Walaa Mogawer - Academia.edu (original) (raw)
Papers by Walaa Mogawer
Transportation Research Record, 2016
Transportation Research Record, 2014
Because there is a greater emphasis on promoting sustainable materials within transportation infr... more Because there is a greater emphasis on promoting sustainable materials within transportation infrastructure, state agencies in the U.S. Northeast are investigating different strategies that will enable the use of higher percentages of recycled asphalt pavement (RAP) while not sacrificing the performance of the asphalt pavement. In particular, most state agencies in the Northeast are concerned with the fatigue and thermal cracking performance, as well as the general workability and handling of the higher-RAP-content asphalt mixtures when greater percentages are used. In conjunction with the Transportation Pooled Fund study TPF 5(230), Evaluation of Plant-Produced High-Percentage RAP Mixtures in the Northeast, three potential strategies were evaluated for incorporating higher RAP contents: using a softer asphalt binder grade to offset the stiff RAP asphalt binder, limiting the amount of RAP binder credited to the total asphalt content of the asphalt mixture, and using a performance-based specification that the high-RAP content mixture must meet for acceptance. The findings of the strategies through plant-produced mixtures, as well as case studies evaluated in detail through laboratory test procedures and analysis, are summarized. The project trials and results shown will, it is hoped, provide guidance to other agencies looking to increase the percentage of RAP used in their asphalt mixtures.
Transportation Research Record, 1997
Since 1986, FHWA has been performing accelerated pavement tests at its Pavement Testing Facility ... more Since 1986, FHWA has been performing accelerated pavement tests at its Pavement Testing Facility (PTF) located on the grounds of the Turner-Fairbank Highway Research Center. At this laboratory, FHWA uses two accelerated loading facility pavement testing machines to simulate the effects of heavy vehicle loading on full-scale test pavements. In 1992, FHWA, with help from Strategic Highway Research Program staff and contractors, started an experiment to validate selected aspects of the Superpave binder specification using accelerated pavement tests. Twelve test lanes with 48 individual test sites were constructed at the PTF in 1993. The results of accelerated pavement tests on these pavements will be used to validate the Superpave binder parameters for rutting and fatigue cracking.
Road Materials and Pavement Design, 2011
... Walaa Mogawer* — Alexander Austerman* Muhammed Emin Kutay** — Fujie Zhou*** ... The Viscoelas... more ... Walaa Mogawer* — Alexander Austerman* Muhammed Emin Kutay** — Fujie Zhou*** ... The Viscoelastic Continuum Damage (VECD) approach was based on work done by Kutay (Kutay et al., 2008) and Christensen (Christensen & Bonaquist., 2009; Christensen and Bonaquist ...
Road Materials and Pavement Design, May 12, 2020
This study aims to (1) determine an optimum amount of Reclaimed Asphalt Pavement (RAP) such that ... more This study aims to (1) determine an optimum amount of Reclaimed Asphalt Pavement (RAP) such that its addition does not adversely impact the fracture resistance of asphalt mixtures, and (2) determine the amount of RAP binder that is active in the total mix. For this purpose, the asphalt mixtures containing three RAP contents (15, 25 and 35%) and their recovered binders were characterized. The binders were subjected to the performance grading, frequency sweep, multiple stress creep and recovery (MSCR) and linear amplitude sweep (LAS) tests. The mixtures were evaluated using dynamic modulus, Hamburg Wheel Tracking (HWT), Flow Number (FN), Semi Circular Bend (SCB), and Ideal Cracking Tolerance (Ideal-CT). The blending efficiency of the RAP binder was determined using the Hirsch model. Based on the performance results and the relatively low binder content of asphalt mixtures in Qatar, it is recommended to use up to 20% RAP in asphalt mixtures.
