. The purpose of these modified that take place is the main purpose of which is to obtain asphaltic materials with a good specifications for the purposes for which it is used, whether that use is in the field of paving, flattening or as a mastic. This study included the treatment of asphaltic materials with modified materials represented by polyvinyl chloride and spent lubricating oils. The asphalt was treated with these additives in different percentages and in the presence of sulfur again and again in the presence of sulfur with anhydrous ferric chloride as acatalyst at a temperature of 150 ° C. An air blowing process was used on both paths. The rheological properties of the original asphalt and the modified and original samples were measured (penetration, softining point and ductility In addition, penetration index was calculated) for all samples After that, the samples were left for the aging factors for a period of 12 months. The rheological properties were measured again. This study gave a good samples when compared to standard samples.

Analysis of micromechanical properties of algae bio-based bio-asphalt-mineral interface based on molecular simulation technology

Bio-asphalt is a renewable material with good application prospects. In this study, different ratios of bio-oil were mixed into the base asphalt to simulate bio-asphalt. Through molecular dynamics software, the micro-mechanical properties of the bio-asphalt with different ratios of bio-oil were simulated and studied. By calculating the interfacial energy between asphalt and mineral materials with different amounts of bio-oil, the author found that the higher the amount of bio-oil, the lower the interfacial energy between it and the mineral, which is inversely proportional. Subsequently, the author used molecular dynamics software to analyze the diffusion law of asphalt with different amounts of bio-oil on the surface of mineral aggregates. The simulation results show that the addition of organisms reduces the diffusion rate of asphalt on the surface of the mineral material, thereby affecting the formation of the interface between the asphalt and the mineral material. Therefore, if bio-asphalt is to be widely used in road engineering, it must be modified. The reason for the poor performance of bio-asphalt must be found before modification. The research in this article will provide technical guidance and direction for future modification of bio-asphalt.

Evaluation of self-healing characteristics of asphalt materials by intermittent loading tests

A self-healing index, recovery modulus ratio (RG ), was proposed to evaluate the self-healing characteristics of asphalt materials with intermittent loading tests which is more consistent with the traffic loading. In this study, three types of asphalt binders and six types of asphalt mastics were performed on intermittent loading tests. Based on the test results, RG was demonstrated to be a suitable self-healing index for evaluating the effect of filler-asphalt ratio and stress level on the self-healing performance of asphalt materials, and there was a linear positive relationship between it and the growth rate of fatigue life. A higher asphalt-filler ratio deteriorates the self-healing performance of #70 asphalt mastic. However, there is an adverse impact on the harder #50 asphalt mastic. The higher stress level worsens the self-healing performance of base asphalt; however, it has an advantageous influence on SBS modified asphalt within a certain stress level range.