The main objective of this study was to investigate the combined effect of the loading frequency,... more The main objective of this study was to investigate the combined effect of the loading frequency, temperature, and stress level on the fatigue life of asphalt paving mixtures. Asphalt mixtures were designed using the Superpave design procedure using a 60/70-penetration grade asphalt binder having a Superpave performance grade of PG 64-10 and crushed limestone aggregate. The indirect tension (IDT) fatigue test was used to determine the fatigue behavior of asphalt mixtures. The IDT fatigue test was conducted in the stress-controlled mode of loading using five stress levels: 288, 360, 432, 504, and 576 kPa (approximately in the range of 42–84 psi loading) representing truck or heavy traffic loadings in real-life conditions, two intermediate temperatures: 20 and 30 C, and four loading frequencies: 3, 5, 8, and 10 Hz representing truck speeds of about 12.5–45 km/h. Three replicates were used for each IDT fatigue test. A total of 120 IDT fatigue tests were conducted in this study. Findings of the study showed that the increase in loading frequency resulted in an increase in the fatigue life at the two test temperatures 20 and 30 C. In addition, the rate of increase in the fatigue life with the loading frequency was exponential, and the difference in the fatigue life (Nf) between the different loading frequencies was found to be higher at lower stress levels than that at higher strain levels at the two temperatures. It was also found that the difference in the fatigue lives between the different stress levels was much higher at higher loading frequencies than that at lower loading frequencies for both temperatures. For the stress-controlled mode of loading, which was used in this study, an increase in temperature provided shorter fatigue lives for asphalt mixtures.
The Heavy Vehicle Simulator (HVS) is ideally suited for initial calibration of Mechanistic-Empiri... more The Heavy Vehicle Simulator (HVS) is ideally suited for initial calibration of Mechanistic-Empirical models for pavement design. The HVS may be seen as a large scale laboratory equipment, with detailed control of materials, loads and environment, and with the possibility of carrying the tests through to failure. In-situ pavements, used for long term observation of pavement performance, are normally designed with a high level of reliability, resulting in very few failures within the normal service life. HVS testing may be used to close the gap between the common, small scale laboratory tests and the long term observation of in situ pavement performance. The two HVSs owned by the California Department of Transportation (Caltrans) have been used for initial calibration of the Mechanistic-Empirical models of a computer program known as CalME. CalME has an incremental-recursive procedure, making it possible to follow the gradual deterioration of the pavement during the HVS loading test. 13 new flexible pavements, with different materials and layer thicknesses, have been tested at moderate temperatures (≈ 20 ºC) and 16 sections at high temperatures (40-50 ºC). Elastic moduli were determined from Falling Weight Deflectometer (FWD) tests and from frequency sweep tests on beams in the laboratory. Fatigue parameters were determined from constant strain beam tests, and permanent deformation parameters from Repeated Simple Shear Tests at Constant Height (RSST-CH). The models derived from laboratory tests were directly used in CalME, with calibration factors to match the HVS tests. The sections tested at moderate temperature were all instrumented with Multi Depth Deflectometers (MDDs), which record both resilient and permanent deformations at several depths in the pavement structure. Surfaces deflections were also measured with a Road Surface Deflectometer (RSD, similar to a Benkelman beam) and the surface profiles were recorded by a laser profilometer. The resilient deflections changed markedly during the tests, on average the surface deflection increased by a factor of 2.4 from the beginning to end of the test. It is essential that this change in response is modeled correctly for the full duration of the test, otherwise any attempts at calibrating the empirical models would be futile. The change in response is due to the damage to the materials caused by the loads, so the validation of the response model and the calibration of the fatigue damage models for the materials are mutually dependent. Once the pavement response has been modeled correctly for the complete duration of the test, the empirical models for permanent deformation can be calibrated. The MDDs also record the permanent deformation of the individual layers in the pavement during the test. These measurements as well as the pavement surface profiles are used for calibrating the empirical models for permanent deformation at moderate temperature. The high temperature tests had relatively few load applications and were only used for calibrating the permanent deformation models of different asphalt materials.