Transportation Research Record, 2012
A high-performance thin asphalt overlay (HPThinOL) is specified as having a thickness of 1 in. or... more A high-performance thin asphalt overlay (HPThinOL) is specified as having a thickness of 1 in. or less and is used in applications requiring high levels of rutting and fatigue resistance. HPThinOLs are used as a pavement preservation strategy and are placed on pavements that have remaining structural capacity that is expected to outlive that strategy. Current specifications for HPThinOLs generally call for a polymer-modified asphalt (PMA). However, PMA binders are more expensive than unmodified asphalt binders. This expense, coupled with the higher binder content requirement generally associated with HPThinOL, could lead to an initial higher cost in relation to other pavement preservation strategies. Although the higher initial cost can be offset by incorporating high amounts of reclaimed asphalt pavement (RAP), the use of high amounts of RAP in PMA mixtures might adversely affect the mixture performance (stiffness, cracking, or workability). Warm-mix asphalt (WMA) technology may improve the workability of HPThinOL that incorporates high RAP content and PMA binders. This study evaluated the effect of PMA binders, high RAP content, and WMA technology on the stiffness, resistance to reflective cracking, moisture susceptibility, and workability of HPThinOL mixtures. PMA binders and high RAP content increased the stiffness of HPThinOL significantly; however, the use of WMA technology lowered mixture stiffness and improved workability. PMA may improve the cracking resistance, moisture susceptibility, and rutting resistance of high-RAP HPThinOL mixtures, depending on whether a WMA technology is used.
International Journal of Pavement Engineering, Apr 1, 2011
The purpose of this study was to evaluate the effect of density on the fatigue cracking and rutti... more The purpose of this study was to evaluate the effect of density on the fatigue cracking and rutting performance of hot mix asphalt mixtures. Two plant produced Superpave mixtures, 9.5 and 12.5 mm, were utilised to fabricate specimens to target density levels of 88, 91, 94 ...
This report summarizes the work completed during Phase II of the Americans with Disabilities Act ... more This report summarizes the work completed during Phase II of the Americans with Disabilities Act (ADA) compatible, soft-surfaced multi-use trail project. The Massachusetts Highway Department has selected a site for the proposed construction, and, during this phase of the project, the investigators from the University of Massachusetts, Dartmouth, have evaluated subsurface soil conditions at the site and have prepared design and construction recommendations which are included herein. The recommended trail geometry was developed during Phase I of this project, in accordance with both the American Association of State Highway and Transportation Officials (AASHTO) and ADA guidelines. In terms of construction materials, two recommended cross-sections were developed during this phase of the project. The first cross-section utilizes aggregate gradations and aggregate layer thicknesses which are routinely used for bicycle path construction. The second cross-section incorporates a geogrid at the subgrade/base aggregate interface. By stiffening the base, the geogrid should help to enhance the performance and extend the service life of the soft riding surface. Detailed construction specifications for both cross-sections are included in this report.
Multi-use soft-surfaced trails can be successfully shared by pedestrians (walkers, joggers), peop... more Multi-use soft-surfaced trails can be successfully shared by pedestrians (walkers, joggers), people with disabilities, and bicyclists, if they are thoughtfully planned and designed. Soft-surfacing has the potential to be more economical to construct than hard-surfaced trails (such as asphalt or portland cement concrete and placed block type pavements). However, functionality and longevity need not be compromised. The objectives of this study were to develop cross-sections and standard specifications for multi-use soft-surfaced trails that are compatible with the Americans with Disabilities Act (ADA) and environmentally responsible. Two cross-sections were recommended that can meet these needs. The first cross section incorporated a seal coated 10 cm (4 in.) compacted aggregate surface and a geotextile fabric. According to literature, the surface gradations should meet the American Association of State Highway and Transportation Officials (AASHTO) M-147 grading F gradations. This surface is placed over a well-compacted subbase and subgrade. The second cross section consisted of a seal coated 10 cm (4 in.) compacted cement stabilized soil. This cross section is placed over a well-compacted subgrade. Extensive laboratory testing was conducted to measure the physical properties of potential materials to be incorporated into the surface of the recommended trails. For the first cross section, the criteria for selecting an aggregate were gradations and cost. Bluestone, limestone, and trap rock were tested as potential materials for the first cross section. The limestone was disqualified because of its relative high cost. Different soils were tested and classified using the AASHTO classification system. Portland cement was mixed with different soils and the effect of the cement on the soil strength was measured using the California Bearing Ratio (CBR) test. The percent cement added was based on recommendations from previous research. The cement increased the strength of the soil tremendously. Gas chromatography was employed to investigate the environmental impact of using an emulsion in the seal coat. No measurable leaching was found. The design guidelines, including geometric, drainage, signage, and tactile edge delineation considerations, were developed using the guidelines of the ADA Accessibility Guidelines for Transportation Facilities and the AASHTO Guide for the Development of Bicycle Facilities.
