Lignin, one of the most abundant natural polymers, has been extensively studied as an additive in... more Lignin, one of the most abundant natural polymers, has been extensively studied as an additive in bituminous binders. Even though the lignin improves the overall resistance against oxidative aging of bitumen, it could lead to high thermal cracking sensitivity. In this study, a bio-oil (i.e., rapeseed oil) is implemented in lignin modified bitumen to ameliorate characteristics, such as the resistance to fatigue and cracking. The long-term aging of bitumens formulated by different proportions of bio-oil was simulated by the pressure aging vessel method. Fourier Transform Infrared Spectroscopic (FTIR) results demonstrated lignin has a remarkable anti-aging effect, but adding bio-oil will slightly deteriorate the anti-aging effect. The Brookfield rotational viscometer showed that the addition of bio-oil was able to reduce the binder's viscosity observably, thereby improving the workability of bitumen. The frequency sweep tests revealed that lignin increased the stiffness and improved the thermal stability. Also, the multiple stress creep recovery tests corroborated that lignin significantly enhanced the rutting resistance of binders. The fatigue and thermal cracking properties of lignin modified binder could be strengthened by increasing bio-oil content which is confirmed from both linear amplitude sweep, Glover-Rowe parameter, and Bending Beam Rheometer tests. Moreover, the relaxation test results demonstrated that bio-oil decreased the residual stress ratio and relaxation time dramatically. Overall, this study has shown preliminary conclusions on the incorporating of bio-oil to enhance the medium-low temperature properties of lignin modified binders. In the meantime, bio-oil did not interfere with the improvement influence of lignin on the neat bitumen regarding high-temperature performance.
Advanced Testing and Characterization of Bituminous Materials, 2009
Behavior of asphalt mixes and typical failures of the pavement structure, which are influenced by... more Behavior of asphalt mixes and typical failures of the pavement structure, which are influenced by high or low temperatures, are most significantly influenced by the behavior of bituminous binder. The experimental method for assessment of asphalt mix characteristics at low temperatures has not been set in European standards yet, however a test method based on the experience of Prof. Arand is at the moment in preparation. Using this test method the specimen is exposed in a special chamber to decreasing temperature of the ambient environment without the possibility of shrinkage. In the Czech Republic the asphalt mix behavior in the range of low temperatures is so far observed and assessed using the approach of bending beam test at the zero temperature or even lower temperatures. A second test method, which is usually done in parallel on the same testing apparatus, is the relaxation test. The practical part of the paper addresses the testing, analysis and evaluation of low temperature characteristics for various HSM (high stiffness modulus) asphalt mixes as well as of asphalt mixes for SAL (stress absorbing layers).
Transportation Research Record: Journal of the Transportation Research Board, 2016
Asphalt concrete has the advantageous ability to heal. During rest periods, damage present in the... more Asphalt concrete has the advantageous ability to heal. During rest periods, damage present in the material is restored to a certain extent. Healing of the material can be observed in its regaining of strength and stiffness after rest periods. In this paper, a new test method is presented. It was developed to increase the understanding of the healing phenomenon. The test method focused on asphalt as it was assumed to be the driver of the healing performance. The test method assessed the healing performance of asphalt in stiffness and strength by testing the bond strength in tensile mode of two pieces of asphalt that were assembled under controlled temperature and stress conditions. With the test method, healing tests were performed on one type of binder; the load level during healing and the healing time were varied. The test results showed that after a short healing time of only 6 min, a significant amount of healing could be detected. That finding indicates the importance of adhesi...
Transportation Research Record: Journal of the Transportation Research Board, 2016
Asphalt concrete has the advantageous ability to heal. During rest periods, damage present in the... more Asphalt concrete has the advantageous ability to heal. During rest periods, damage present in the material is restored to a certain extent. Healing of the material can be observed in its regaining of strength and stiffness after rest periods. In this paper, a new test method is presented. It was developed to increase the understanding of the healing phenomenon. The test method focused on asphalt as it was assumed to be the driver of the healing performance. The test method assessed the healing performance of asphalt in stiffness and strength by testing the bond strength in tensile mode of two pieces of asphalt that were assembled under controlled temperature and stress conditions. With the test method, healing tests were performed on one type of binder; the load level during healing and the healing time were varied. The test results showed that after a short healing time of only 6 min, a significant amount of healing could be detected. That finding indicates the importance of adhesi...