The problem of traffic accidents is a major problem in the Hashemite Kingdom of Jordan and repres... more The problem of traffic accidents is a major problem in the Hashemite Kingdom of Jordan and represents a serious safety and economic challenge for the state. Traffic accidents are considered the second leading cause of death. This paper evaluated the impacts of the traffic policies undertaken in 2008 on traffic accidents and fatalities, including the intensification of police enforcement and implementation of traffic law with stiff penalty levels. To accomplish this objective, accidents' data of 1990 through 2009 were obtained from Jordan Traffic Institute and other related sources.
The existence of a fatigue endurance limit has been postulated for a considerable time. With the ... more The existence of a fatigue endurance limit has been postulated for a considerable time. With the increasing emphasis on extended-life hot-mix asphalt pavement, or perpetual pavement, verification of the existence of this endurance limit, a strain below which none or very little fatigue damage develops, has become a substantial consideration in the design of these new multilayered full-depth pavements. Fatigue data are presented that were collected on a surface mix and a binder mixture tested for an extended period from 5 million to 48 million load repetitions at strain levels down to 70 microstrain. The fatigue results are analyzed in the traditional manner and using the dissipated energy ratio. This analysis shows that there is a difference in the data at normal strain levels recommended for fatigue testing and at the low strain levels. This difference cannot substantiate an endurance limit using traditional analysis procedures, but the dissipated energy approach clearly shows a distinct change in material behavior at low flexural strain levels, which supports the fact that at low strain levels the damage accumulated from each load cycle is disproportionately less than what is predicted from extrapolations of fatigue testing at normal strain levels. This reduced damage may be attributed to the healing process. The conclusion of this study is that laboratory testing can verify the existence of a fatigue endurance limit in the range of 90 to 70 microstrain below which the fatigue life of the mixture is significantly extended relative to normal design considerations.
Determination of the failure limit in a repeated-load fatigue test in the laboratory has relied e... more Determination of the failure limit in a repeated-load fatigue test in the laboratory has relied entirely on the arbitrary selection of a fixed criterion. The constant strain and constant stress modes of fatigue loading have been described by a consistent definition of failure in ...
Transportation Research Record: Journal of the Transportation Research Board, 2008
The Heavy Vehicle Simulator (HVS) is ideally suited for initial calibration of Mechanistic-Empiri... more The Heavy Vehicle Simulator (HVS) is ideally suited for initial calibration of Mechanistic-Empirical models for pavement design. The HVS may be seen as a large scale laboratory equipment, with detailed control of materials, loads and environment, and with the possibility of carrying the tests through to failure. In-situ pavements, used for long term observation of pavement performance, are normally designed with a high level of reliability, resulting in very few failures within the normal service life. HVS testing may be used to close the gap between the common, small scale laboratory tests and the long term observation of in situ pavement performance. The two HVSs owned by the California Department of Transportation (Caltrans) have been used for initial calibration of the Mechanistic-Empirical models of a computer program known as CalME. CalME has an incremental-recursive procedure, making it possible to follow the gradual deterioration of the pavement during the HVS loading test. 13 new flexible pavements, with different materials and layer thicknesses, have been tested at moderate temperatures (≈ 20 ºC) and 16 sections at high temperatures (40-50 ºC). Elastic moduli were determined from Falling Weight Deflectometer (FWD) tests and from frequency sweep tests on beams in the laboratory. Fatigue parameters were determined from constant strain beam tests, and permanent deformation parameters from Repeated Simple Shear Tests at Constant Height (RSST-CH). The models derived from laboratory tests were directly used in CalME, with calibration factors to match the HVS tests. The sections tested at moderate temperature were all instrumented with Multi Depth Deflectometers (MDDs), which record both resilient and permanent deformations at several depths in the pavement structure. Surfaces deflections were also measured with a Road Surface Deflectometer (RSD, similar to a Benkelman beam) and the surface profiles were recorded by a laser profilometer. The resilient deflections changed markedly during the tests, on average the surface deflection increased by a factor of 2.4 from the beginning to end of the test. It is essential that this change in response is modeled correctly for the full duration of the test, otherwise any attempts at calibrating the empirical models would be futile. The change in response is due to the damage to the materials caused by the loads, so the validation of the response model and the calibration of the fatigue damage models for the materials are mutually dependent. Once the pavement response has been modeled correctly for the complete duration of the test, the empirical models for permanent deformation can be calibrated. The MDDs also record the permanent deformation of the individual layers in the pavement during the test. These measurements as well as the pavement surface profiles are used for calibrating the empirical models for permanent deformation at moderate temperature. The high temperature tests had relatively few load applications and were only used for calibrating the permanent deformation models of different asphalt materials.