The objective of this research was to develop a test protocol for the use of the rapid triaxial t... more The objective of this research was to develop a test protocol for the use of the rapid triaxial test method for use in quality control of hot mix asphalt (HMA) production. The scope of this study consisted of testing different mixes at two different temperatures and frequencies and evaluating the results. The equipment is rugged and portable, and the hardware and software are easy to handle and do not require extensive technician training. The results from this study show that modulus and phase angle values obtained from testing are sensitive to key mixture components and properties. The coefficients of variation of results obtained from tests conducted at 60 deg C and 1 Hz are low. Tests with fine graded mixes showed good correlation of dynamic stiffness parameters with rutting, and the stiffness parameters were found to be sensitive to dust to effective binder ratio. One significant advantage of using this test procedure as a regular quality control tool is that decisions can be taken on the basis of performance related parameters rather than on the basis of volumetric properties only. Considering the desirable qualities, it seems that this test method can be considered for regular use for quality control testing. However, before it is used, user agencies must test mixes using the suggested test protocol and establish target values and allowable variations.
Transportation Research Record, Jul 29, 2023
The Federal Highway Administration Targeted Overlay Pavement Solutions (TOPS) program presents in... more The Federal Highway Administration Targeted Overlay Pavement Solutions (TOPS) program presents innovative overlay solutions for both asphalt and concrete pavements. The objective of this study was to conduct a comparative evaluation of three TOPS types for asphalt pavements, namely, Asphalt Rubber Gap-Graded, Stone Matrix Asphalt and High-Performance Thin Overlay as regards performance, how they extend pavement service life, and whether they can be used interchangeably. Asphalt binders from two sources were used in each of these three TOPS types, thus, providing a total of six TOPS mixtures. All TOPS passed the mixture performance tests where the test had a State Transportation Agency (STA) specified or a preliminary criterion, and the test results indicated that all three TOPS types can be used interchangeably. More specifically, all six TOPS mixtures met the Massachusetts Department of Transportation’s TOPS pilot specification criteria for rutting, moisture damage, and intermediate-temperature cracking. They also passed the mixture performance tests for reflective cracking and raveling based on criteria established by other STAs. AASHTOWare® Pavement Mechanistic-Empirical Design predictive models for bottom-up fatigue cracking indicated that 2 in. of a TOPS mixture placed on an existing in-service pavement can extend pavement service life between 11.2 and 14 years depending on the type of TOPS and source of binder. The maximum difference in service life between the six TOPS was slightly less than 3 years, although most of them were within 2 years of each other. Furthermore, none of the three TOPS types could be chosen to be the best TOPS.
Transportation Research Record, Jul 29, 2023
The objective of this study was to develop a comprehensive balanced mix design (BMD) protocol for... more The objective of this study was to develop a comprehensive balanced mix design (BMD) protocol for a state highway agency (SHA) using one of the four approaches presented by both the National Asphalt Pavement Association (NAPA) and the American Association of State Highway and Transportation Officials (AASHTO). This comprehensive BMD was to ensure that a mixture design continues to be balanced from the mixture design phase to the production quality assurance (QA) phase. While existing publications by NAPA, AASHTO, and others provide a good initial framework for developing a BMD protocol, many important questions arise that are left for each SHA to answer when developing a comprehensive BMD protocol. This paper outlines these questions and how each of them was addressed. Also, a new approach for developing a pass/fail criterion for bottom-up fatigue cracking using AASHTOWare® pavement mechanistic-empirical design (PMED) predictive models is presented. Twenty-one SHA-approved plant-produced mixtures were obtained and tested to aid in the development of this pass/fail criterion. A similar approach as presented in this paper can be used by other SHAs. A comprehensive BMD protocol is presented at the end of this paper along with recommendations for future studies needed for further refinement.
... Title: VALIDATION OF ASPHALT BINDER AND MIXTURE TESTS THAT PREDICT RUTTING SUSCEPTIBILITY USI... more ... Title: VALIDATION OF ASPHALT BINDER AND MIXTURE TESTS THAT PREDICT RUTTING SUSCEPTIBILITY USING THE FHWA ... Highway Administration's (FHWA's) Accelerated Loading Facility (ALF) is being used to validate the Superpave binder parameter for rutting ...