Economic advantages and environmental benefits encourage the use of recycled materials for road c... more Economic advantages and environmental benefits encourage the use of recycled materials for road construction. Usually, however, these materials have lower stiffness and strength characteristics than typically used natural materials. Because of these inferior material properties, use of recycled aggregate materials for unbound road base construction may result in increased rutting, differential settlement, and reflective crack propagation. Placement of reinforcement between the underlying soil layer and the aggregate layer has been proposed to improve the load-carrying capacity of road bases constructed from recycled aggregate materials. To investigate the viability of such an approach, finite element analyses were performed of asphalt concrete pavements with base layers consisting of reinforced unbound recycled aggregate materials. The response of such pavements was compared with that of pavements consisting of unreinforced natural aggregates. The criteria chosen for comparison were...
ABSTRACT: Seismic micro hazard zonation is the first step towards a seismic risk analysis and mit... more ABSTRACT: Seismic micro hazard zonation is the first step towards a seismic risk analysis and mitigation strategy. Essential here is to obtain a proper understanding of the local subsurface conditions. In this study it is demonstrated that it is possible to make better use ...
Abstract Gradation measurement is important for quality control of pavement construction. Compute... more Abstract Gradation measurement is important for quality control of pavement construction. Computed tomography (CT) can capture the microstructure images of asphalt mixture. However, an accuracy digital image processing method should be developed. In this study, fuzzy network, multilevel threshold and morphological methods are utilized to reduce the noise, enhance the contrast and segment images. The 2D aggregate gradation obtained from the digital image segmentation procedure is transferred into 3D gradation by stereological method. The results show that fuzzy network can balance the noise reduction and contrast enhancement. The multilevel Otsu’s threshold method can obtain the two thresholds automatically. The morphological processing and watershed transformation can fill the holes in the image and break the aggregate connections. By comparing the calculated gradation and the designed gradation, the image processing procedure proposed in this paper can be utilized to obtain the gradation information of AC, SMA and OGFC accurately and effectively.
International Journal of Pavement Engineering, 2014
ABSTRACT Tire operating temperature is an important concern not for both tire manufacturers and h... more ABSTRACT Tire operating temperature is an important concern not for both tire manufacturers and highway agencies which is known to have a major influence on the tire traction. Most of the past tire-pavement interaction studies were focused on the performance of the tire while giving limited importance to the effect of the pavement texture profile. This paper presents a methodology of coupled thermo-mechanical finite element (FE) model to determine the progressive temperature development in tire cross section. The model is developed for a test tire rolling over a FE mesh of an asphalt pavement surface, and the effect of the developed temperature on the hysteretic friction is evaluated. Such a model will enable tire manufacturers to come up with optimized tire design, on the other hand, road agencies can design their friction test protocol. In this study, an attempt has been made to examine the developed tire-temperature in time at different regions of tire
Transportation Research Record: Journal of the Transportation Research Board, 2015
Tire–road interaction addresses safety with respect to braking friction and energy efficiency in ... more Tire–road interaction addresses safety with respect to braking friction and energy efficiency in the context of rolling resistance. These phenomena are coherent, but their engineering solutions can be contradictory. For example, highly skid-resistant surfaces may not be ideal for fuel economy, but surfaces with low rolling resistance may be prone to skidding. Several experimental and numerical studies have investigated the individual phenomena, but insufficient attention has been paid to studying them coherently. The present study computed braking friction and rolling resistance for various operating parameters and their coherent response for each parameter with the use of a thermomechanical contact algorithm. Micromechanical finite element simulations of a rolling or braking pneumatic tire against selected asphalt concrete surfaces were performed for various operating conditions, such as tire load, inflation pressure, speed, and ambient air and pavement temperatures. The coefficien...