The existence of a fatigue endurance limit has been postulated for a considerable time. With the ... more The existence of a fatigue endurance limit has been postulated for a considerable time. With the increasing emphasis on extended-life hot-mix asphalt pavement, or perpetual pavement, verification of the existence of this endurance limit, a strain below which none or very little fatigue damage develops, has become a substantial consideration in the design of these new multilayered full-depth pavements. Fatigue data are presented that were collected on a surface mix and a binder mixture tested for an extended period from 5 million to 48 million load repetitions at strain levels down to 70 microstrain. The fatigue results are analyzed in the traditional manner and using the dissipated energy ratio. This analysis shows that there is a difference in the data at normal strain levels recommended for fatigue testing and at the low strain levels. This difference cannot substantiate an endurance limit using traditional analysis procedures, but the dissipated energy approach clearly shows a distinct change in material behavior at low flexural strain levels, which supports the fact that at low strain levels the damage accumulated from each load cycle is disproportionately less than what is predicted from extrapolations of fatigue testing at normal strain levels. This reduced damage may be attributed to the healing process. The conclusion of this study is that laboratory testing can verify the existence of a fatigue endurance limit in the range of 90 to 70 microstrain below which the fatigue life of the mixture is significantly extended relative to normal design considerations.
International Journal of Pavement Engineering, 2009
... DOI: 10.1080/10298430802342773 AM Rahim a * , Gregg ... This is accomplished by cracking the ... more ... DOI: 10.1080/10298430802342773 AM Rahim a * , Gregg ... This is accomplished by cracking the concrete into smaller slabs, thus distributing the thermal-induced strains more evenly in the asphalt overlay (Al Hakim and Jennison 19991. Al Hakim, B. and Jennison, CW 1999. ...
International Journal of Pavement Engineering, 2013
Selection of proper binder is one of the most important factors considered in mixture design. Thr... more Selection of proper binder is one of the most important factors considered in mixture design. Three different asphalt grading systems are normally used; they are penetration grading system, viscosity grading system and performance grading (PG) systems. PG system is a method of measuring asphalt binder performance; it was originally developed during strategic highway research program in the early 1990s in
In 1996, California Department of Transportation ͑Caltrans͒ initiated an extensive project to dev... more In 1996, California Department of Transportation ͑Caltrans͒ initiated an extensive project to develop mechanistic-empirical ͑ME͒ pavement design and analysis tools, which will help state design engineers incorporate the impact of new products and technologies, increased traffic volumes and axle loading, and variable climatic conditions. As part of the development of new ME design procedures, Caltrans is developing a suite of dedicated software. CalME is a ME design program for flexible pavements that parallels the NCHRP 1-37A ͑MEPDG͒ and is calibrated for California conditions. CalBack is a sophisticated back-calculation program that contains specific features pertinent to California and is designed to work standalone, or in concert with CalME. CalBack is a unique and important addition to the existing knowledge base in that it possesses multiple data input/output methods, several new analytical modeling methods, and numerous user performance options. This paper describes the successful development and implementation of CalBack in three ways: ͑1͒ why and how Caltrans developed CalBack; ͑2͒ how CalBack functions; and ͑3͒ representative studies that show how well the software performs. Application of CalBack in several California projects, including the case studies presented in this paper, has shown that back-calculated moduli for different layers in the flexible and rigid pavement systems agreed reasonably well with laboratory measured values. Furthermore, the importance of avoiding temperature gradients when evaluating portland cement concrete pavements with the falling weight deflectometer is also well captured by CalBack.