The purpose of this study was to evaluate the effect of Hot Mix Asphalt (HMA) density on the over... more The purpose of this study was to evaluate the effect of Hot Mix Asphalt (HMA) density on the overall mixture performance in terms of fatigue cracking and rutting. Two plant produced Superpave mixtures, a 9.5 mm and 12.5 mm, were fabricated to target density levels of 88%, 91%, 94% and 97% of the theoretical maximum specific gravity. These specimens were then used to evaluate the mixtures’ stiffness, fatigue cracking characteristics, and rutting potential. The impact of density on mixture stiffness was evaluated by measuring the complex dynamic modulus (E*) of each mixture at varying temperatures and frequencies in the Asphalt Mixture Performance Test (AMPT) device. Fatigue cracking evaluations were completed using the beam fatigue test and the Overlay Test (OT) fatigue cracking analysis based on fracture mechanics theory. Rutting evaluations were completed using the Asphalt Pavement Analyzer (APA) and the flow number test in the AMPT device. Additionally, the Mechanistic-Empirical Design Guide (MEPDG) distress prediction equations were used to predict the mixture performance as function of density by varying the master curve data inputs at each target density level while keeping the remaining inputs constant. The E* data showed that increasing the mixtures' density increased the measured E*. Beam fatigue testing provided inconclusive trends relating HMA density to fatigue cracking potential. The OT based fatigue cracking analysis showed that the number of equivalent single axle loads (ESALs) required to reach the fatigue cracking failure criteria of 50% area cracked increased as the mixture density increased for both mixtures tested. APA and flow number testing indicated that the rutting potential of the mixtures decreased as HMA density increased. The MEPDG Level 1 analysis results showed a fatigue cracking trend similar to the OT fatigue cracking analysis based on fracture mechanics theory. Finally, the MEPDG Level 1 analysis exhibited the same rutting trends as the laboratory testing derived trends.
Transportation Research Record, Apr 12, 2022
Many aspects of balanced mix design (BMD) and performance-related quality control and quality acc... more Many aspects of balanced mix design (BMD) and performance-related quality control and quality acceptance (QC/QA) testing depend heavily on how the asphalt mixes are conditioned. There is, therefore, a critical need for practical loose mix conditioning protocols. The main objective of this study was to establish practical loose mix condition protocols for both the BMD and QC/QA phases. To develop these protocols, this paper reviewed the field performance and pavement lives of more than 200 test sections around the United States and found most of these test sections were 50-mm thick asphalt overlays where cracking is evident in 1 to 4 years. Based on this finding, the paper developed two conditioning protocols for asphalt overlays: short-term and mid-term. The short-term conditioning is intended for volumetric design, BMD rutting performance test, and QC/QA testing at asphalt plants, while the mid-term conditioning is mainly for BMD cracking performance test. A series of IDEAL cracking tests were then conducted with 13 mixes and the test results confirmed the validity of the mid-term conditioning protocol. It was also found that conditioning time affected mix cracking resistance significantly. The longer the conditioning time, the poorer the cracking resistance. When conditioned too long, the normalized cracking resistance difference among various mixes diminished. For asphalt mix composition, binder source (or quality) and asphalt absorption are two significant factors affecting the normalized cracking resistance of asphalt mixes; in contrast, mix type, asphalt binder content, and the use of rejuvenator had insignificant influence.
Association of Asphalt Paving Technologists Proc, 2000
The primary objective of this study was to use pavement rutting data provided by an Accelerated L... more The primary objective of this study was to use pavement rutting data provided by an Accelerated Loading Facility (ALF) to validate the Superpave asphalt binder parameter for rutting, namely G*/sind, and the Superpave 2.20-kPa criterion used to grade asphalt binders. A second objective was to determine if laboratory wheel-tracking devices for rutting provided the same conclusions as the ALF. Twelve full-scale pavements were constructed at the Federal Highway Administration's Pavement Testing Facility in McLean, VA to perform this study. Five asphalt binders, including two polymer modified asphalt binders, were used. For the three unmodified asphalt binders, the relationship between G*/sind and ALF pavement rutting performance at various test temperatures showed that a minimum allowable G*/sind of 4.40 kPa would eliminate the poorest performing mixtures. This is considered consistent with the current specification. An increase of one high-temperature Performance Grade (PG) is recommended for the ALF traffic level. This increase in PG is equivalent to changing the current minimum criterion of 2.20 kPa to 4.40 kPa. Thus, the data provided by three laboratory wheel-tracking tests also indicated that the 2.20-kPa criterion is valid. The ALF and the wheel-tracking devices showed that the parameter G*/sind was not valid for one or both of the modified binders. No other asphalt binder property provided a better relationship with ALF pavement performance for these binders.