Asphalt Paving Technology: Association of Asphalt Paving Technologists-Proceedings of the Technical Sessions
A rapid test performed on easy to prepare specimens, that gave decisive answers for materials cha... more A rapid test performed on easy to prepare specimens, that gave decisive answers for materials characteristics required for pavement designs was presented. The principle of semi-circular bending test was shown to determine the characteristics of the material investigated. A disc cut form gyratory sample, or core and sawn into two equal parts resulting in two semi-circular specimens. It was found that test described fulfilled the requirements of the materials tested.
ABSTRACT: At the previous conference the beginning of an extensive experimental and analytical in... more ABSTRACT: At the previous conference the beginning of an extensive experimental and analytical investigation into the mechanisms leading to the initiation and propagation of damage in asphalt concrete pavements was reported. The objectives of this Asphalt Concrete Response (ACRe) project were twofold, firstly a 3-dimensional, strain rate sensitive, temperature and loading history dependent constitutive model would be formulated and implemented in the finite element package CAPA-3D. Secondly, the necessary experimental set-ups, testing procedures and data-analysis methods for determination of the model parameters would be developed. At the time the prototype formulation of the model was reported, along with preliminary test results and the way in which the model parameters were determined on the basis of the experimental results. A simulation of the dynamic non-linear response of a pavement was included to demonstrate the possibilities of the approach. In the past years, the project ...
Transportation Research Record: Journal of the Transportation Research Board, 2014
This paper describes a project that is part of NL-LAB, a larger, long-term program at Delft Unive... more This paper describes a project that is part of NL-LAB, a larger, long-term program at Delft University of Technology, Netherlands, which aims to establish the predictive capacity of the current European functional tests for Dutch asphalt concrete (AC) mixtures. In this NL-LAB program, the functional characteristics of resistance to rutting (EN 12697–25), fatigue (EN 12679-24), stiffness (EN 12697–26), and moisture sensitivity (EN 12697-12 and EN 12697–23) are determined for specimens that are (a) mixed and compacted in the lab, (b) mixed in the plant and compacted in the lab, and (c) mixed in the plant and compacted in the road. Eventually, these tests will provide insight into the effect of mixing and compaction on the functional characteristics. The project described in this paper focused on the indirect tensile strength (ITS) and the triaxial cyclic compression test for two AC mixes. The properties found for all three stages of preparation were analyzed with the use of formalisti...
Bituminous binders are known to have microstructures at typical length scales of micrometers. Thi... more Bituminous binders are known to have microstructures at typical length scales of micrometers. This microstructure can be probed with Atomic Force Microscopy (AFM). Now that worldwide several research groups are reporting AFM results on bitumen, it is becoming important to improve the understanding of the reproducibility and objectivity of the technique for studying bituminous samples. When reproducibility and stability are proven, AFM can be a tool for asphalt professionals to rapidly screen bituminous binders. In this context two independent laboratories have developed a standard method for preparing and conditioning bitumen for AFM imaging. By means of an inter-laboratory comparison of independently imaged specimen, the reproducibility of microstructure measurements was investigated. A quantitative comparison on different microstructures was developed, and the consistency of independently obtained results was confirmed. The results from both labs were comparable: the microstructural properties were found to be randomly distributed within a 5% interval. Also the influence of temperature on the microstructure was demonstrated to be reproducible and consistent. With the increase of temperature, the microstructure gradually disappeared, however traces of the microstructure remained visible up to the highest measurement temperature of 60°C. It is concluded that given well defined sample preparation and measurement procedures, the microstructure of bitumen can be reproducibly imaged by AFM from room temperature up to temperatures where bitumen has become soft and too sticky to be probed by the same setup as used for lower temperatures.
EQUATION SECTION 1 The necessity of realistic non-linear, three-dimensional material modeling for... more EQUATION SECTION 1 The necessity of realistic non-linear, three-dimensional material modeling for asphalt concrete is demonstrated by using such a model to simulate two laboratory tests. For this demonstration the Indirect Tensile Test (ITT) and Semi Circular Bending (SCB) test are used, two relatively simple tests that result in a complicated stress state in the specimen. It becomes quite clear that the observed response can not be modeled without realistic damage descriptions. Prior to these examples of model application the material model used for the simulations is presented and its suitability to describe the response of asphalt concrete is verified. This verification is based on the simulation of laboratory tests used to provide the model parameters.