Page 1. A stereometric knowledge-based system for maintenance of street networks1 Mohammed Taleb ... more Page 1. A stereometric knowledge-based system for maintenance of street networks1 Mohammed Taleb Obaidat, Turki I. Al-Suleiman, and Khalid A. Ghuzlan ... 1990; Sharaf and Abdul-Hai 1992; Kuo et al. 1992; Acosta et al. 1992). ...
The main objective of this study was to investigate the combined effect of the loading frequency,... more The main objective of this study was to investigate the combined effect of the loading frequency, temperature, and stress level on the fatigue life of asphalt paving mixtures. Asphalt mixtures were designed using the Superpave design procedure using a 60/70-penetration grade asphalt binder having a Superpave performance grade of PG 64-10 and crushed limestone aggregate. The indirect tension (IDT) fatigue test was used to determine the fatigue behavior of asphalt mixtures. The IDT fatigue test was conducted in the stress-controlled mode of loading using five stress levels: 288, 360, 432, 504, and 576 kPa (approximately in the range of 42–84 psi loading) representing truck or heavy traffic loadings in real-life conditions, two intermediate temperatures: 20 and 30 C, and four loading frequencies: 3, 5, 8, and 10 Hz representing truck speeds of about 12.5–45 km/h. Three replicates were used for each IDT fatigue test. A total of 120 IDT fatigue tests were conducted in this study. Findings of the study showed that the increase in loading frequency resulted in an increase in the fatigue life at the two test temperatures 20 and 30 C. In addition, the rate of increase in the fatigue life with the loading frequency was exponential, and the difference in the fatigue life (Nf) between the different loading frequencies was found to be higher at lower stress levels than that at higher strain levels at the two temperatures. It was also found that the difference in the fatigue lives between the different stress levels was much higher at higher loading frequencies than that at lower loading frequencies for both temperatures. For the stress-controlled mode of loading, which was used in this study, an increase in temperature provided shorter fatigue lives for asphalt mixtures.
The Heavy Vehicle Simulator (HVS) is ideally suited for initial calibration of Mechanistic-Empiri... more The Heavy Vehicle Simulator (HVS) is ideally suited for initial calibration of Mechanistic-Empirical models for pavement design. The HVS may be seen as a large scale laboratory equipment, with detailed control of materials, loads and environment, and with the possibility of carrying the tests through to failure. In-situ pavements, used for long term observation of pavement performance, are normally designed with a high level of reliability, resulting in very few failures within the normal service life. HVS testing may be used to close the gap between the common, small scale laboratory tests and the long term observation of in situ pavement performance. The two HVSs owned by the California Department of Transportation (Caltrans) have been used for initial calibration of the Mechanistic-Empirical models of a computer program known as CalME. CalME has an incremental-recursive procedure, making it possible to follow the gradual deterioration of the pavement during the HVS loading test. 13 new flexible pavements, with different materials and layer thicknesses, have been tested at moderate temperatures (≈ 20 ºC) and 16 sections at high temperatures (40-50 ºC). Elastic moduli were determined from Falling Weight Deflectometer (FWD) tests and from frequency sweep tests on beams in the laboratory. Fatigue parameters were determined from constant strain beam tests, and permanent deformation parameters from Repeated Simple Shear Tests at Constant Height (RSST-CH). The models derived from laboratory tests were directly used in CalME, with calibration factors to match the HVS tests. The sections tested at moderate temperature were all instrumented with Multi Depth Deflectometers (MDDs), which record both resilient and permanent deformations at several depths in the pavement structure. Surfaces deflections were also measured with a Road Surface Deflectometer (RSD, similar to a Benkelman beam) and the surface profiles were recorded by a laser profilometer. The resilient deflections changed markedly during the tests, on average the surface deflection increased by a factor of 2.4 from the beginning to end of the test. It is essential that this change in response is modeled correctly for the full duration of the test, otherwise any attempts at calibrating the empirical models would be futile. The change in response is due to the damage to the materials caused by the loads, so the validation of the response model and the calibration of the fatigue damage models for the materials are mutually dependent. Once the pavement response has been modeled correctly for the complete duration of the test, the empirical models for permanent deformation can be calibrated. The MDDs also record the permanent deformation of the individual layers in the pavement during the test. These measurements as well as the pavement surface profiles are used for calibrating the empirical models for permanent deformation at moderate temperature. The high temperature tests had relatively few load applications and were only used for calibrating the permanent deformation models of different asphalt materials.