Transportation Research Record, 2016
Transportation Research Record, 2014
Because there is a greater emphasis on promoting sustainable materials within transportation infr... more Because there is a greater emphasis on promoting sustainable materials within transportation infrastructure, state agencies in the U.S. Northeast are investigating different strategies that will enable the use of higher percentages of recycled asphalt pavement (RAP) while not sacrificing the performance of the asphalt pavement. In particular, most state agencies in the Northeast are concerned with the fatigue and thermal cracking performance, as well as the general workability and handling of the higher-RAP-content asphalt mixtures when greater percentages are used. In conjunction with the Transportation Pooled Fund study TPF 5(230), Evaluation of Plant-Produced High-Percentage RAP Mixtures in the Northeast, three potential strategies were evaluated for incorporating higher RAP contents: using a softer asphalt binder grade to offset the stiff RAP asphalt binder, limiting the amount of RAP binder credited to the total asphalt content of the asphalt mixture, and using a performance-based specification that the high-RAP content mixture must meet for acceptance. The findings of the strategies through plant-produced mixtures, as well as case studies evaluated in detail through laboratory test procedures and analysis, are summarized. The project trials and results shown will, it is hoped, provide guidance to other agencies looking to increase the percentage of RAP used in their asphalt mixtures.
Transportation Research Record, 1997
Since 1986, FHWA has been performing accelerated pavement tests at its Pavement Testing Facility ... more Since 1986, FHWA has been performing accelerated pavement tests at its Pavement Testing Facility (PTF) located on the grounds of the Turner-Fairbank Highway Research Center. At this laboratory, FHWA uses two accelerated loading facility pavement testing machines to simulate the effects of heavy vehicle loading on full-scale test pavements. In 1992, FHWA, with help from Strategic Highway Research Program staff and contractors, started an experiment to validate selected aspects of the Superpave binder specification using accelerated pavement tests. Twelve test lanes with 48 individual test sites were constructed at the PTF in 1993. The results of accelerated pavement tests on these pavements will be used to validate the Superpave binder parameters for rutting and fatigue cracking.
Road Materials and Pavement Design, 2011
... Walaa Mogawer* — Alexander Austerman* Muhammed Emin Kutay** — Fujie Zhou*** ... The Viscoelas... more ... Walaa Mogawer* — Alexander Austerman* Muhammed Emin Kutay** — Fujie Zhou*** ... The Viscoelastic Continuum Damage (VECD) approach was based on work done by Kutay (Kutay et al., 2008) and Christensen (Christensen & Bonaquist., 2009; Christensen and Bonaquist ...
Road Materials and Pavement Design, May 12, 2020
This study aims to (1) determine an optimum amount of Reclaimed Asphalt Pavement (RAP) such that ... more This study aims to (1) determine an optimum amount of Reclaimed Asphalt Pavement (RAP) such that its addition does not adversely impact the fracture resistance of asphalt mixtures, and (2) determine the amount of RAP binder that is active in the total mix. For this purpose, the asphalt mixtures containing three RAP contents (15, 25 and 35%) and their recovered binders were characterized. The binders were subjected to the performance grading, frequency sweep, multiple stress creep and recovery (MSCR) and linear amplitude sweep (LAS) tests. The mixtures were evaluated using dynamic modulus, Hamburg Wheel Tracking (HWT), Flow Number (FN), Semi Circular Bend (SCB), and Ideal Cracking Tolerance (Ideal-CT). The blending efficiency of the RAP binder was determined using the Hirsch model. Based on the performance results and the relatively low binder content of asphalt mixtures in Qatar, it is recommended to use up to 20% RAP in asphalt mixtures.