Lignin, one of the most abundant natural polymers, has been extensively studied as an additive in... more Lignin, one of the most abundant natural polymers, has been extensively studied as an additive in bituminous binders. Even though the lignin improves the overall resistance against oxidative aging of bitumen, it could lead to high thermal cracking sensitivity. In this study, a bio-oil (i.e., rapeseed oil) is implemented in lignin modified bitumen to ameliorate characteristics, such as the resistance to fatigue and cracking. The long-term aging of bitumens formulated by different proportions of bio-oil was simulated by the pressure aging vessel method. Fourier Transform Infrared Spectroscopic (FTIR) results demonstrated lignin has a remarkable anti-aging effect, but adding bio-oil will slightly deteriorate the anti-aging effect. The Brookfield rotational viscometer showed that the addition of bio-oil was able to reduce the binder's viscosity observably, thereby improving the workability of bitumen. The frequency sweep tests revealed that lignin increased the stiffness and improved the thermal stability. Also, the multiple stress creep recovery tests corroborated that lignin significantly enhanced the rutting resistance of binders. The fatigue and thermal cracking properties of lignin modified binder could be strengthened by increasing bio-oil content which is confirmed from both linear amplitude sweep, Glover-Rowe parameter, and Bending Beam Rheometer tests. Moreover, the relaxation test results demonstrated that bio-oil decreased the residual stress ratio and relaxation time dramatically. Overall, this study has shown preliminary conclusions on the incorporating of bio-oil to enhance the medium-low temperature properties of lignin modified binders. In the meantime, bio-oil did not interfere with the improvement influence of lignin on the neat bitumen regarding high-temperature performance.
Advanced Testing and Characterization of Bituminous Materials, 2009
Behavior of asphalt mixes and typical failures of the pavement structure, which are influenced by... more Behavior of asphalt mixes and typical failures of the pavement structure, which are influenced by high or low temperatures, are most significantly influenced by the behavior of bituminous binder. The experimental method for assessment of asphalt mix characteristics at low temperatures has not been set in European standards yet, however a test method based on the experience of Prof. Arand is at the moment in preparation. Using this test method the specimen is exposed in a special chamber to decreasing temperature of the ambient environment without the possibility of shrinkage. In the Czech Republic the asphalt mix behavior in the range of low temperatures is so far observed and assessed using the approach of bending beam test at the zero temperature or even lower temperatures. A second test method, which is usually done in parallel on the same testing apparatus, is the relaxation test. The practical part of the paper addresses the testing, analysis and evaluation of low temperature characteristics for various HSM (high stiffness modulus) asphalt mixes as well as of asphalt mixes for SAL (stress absorbing layers).
Transportation Research Record: Journal of the Transportation Research Board, 2016
Asphalt concrete has the advantageous ability to heal. During rest periods, damage present in the... more Asphalt concrete has the advantageous ability to heal. During rest periods, damage present in the material is restored to a certain extent. Healing of the material can be observed in its regaining of strength and stiffness after rest periods. In this paper, a new test method is presented. It was developed to increase the understanding of the healing phenomenon. The test method focused on asphalt as it was assumed to be the driver of the healing performance. The test method assessed the healing performance of asphalt in stiffness and strength by testing the bond strength in tensile mode of two pieces of asphalt that were assembled under controlled temperature and stress conditions. With the test method, healing tests were performed on one type of binder; the load level during healing and the healing time were varied. The test results showed that after a short healing time of only 6 min, a significant amount of healing could be detected. That finding indicates the importance of adhesi...
Transportation Research Record: Journal of the Transportation Research Board, 2016
Asphalt concrete has the advantageous ability to heal. During rest periods, damage present in the... more Asphalt concrete has the advantageous ability to heal. During rest periods, damage present in the material is restored to a certain extent. Healing of the material can be observed in its regaining of strength and stiffness after rest periods. In this paper, a new test method is presented. It was developed to increase the understanding of the healing phenomenon. The test method focused on asphalt as it was assumed to be the driver of the healing performance. The test method assessed the healing performance of asphalt in stiffness and strength by testing the bond strength in tensile mode of two pieces of asphalt that were assembled under controlled temperature and stress conditions. With the test method, healing tests were performed on one type of binder; the load level during healing and the healing time were varied. The test results showed that after a short healing time of only 6 min, a significant amount of healing could be detected. That finding indicates the importance of adhesi...