The problem of traffic accidents is a major problem in the Hashemite Kingdom of Jordan and repres... more The problem of traffic accidents is a major problem in the Hashemite Kingdom of Jordan and represents a serious safety and economic challenge for the state. Traffic accidents are considered the second leading cause of death. This paper evaluated the impacts of the traffic policies undertaken in 2008 on traffic accidents and fatalities, including the intensification of police enforcement and implementation of traffic law with stiff penalty levels. To accomplish this objective, accidents' data of 1990 through 2009 were obtained from Jordan Traffic Institute and other related sources.
The existence of a fatigue endurance limit has been postulated for a considerable time. With the ... more The existence of a fatigue endurance limit has been postulated for a considerable time. With the increasing emphasis on extended-life hot-mix asphalt pavement, or perpetual pavement, verification of the existence of this endurance limit, a strain below which none or very little fatigue damage develops, has become a substantial consideration in the design of these new multilayered full-depth pavements. Fatigue data are presented that were collected on a surface mix and a binder mixture tested for an extended period from 5 million to 48 million load repetitions at strain levels down to 70 microstrain. The fatigue results are analyzed in the traditional manner and using the dissipated energy ratio. This analysis shows that there is a difference in the data at normal strain levels recommended for fatigue testing and at the low strain levels. This difference cannot substantiate an endurance limit using traditional analysis procedures, but the dissipated energy approach clearly shows a distinct change in material behavior at low flexural strain levels, which supports the fact that at low strain levels the damage accumulated from each load cycle is disproportionately less than what is predicted from extrapolations of fatigue testing at normal strain levels. This reduced damage may be attributed to the healing process. The conclusion of this study is that laboratory testing can verify the existence of a fatigue endurance limit in the range of 90 to 70 microstrain below which the fatigue life of the mixture is significantly extended relative to normal design considerations.
Determination of the failure limit in a repeated-load fatigue test in the laboratory has relied e... more Determination of the failure limit in a repeated-load fatigue test in the laboratory has relied entirely on the arbitrary selection of a fixed criterion. The constant strain and constant stress modes of fatigue loading have been described by a consistent definition of failure in ...
Transportation Research Record: Journal of the Transportation Research Board, 2008
The Heavy Vehicle Simulator (HVS) is ideally suited for initial calibration of Mechanistic-Empiri... more The Heavy Vehicle Simulator (HVS) is ideally suited for initial calibration of Mechanistic-Empirical models for pavement design. The HVS may be seen as a large scale laboratory equipment, with detailed control of materials, loads and environment, and with the possibility of carrying the tests through to failure. In-situ pavements, used for long term observation of pavement performance, are normally designed with a high level of reliability, resulting in very few failures within the normal service life. HVS testing may be used to close the gap between the common, small scale laboratory tests and the long term observation of in situ pavement performance. The two HVSs owned by the California Department of Transportation (Caltrans) have been used for initial calibration of the Mechanistic-Empirical models of a computer program known as CalME. CalME has an incremental-recursive procedure, making it possible to follow the gradual deterioration of the pavement during the HVS loading test. 13 new flexible pavements, with different materials and layer thicknesses, have been tested at moderate temperatures (≈ 20 ºC) and 16 sections at high temperatures (40-50 ºC). Elastic moduli were determined from Falling Weight Deflectometer (FWD) tests and from frequency sweep tests on beams in the laboratory. Fatigue parameters were determined from constant strain beam tests, and permanent deformation parameters from Repeated Simple Shear Tests at Constant Height (RSST-CH). The models derived from laboratory tests were directly used in CalME, with calibration factors to match the HVS tests. The sections tested at moderate temperature were all instrumented with Multi Depth Deflectometers (MDDs), which record both resilient and permanent deformations at several depths in the pavement structure. Surfaces deflections were also measured with a Road Surface Deflectometer (RSD, similar to a Benkelman beam) and the surface profiles were recorded by a laser profilometer. The resilient deflections changed markedly during the tests, on average the surface deflection increased by a factor of 2.4 from the beginning to end of the test. It is essential that this change in response is modeled correctly for the full duration of the test, otherwise any attempts at calibrating the empirical models