Transportation Research Record, 2012
A high-performance thin asphalt overlay (HPThinOL) is specified as having a thickness of 1 in. or... more A high-performance thin asphalt overlay (HPThinOL) is specified as having a thickness of 1 in. or less and is used in applications requiring high levels of rutting and fatigue resistance. HPThinOLs are used as a pavement preservation strategy and are placed on pavements that have remaining structural capacity that is expected to outlive that strategy. Current specifications for HPThinOLs generally call for a polymer-modified asphalt (PMA). However, PMA binders are more expensive than unmodified asphalt binders. This expense, coupled with the higher binder content requirement generally associated with HPThinOL, could lead to an initial higher cost in relation to other pavement preservation strategies. Although the higher initial cost can be offset by incorporating high amounts of reclaimed asphalt pavement (RAP), the use of high amounts of RAP in PMA mixtures might adversely affect the mixture performance (stiffness, cracking, or workability). Warm-mix asphalt (WMA) technology may improve the workability of HPThinOL that incorporates high RAP content and PMA binders. This study evaluated the effect of PMA binders, high RAP content, and WMA technology on the stiffness, resistance to reflective cracking, moisture susceptibility, and workability of HPThinOL mixtures. PMA binders and high RAP content increased the stiffness of HPThinOL significantly; however, the use of WMA technology lowered mixture stiffness and improved workability. PMA may improve the cracking resistance, moisture susceptibility, and rutting resistance of high-RAP HPThinOL mixtures, depending on whether a WMA technology is used.
International Journal of Pavement Engineering, Apr 1, 2011
The purpose of this study was to evaluate the effect of density on the fatigue cracking and rutti... more The purpose of this study was to evaluate the effect of density on the fatigue cracking and rutting performance of hot mix asphalt mixtures. Two plant produced Superpave mixtures, 9.5 and 12.5 mm, were utilised to fabricate specimens to target density levels of 88, 91, 94 ...
This report summarizes the work completed during Phase II of the Americans with Disabilities Act ... more This report summarizes the work completed during Phase II of the Americans with Disabilities Act (ADA) compatible, soft-surfaced multi-use trail project. The Massachusetts Highway Department has selected a site for the proposed construction, and, during this phase of the project, the investigators from the University of Massachusetts, Dartmouth, have evaluated subsurface soil conditions at the site and have prepared design and construction recommendations which are included herein. The recommended trail geometry was developed during Phase I of this project, in accordance with both the American Association of State Highway and Transportation Officials (AASHTO) and ADA guidelines. In terms of construction materials, two recommended cross-sections were developed during this phase of the project. The first cross-section utilizes aggregate gradations and aggregate layer thicknesses which are routinely used for bicycle path construction. The second cross-section incorporates a geogrid at the subgrade/base aggregate interface. By stiffening the base, the geogrid should help to enhance the performance and extend the service life of the soft riding surface. Detailed construction specifications for both cross-sections are included in this report.
Multi-use soft-surfaced trails can be successfully shared by pedestrians (walkers, joggers), peop... more Multi-use soft-surfaced trails can be successfully shared by pedestrians (walkers, joggers), people with disabilities, and bicyclists, if they are thoughtfully planned and designed. Soft-surfacing has the potential to be more economical to construct than hard-surfaced trails (such as asphalt or portland cement concrete and placed block type pavements). However, functionality and longevity need not be compromised. The objectives of this study were to develop cross-sections and standard specifications for multi-use soft-surfaced trails that are compatible with the Americans with Disabilities Act (ADA) and environmentally responsible. Two cross-sections were recommended that can meet these needs. The first cross section incorporated a seal coated 10 cm (4 in.) compacted aggregate surface and a geotextile fabric. According to literature, the surface gradations should meet the American Association of State Highway and Transportation Officials (AASHTO) M-147 grading F gradations. This surface is placed over a well-compacted subbase and subgrade. The second cross section consisted of a seal coated 10 cm (4 in.) compacted cement stabilized soil. This cross section is placed over a well-compacted subgrade. Extensive laboratory testing was conducted to measure the physical properties of potential materials to be incorporated into the surface of the recommended trails. For the first cross section, the criteria for selecting an aggregate were gradations and cost. Bluestone, limestone, and trap rock were tested as potential materials for the first cross section. The limestone was disqualified because of its relative high cost. Different soils were tested and classified using the AASHTO classification system. Portland cement was mixed with different soils and the effect of the cement on the soil strength was measured using the California Bearing Ratio (CBR) test. The percent cement added was based on recommendations from previous research. The cement increased the strength of the soil tremendously. Gas chromatography was employed to investigate the environmental impact of using an emulsion in the seal coat. No measurable leaching was found. The design guidelines, including geometric, drainage, signage, and tactile edge delineation considerations, were developed using the guidelines of the ADA Accessibility Guidelines for Transportation Facilities and the AASHTO Guide for the Development of Bicycle Facilities.