Economic advantages and environmental benefits encourage the use of recycled materials for road c... more Economic advantages and environmental benefits encourage the use of recycled materials for road construction. Usually, however, these materials have lower stiffness and strength characteristics than typically used natural materials. Because of these inferior material properties, use of recycled aggregate materials for unbound road base construction may result in increased rutting, differential settlement, and reflective crack propagation. Placement of reinforcement between the underlying soil layer and the aggregate layer has been proposed to improve the load-carrying capacity of road bases constructed from recycled aggregate materials. To investigate the viability of such an approach, finite element analyses were performed of asphalt concrete pavements with base layers consisting of reinforced unbound recycled aggregate materials. The response of such pavements was compared with that of pavements consisting of unreinforced natural aggregates. The criteria chosen for comparison were...
ABSTRACT: Seismic micro hazard zonation is the first step towards a seismic risk analysis and mit... more ABSTRACT: Seismic micro hazard zonation is the first step towards a seismic risk analysis and mitigation strategy. Essential here is to obtain a proper understanding of the local subsurface conditions. In this study it is demonstrated that it is possible to make better use ...
Abstract Gradation measurement is important for quality control of pavement construction. Compute... more Abstract Gradation measurement is important for quality control of pavement construction. Computed tomography (CT) can capture the microstructure images of asphalt mixture. However, an accuracy digital image processing method should be developed. In this study, fuzzy network, multilevel threshold and morphological methods are utilized to reduce the noise, enhance the contrast and segment images. The 2D aggregate gradation obtained from the digital image segmentation procedure is transferred into 3D gradation by stereological method. The results show that fuzzy network can balance the noise reduction and contrast enhancement. The multilevel Otsu’s threshold method can obtain the two thresholds automatically. The morphological processing and watershed transformation can fill the holes in the image and break the aggregate connections. By comparing the calculated gradation and the designed gradation, the image processing procedure proposed in this paper can be utilized to obtain the gradation information of AC, SMA and OGFC accurately and effectively.
International Journal of Pavement Engineering, 2014
ABSTRACT Tire operating temperature is an important concern not for both tire manufacturers and h... more ABSTRACT Tire operating temperature is an important concern not for both tire manufacturers and highway agencies which is known to have a major influence on the tire traction. Most of the past tire-pavement interaction studies were focused on the performance of the tire while giving limited importance to the effect of the pavement texture profile. This paper presents a methodology of coupled thermo-mechanical finite element (FE) model to determine the progressive temperature development in tire cross section. The model is developed for a test tire rolling over a FE mesh of an asphalt pavement surface, and the effect of the developed temperature on the hysteretic friction is evaluated. Such a model will enable tire manufacturers to come up with optimized tire design, on the other hand, road agencies can design their friction test protocol. In this study, an attempt has been made to examine the developed tire-temperature in time at different regions of tire
Transportation Research Record: Journal of the Transportation Research Board, 2015
Tire–road interaction addresses safety with respect to braking friction and energy efficiency in ... more Tire–road interaction addresses safety with respect to braking friction and energy efficiency in the context of rolling resistance. These phenomena are coherent, but their engineering solutions can be contradictory. For example, highly skid-resistant surfaces may not be ideal for fuel economy, but surfaces with low rolling resistance may be prone to skidding. Several experimental and numerical studies have investigated the individual phenomena, but insufficient attention has been paid to studying them coherently. The present study computed braking friction and rolling resistance for various operating parameters and their coherent response for each parameter with the use of a thermomechanical contact algorithm. Micromechanical finite element simulations of a rolling or braking pneumatic tire against selected asphalt concrete surfaces were performed for various operating conditions, such as tire load, inflation pressure, speed, and ambient air and pavement temperatures. The coefficien...