would be futile. The change in response is due to the damage to the materials caused by the loads, so the validation of the response model and the calibration of the fatigue damage models for the materials are mutually dependent. Once the pavement response has been modeled correctly for the complete duration of the test, the empirical models for permanent deformation can be calibrated. The MDDs also record the permanent deformation of the individual layers in the pavement during the test. These measurements as well as the pavement surface profiles are used for calibrating the empirical models for permanent deformation at moderate temperature. The high temperature tests had relatively few load applications and were only used for calibrating the permanent deformation models of different asphalt materials.
The existence of a fatigue endurance limit has been postulated for a considerable time. With the ... more The existence of a fatigue endurance limit has been postulated for a considerable time. With the increasing emphasis on extended-life hot-mix asphalt pavement, or perpetual pavement, verification of the existence of this endurance limit, a strain below which none or very little fatigue damage develops, has become a substantial consideration in the design of these new multilayered full-depth pavements. Fatigue data are presented that were collected on a surface mix and a binder mixture tested for an extended period from 5 million to 48 million load repetitions at strain levels down to 70 microstrain. The fatigue results are analyzed in the traditional manner and using the dissipated energy ratio. This analysis shows that there is a difference in the data at normal strain levels recommended for fatigue testing and at the low strain levels. This difference cannot substantiate an endurance limit using traditional analysis procedures, but the dissipated energy approach clearly shows a distinct change in material behavior at low flexural strain levels, which supports the fact that at low strain levels the damage accumulated from each load cycle is disproportionately less than what is predicted from extrapolations of fatigue testing at normal strain levels. This reduced damage may be attributed to the healing process. The conclusion of this study is that laboratory testing can verify the existence of a fatigue endurance limit in the range of 90 to 70 microstrain below which the fatigue life of the mixture is significantly extended relative to normal design considerations.
International Journal of Pavement Engineering, 2009
... DOI: 10.1080/10298430802342773 AM Rahim a * , Gregg ... This is accomplished by cracking the ... more ... DOI: 10.1080/10298430802342773 AM Rahim a * , Gregg ... This is accomplished by cracking the concrete into smaller slabs, thus distributing the thermal-induced strains more evenly in the asphalt overlay (Al Hakim and Jennison 19991. Al Hakim, B. and Jennison, CW 1999. ...
International Journal of Pavement Engineering, 2013
Selection of proper binder is one of the most important factors considered in mixture design. Thr... more Selection of proper binder is one of the most important factors considered in mixture design. Three different asphalt grading systems are normally used; they are penetration grading system, viscosity grading system and performance grading (PG) systems. PG system is a method of measuring asphalt binder performance; it was originally developed during strategic highway research program in the early 1990s in
In 1996, California Department of Transportation ͑Caltrans͒ initiated an extensive project to dev... more In 1996, California Department of Transportation ͑Caltrans͒ initiated an extensive project to develop mechanistic-empirical ͑ME͒ pavement design and analysis tools, which will help state design engineers incorporate the impact of new products and technologies, increased traffic volumes and axle loading, and variable climatic conditions. As part of the development of new ME design procedures, Caltrans is developing a suite of dedicated software. CalME is a ME design program for flexible pavements that parallels the NCHRP 1-37A ͑MEPDG͒ and is calibrated for California conditions. CalBack is a sophisticated back-calculation program that contains specific features pertinent to California and is designed to work standalone, or in concert with CalME. CalBack is a unique and important addition to the existing knowledge base in that it possesses multiple data input/output methods, several new analytical modeling methods, and numerous user performance options. This paper describes the successful development and implementation of CalBack in three ways: ͑1͒ why and how Caltrans developed CalBack; ͑2͒ how CalBack functions; and ͑3͒ representative studies that show how well the software performs. Application of CalBack in several California projects, including the case studies presented in this paper, has shown that back-calculated moduli for different layers in the flexible and rigid pavement systems agreed reasonably well with laboratory measured values. Furthermore, the importance of avoiding temperature gradients when evaluating portland cement concrete pavements with the falling weight deflectometer is also well captured by CalBack.