The objective of this research was to develop a test protocol for the use of the rapid triaxial t... more The objective of this research was to develop a test protocol for the use of the rapid triaxial test method for use in quality control of hot mix asphalt (HMA) production. The scope of this study consisted of testing different mixes at two different temperatures and frequencies and evaluating the results. The equipment is rugged and portable, and the hardware and software are easy to handle and do not require extensive technician training. The results from this study show that modulus and phase angle values obtained from testing are sensitive to key mixture components and properties. The coefficients of variation of results obtained from tests conducted at 60 deg C and 1 Hz are low. Tests with fine graded mixes showed good correlation of dynamic stiffness parameters with rutting, and the stiffness parameters were found to be sensitive to dust to effective binder ratio. One significant advantage of using this test procedure as a regular quality control tool is that decisions can be taken on the basis of performance related parameters rather than on the basis of volumetric properties only. Considering the desirable qualities, it seems that this test method can be considered for regular use for quality control testing. However, before it is used, user agencies must test mixes using the suggested test protocol and establish target values and allowable variations.
Transportation Research Record, Jul 29, 2023
The Federal Highway Administration Targeted Overlay Pavement Solutions (TOPS) program presents in... more The Federal Highway Administration Targeted Overlay Pavement Solutions (TOPS) program presents innovative overlay solutions for both asphalt and concrete pavements. The objective of this study was to conduct a comparative evaluation of three TOPS types for asphalt pavements, namely, Asphalt Rubber Gap-Graded, Stone Matrix Asphalt and High-Performance Thin Overlay as regards performance, how they extend pavement service life, and whether they can be used interchangeably. Asphalt binders from two sources were used in each of these three TOPS types, thus, providing a total of six TOPS mixtures. All TOPS passed the mixture performance tests where the test had a State Transportation Agency (STA) specified or a preliminary criterion, and the test results indicated that all three TOPS types can be used interchangeably. More specifically, all six TOPS mixtures met the Massachusetts Department of Transportation’s TOPS pilot specification criteria for rutting, moisture damage, and intermediate-temperature cracking. They also passed the mixture performance tests for reflective cracking and raveling based on criteria established by other STAs. AASHTOWare® Pavement Mechanistic-Empirical Design predictive models for bottom-up fatigue cracking indicated that 2 in. of a TOPS mixture placed on an existing in-service pavement can extend pavement service life between 11.2 and 14 years depending on the type of TOPS and source of binder. The maximum difference in service life between the six TOPS was slightly less than 3 years, although most of them were within 2 years of each other. Furthermore, none of the three TOPS types could be chosen to be the best TOPS.
Transportation Research Record, Jul 29, 2023
The objective of this study was to develop a comprehensive balanced mix design (BMD) protocol for... more The objective of this study was to develop a comprehensive balanced mix design (BMD) protocol for a state highway agency (SHA) using one of the four approaches presented by both the National Asphalt Pavement Association (NAPA) and the American Association of State Highway and Transportation Officials (AASHTO). This comprehensive BMD was to ensure that a mixture design continues to be balanced from the mixture design phase to the production quality assurance (QA) phase. While existing publications by NAPA, AASHTO, and others provide a good initial framework for developing a BMD protocol, many important questions arise that are left for each SHA to answer when developing a comprehensive BMD protocol. This paper outlines these questions and how each of them was addressed. Also, a new approach for developing a pass/fail criterion for bottom-up fatigue cracking using AASHTOWare® pavement mechanistic-empirical design (PMED) predictive models is presented. Twenty-one SHA-approved plant-produced mixtures were obtained and tested to aid in the development of this pass/fail criterion. A similar approach as presented in this paper can be used by other SHAs. A comprehensive BMD protocol is presented at the end of this paper along with recommendations for future studies needed for further refinement.
... Title: VALIDATION OF ASPHALT BINDER AND MIXTURE TESTS THAT PREDICT RUTTING SUSCEPTIBILITY USI... more ... Title: VALIDATION OF ASPHALT BINDER AND MIXTURE TESTS THAT PREDICT RUTTING SUSCEPTIBILITY USING THE FHWA ... Highway Administration's (FHWA's) Accelerated Loading Facility (ALF) is being used to validate the Superpave binder parameter for rutting ...