Asphalt Paving Technology: Association of Asphalt Paving Technologists-Proceedings of the Technical Sessions
A rapid test performed on easy to prepare specimens, that gave decisive answers for materials cha... more A rapid test performed on easy to prepare specimens, that gave decisive answers for materials characteristics required for pavement designs was presented. The principle of semi-circular bending test was shown to determine the characteristics of the material investigated. A disc cut form gyratory sample, or core and sawn into two equal parts resulting in two semi-circular specimens. It was found that test described fulfilled the requirements of the materials tested.
ABSTRACT: At the previous conference the beginning of an extensive experimental and analytical in... more ABSTRACT: At the previous conference the beginning of an extensive experimental and analytical investigation into the mechanisms leading to the initiation and propagation of damage in asphalt concrete pavements was reported. The objectives of this Asphalt Concrete Response (ACRe) project were twofold, firstly a 3-dimensional, strain rate sensitive, temperature and loading history dependent constitutive model would be formulated and implemented in the finite element package CAPA-3D. Secondly, the necessary experimental set-ups, testing procedures and data-analysis methods for determination of the model parameters would be developed. At the time the prototype formulation of the model was reported, along with preliminary test results and the way in which the model parameters were determined on the basis of the experimental results. A simulation of the dynamic non-linear response of a pavement was included to demonstrate the possibilities of the approach. In the past years, the project ...
Transportation Research Record: Journal of the Transportation Research Board, 2014
This paper describes a project that is part of NL-LAB, a larger, long-term program at Delft Unive... more This paper describes a project that is part of NL-LAB, a larger, long-term program at Delft University of Technology, Netherlands, which aims to establish the predictive capacity of the current European functional tests for Dutch asphalt concrete (AC) mixtures. In this NL-LAB program, the functional characteristics of resistance to rutting (EN 12697–25), fatigue (EN 12679-24), stiffness (EN 12697–26), and moisture sensitivity (EN 12697-12 and EN 12697–23) are determined for specimens that are (a) mixed and compacted in the lab, (b) mixed in the plant and compacted in the lab, and (c) mixed in the plant and compacted in the road. Eventually, these tests will provide insight into the effect of mixing and compaction on the functional characteristics. The project described in this paper focused on the indirect tensile strength (ITS) and the triaxial cyclic compression test for two AC mixes. The properties found for all three stages of preparation were analyzed with the use of formalisti...
Bituminous binders are known to have microstructures at typical length scales of micrometers. Thi... more Bituminous binders are known to have microstructures at typical length scales of micrometers. This microstructure can be probed with Atomic Force Microscopy (AFM). Now that worldwide several research groups are reporting AFM results on bitumen, it is becoming important to improve the understanding of the reproducibility and objectivity of the technique for studying bituminous samples. When reproducibility and stability are proven, AFM can be a tool for asphalt professionals to rapidly screen bituminous binders. In this context two independent laboratories have developed a standard method for preparing and conditioning bitumen for AFM imaging. By means of an inter-laboratory comparison of independently imaged specimen, the reproducibility of microstructure measurements was investigated. A quantitative comparison on different microstructures was developed, and the consistency of independently obtained results was confirmed. The results from both labs were comparable: the microstructural properties were found to be randomly distributed within a 5% interval. Also the influence of temperature on the microstructure was demonstrated to be reproducible and consistent. With the increase of temperature, the microstructure gradually disappeared, however traces of the microstructure remained visible up to the highest measurement temperature of 60°C. It is concluded that given well defined sample preparation and measurement procedures, the microstructure of bitumen can be reproducibly imaged by AFM from room temperature up to temperatures where bitumen has become soft and too sticky to be probed by the same setup as used for lower temperatures.
EQUATION SECTION 1 The necessity of realistic non-linear, three-dimensional material modeling for... more EQUATION SECTION 1 The necessity of realistic non-linear, three-dimensional material modeling for asphalt concrete is demonstrated by using such a model to simulate two laboratory tests. For this demonstration the Indirect Tensile Test (ITT) and Semi Circular Bending (SCB) test are used, two relatively simple tests that result in a complicated stress state in the specimen. It becomes quite clear that the observed response can not be modeled without realistic damage descriptions. Prior to these examples of model application the material model used for the simulations is presented and its suitability to describe the response of asphalt concrete is verified. This verification is based on the simulation of laboratory tests used to provide the model parameters.
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