Page 1. A stereometric knowledge-based system for maintenance of street networks1 Mohammed Taleb ... more Page 1. A stereometric knowledge-based system for maintenance of street networks1 Mohammed Taleb Obaidat, Turki I. Al-Suleiman, and Khalid A. Ghuzlan ... 1990; Sharaf and Abdul-Hai 1992; Kuo et al. 1992; Acosta et al. 1992). ...
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and stress level on the fatigue life of asphalt paving mixtures. Asphalt mixtures were designed using
the Superpave design procedure using a 60/70-penetration grade asphalt binder having a Superpave performance
grade of PG 64-10 and crushed limestone aggregate. The indirect tension (IDT) fatigue test was
used to determine the fatigue behavior of asphalt mixtures. The IDT fatigue test was conducted in the
stress-controlled mode of loading using five stress levels: 288, 360, 432, 504, and 576 kPa (approximately
in the range of 42–84 psi loading) representing truck or heavy traffic loadings in real-life conditions, two
intermediate temperatures: 20 and 30 C, and four loading frequencies: 3, 5, 8, and 10 Hz representing truck
speeds of about 12.5–45 km/h. Three replicates were used for each IDT fatigue test. A total of 120 IDT fatigue
tests were conducted in this study. Findings of the study showed that the increase in loading frequency
resulted in an increase in the fatigue life at the two test temperatures 20 and 30 C. In addition, the rate
of increase in the fatigue life with the loading frequency was exponential, and the difference in the fatigue
life (Nf) between the different loading frequencies was found to be higher at lower stress levels than that at
higher strain levels at the two temperatures. It was also found that the difference in the fatigue lives
between the different stress levels was much higher at higher loading frequencies than that at lower loading
frequencies for both temperatures. For the stress-controlled mode of loading, which was used in this study,
an increase in temperature provided shorter fatigue lives for asphalt mixtures.
and stress level on the fatigue life of asphalt paving mixtures. Asphalt mixtures were designed using
the Superpave design procedure using a 60/70-penetration grade asphalt binder having a Superpave performance
grade of PG 64-10 and crushed limestone aggregate. The indirect tension (IDT) fatigue test was
used to determine the fatigue behavior of asphalt mixtures. The IDT fatigue test was conducted in the
stress-controlled mode of loading using five stress levels: 288, 360, 432, 504, and 576 kPa (approximately
in the range of 42–84 psi loading) representing truck or heavy traffic loadings in real-life conditions, two
intermediate temperatures: 20 and 30 C, and four loading frequencies: 3, 5, 8, and 10 Hz representing truck
speeds of about 12.5–45 km/h. Three replicates were used for each IDT fatigue test. A total of 120 IDT fatigue
tests were conducted in this study. Findings of the study showed that the increase in loading frequency
resulted in an increase in the fatigue life at the two test temperatures 20 and 30 C. In addition, the rate
of increase in the fatigue life with the loading frequency was exponential, and the difference in the fatigue
life (Nf) between the different loading frequencies was found to be higher at lower stress levels than that at
higher strain levels at the two temperatures. It was also found that the difference in the fatigue lives
between the different stress levels was much higher at higher loading frequencies than that at lower loading
frequencies for both temperatures. For the stress-controlled mode of loading, which was used in this study,
an increase in temperature provided shorter fatigue lives for asphalt mixtures.