The purpose of this study was to evaluate the effect of Hot Mix Asphalt (HMA) density on the over... more The purpose of this study was to evaluate the effect of Hot Mix Asphalt (HMA) density on the overall mixture performance in terms of fatigue cracking and rutting. Two plant produced Superpave mixtures, a 9.5 mm and 12.5 mm, were fabricated to target density levels of 88%, 91%, 94% and 97% of the theoretical maximum specific gravity. These specimens were then used to evaluate the mixtures’ stiffness, fatigue cracking characteristics, and rutting potential. The impact of density on mixture stiffness was evaluated by measuring the complex dynamic modulus (E*) of each mixture at varying temperatures and frequencies in the Asphalt Mixture Performance Test (AMPT) device. Fatigue cracking evaluations were completed using the beam fatigue test and the Overlay Test (OT) fatigue cracking analysis based on fracture mechanics theory. Rutting evaluations were completed using the Asphalt Pavement Analyzer (APA) and the flow number test in the AMPT device. Additionally, the Mechanistic-Empirical Design Guide (MEPDG) distress prediction equations were used to predict the mixture performance as function of density by varying the master curve data inputs at each target density level while keeping the remaining inputs constant. The E* data showed that increasing the mixtures' density increased the measured E*. Beam fatigue testing provided inconclusive trends relating HMA density to fatigue cracking potential. The OT based fatigue cracking analysis showed that the number of equivalent single axle loads (ESALs) required to reach the fatigue cracking failure criteria of 50% area cracked increased as the mixture density increased for both mixtures tested. APA and flow number testing indicated that the rutting potential of the mixtures decreased as HMA density increased. The MEPDG Level 1 analysis results showed a fatigue cracking trend similar to the OT fatigue cracking analysis based on fracture mechanics theory. Finally, the MEPDG Level 1 analysis exhibited the same rutting trends as the laboratory testing derived trends.
Transportation Research Record, Apr 12, 2022
Many aspects of balanced mix design (BMD) and performance-related quality control and quality acc... more Many aspects of balanced mix design (BMD) and performance-related quality control and quality acceptance (QC/QA) testing depend heavily on how the asphalt mixes are conditioned. There is, therefore, a critical need for practical loose mix conditioning protocols. The main objective of this study was to establish practical loose mix condition protocols for both the BMD and QC/QA phases. To develop these protocols, this paper reviewed the field performance and pavement lives of more than 200 test sections around the United States and found most of these test sections were 50-mm thick asphalt overlays where cracking is evident in 1 to 4 years. Based on this finding, the paper developed two conditioning protocols for asphalt overlays: short-term and mid-term. The short-term conditioning is intended for volumetric design, BMD rutting performance test, and QC/QA testing at asphalt plants, while the mid-term conditioning is mainly for BMD cracking performance test. A series of IDEAL cracking tests were then conducted with 13 mixes and the test results confirmed the validity of the mid-term conditioning protocol. It was also found that conditioning time affected mix cracking resistance significantly. The longer the conditioning time, the poorer the cracking resistance. When conditioned too long, the normalized cracking resistance difference among various mixes diminished. For asphalt mix composition, binder source (or quality) and asphalt absorption are two significant factors affecting the normalized cracking resistance of asphalt mixes; in contrast, mix type, asphalt binder content, and the use of rejuvenator had insignificant influence.
Association of Asphalt Paving Technologists Proc, 2000
The primary objective of this study was to use pavement rutting data provided by an Accelerated L... more The primary objective of this study was to use pavement rutting data provided by an Accelerated Loading Facility (ALF) to validate the Superpave asphalt binder parameter for rutting, namely G*/sind, and the Superpave 2.20-kPa criterion used to grade asphalt binders. A second objective was to determine if laboratory wheel-tracking devices for rutting provided the same conclusions as the ALF. Twelve full-scale pavements were constructed at the Federal Highway Administration's Pavement Testing Facility in McLean, VA to perform this study. Five asphalt binders, including two polymer modified asphalt binders, were used. For the three unmodified asphalt binders, the relationship between G*/sind and ALF pavement rutting performance at various test temperatures showed that a minimum allowable G*/sind of 4.40 kPa would eliminate the poorest performing mixtures. This is considered consistent with the current specification. An increase of one high-temperature Performance Grade (PG) is recommended for the ALF traffic level. This increase in PG is equivalent to changing the current minimum criterion of 2.20 kPa to 4.40 kPa. Thus, the data provided by three laboratory wheel-tracking tests also indicated that the 2.20-kPa criterion is valid. The ALF and the wheel-tracking devices showed that the parameter G*/sind was not valid for one or both of the modified binders. No other asphalt binder property provided a better relationship with ALF pavement performance for these binders.