Author(s): Alavi, Z.; Hung, S.; Jones, D.; Harvey, J. | Abstract: This report describes a prelimi... more Author(s): Alavi, Z.; Hung, S.; Jones, D.; Harvey, J. | Abstract: This report describes a preliminary study that investigated the potential implications of using reclaimed rubberized asphalt pavement (R-RAP) materials as partial binder and aggregate replacement in new conventional dense-graded asphalt concrete mixes, and using reclaimed conventional asphalt pavement (RAP) materials as partial binder and aggregate replacement in new gap-graded asphalt rubber mixes. The use of rubberized hot mix asphalt (RHMA) in pavements in California has been increasing since the early 1990s. As these RHMA layers reach the end of their design lives they are being milled off and replaced with new hot mix asphalt (HMA) or new RHMA. The millings are being added to RAP stockpiles, which in turn are reused in new conventional HMA. There is no published information or experience documenting whether the use of R-RAP influences mix performance. Although Caltrans currently does not permit the use of any RAP...
This report summarizes the main findings from a project funded by the National Center for Sustain... more This report summarizes the main findings from a project funded by the National Center for Sustainable Transportation (NCST) to investigate the use of higher percentages of reclaimed asphalt pavement (RAP) and reclaimed asphalt shingles (RAS) as a replacement for a percentage of the virgin binder in new asphalt mixes. The research focused on testing procedures that do not first require chemical extraction and recovery of the asphalt binders from the RAP and RAS. Five different asphalt binders covering two performance grades and sourced from three California refineries were evaluated. The influence of two different percentages of RAP (25 and 40% by binder replacement) and one percentage of RAS (15% by binder replacement) were evaluated. The effect of a petroleum-based rejuvenating agent in selected mixes was also investigated. Based on the findings from this study, FAM mix testing is considered to be a potentially appropriate procedure for evaluating the properties of blended asphalt ...
This report summarizes the main findings from a project funded by the National Center for Sustain... more This report summarizes the main findings from a project funded by the National Center for Sustainable Transportation (NCST) to investigate the use of higher percentages of reclaimed asphalt pavement (RAP) and reclaimed asphalt shingles (RAS) as a replacement for a percentage of the virgin binder in new asphalt mixes in California. The research focused on testing procedures that do not first require chemical extraction and recovery of the age-hardened asphalt binders from the RAP and RAS. Five different asphalt binders covering two performance grades (PG 64-16 and PG 58-22) and sourced from three California refineries were evaluated in this study. The influence of two different percentages of RAP (25 and 40 percent by binder replacement) and one percentage of RAS (15 percent by binder replacement) were evaluated through partial factorial asphalt binder testing and full factorial fine aggregate matrix (FAM) mix testing. The effect of a petroleumbased rejuvenating agent added to select...
Polymer-modified bitumen binders have been dramatically used over the last decade to combat the in... more Polymer-modified bitumen binders have been dramatically used over the last decade to combat the increasing weight and volume of heavy vehicle traffic and to reduce the pavement maintenance cost. This paper provides the findings of a study performed to evaluate new polymer composites to be used in bitumen modification. The proposed polymer is an Elastomer–Plastomer Vulcanised (EPV) nanocomposite containing low-density polyethylene (LLDPE), styrene-butadiene- rubber, and a type of nano clay and a small amount of bitumen binder. An example of bitumen binder was modified with 2%, 4%, and 6% of different EPV types and the storage stability and morphology of modified binders were evaluated to select the optimum EPV type. Further rheological analyses were conducted on modified binders containing 2%, 4%, and 6% of the selected EPV. It has been found that modification of bitumen with 4% of the selected EPV resulted in increasing the stiffness and elastic properties at the range of intermediate to high in-service temperatures. The viscosity of modified binders also increased at elevated production temperatures.
Transportation Research Record: Journal of the Transportation Research Board
Oxidative aging is caused by oxygen diffusion into the binder when an asphalt pavement is exposed... more Oxidative aging is caused by oxygen diffusion into the binder when an asphalt pavement is exposed to the atmosphere. Aging can lead to increased susceptibility to pavement damage (i.e., raveling, cracking, and moisture damage). Investigation of the aging mechanism advances the understanding of these pavement distresses, and prediction of the aging progress improves structural design and prediction of pavement performance. Previous studies have proposed a dual-rate aging model that divides the aging progress into a short, fast-rate phase and a long constant phase. This paper further investigates the constant rate aging phase of unmodified, polymer modified, and asphalt rubber binders. The chemical composition (carbonyl, sulfoxide, ether, and ester) and the rheological properties (shear modulus and viscosity) changes were tracked to analyze the binder aging mechanism. As expected, the carbonyl component was found to consistently increase with aging time. The widely used aging model wi...
Transportation Research Record: Journal of the Transportation Research Board
Rubberized hot-mix asphalt (RHMA) has been widely used in construction projects by the California... more Rubberized hot-mix asphalt (RHMA) has been widely used in construction projects by the California Department of Transportation (Caltrans) for the environmental benefits of its recycled waste tires and for its improved fatigue and reflective cracking resistance. Currently, Caltrans does not permit the use of reclaimed asphalt pavement (RAP) in any gap- or open-graded rubberized asphalt mixes. However, given the cost and environmental benefits of RAP to replace portions of required virgin binder and aggregates in conventional mixes, interest is growing in the addition of some RAP to RHMA mixes as well. This study investigated concerns about this proposed practice. Three phases of laboratory testing (i.e., asphalt binder testing, fine aggregate matrix mix testing, and full-graded mix testing) were conducted to evaluate the effects of the addition of RAP into new RHMA mixes. The results indicated that the gap-graded aggregate structure of RHMA might limit the amount of RAP that could be...
Author(s): Alavi, Z.; Hung, S.; Jones, D.; Harvey, J. | Abstract: This report describes a prelimi... more Author(s): Alavi, Z.; Hung, S.; Jones, D.; Harvey, J. | Abstract: This report describes a preliminary study that investigated the potential implications of using reclaimed rubberized asphalt pavement (R-RAP) materials as partial binder and aggregate replacement in new conventional dense-graded asphalt concrete mixes, and using reclaimed conventional asphalt pavement (RAP) materials as partial binder and aggregate replacement in new gap-graded asphalt rubber mixes. The use of rubberized hot mix asphalt (RHMA) in pavements in California has been increasing since the early 1990s. As these RHMA layers reach the end of their design lives they are being milled off and replaced with new hot mix asphalt (HMA) or new RHMA. The millings are being added to RAP stockpiles, which in turn are reused in new conventional HMA. There is no published information or experience documenting whether the use of R-RAP influences mix performance. Although Caltrans currently does not permit the use of any RAP...
This report summarizes the main findings from a project funded by the National Center for Sustain... more This report summarizes the main findings from a project funded by the National Center for Sustainable Transportation (NCST) to investigate the use of higher percentages of reclaimed asphalt pavement (RAP) and reclaimed asphalt shingles (RAS) as a replacement for a percentage of the virgin binder in new asphalt mixes. The research focused on testing procedures that do not first require chemical extraction and recovery of the asphalt binders from the RAP and RAS. Five different asphalt binders covering two performance grades and sourced from three California refineries were evaluated. The influence of two different percentages of RAP (25 and 40% by binder replacement) and one percentage of RAS (15% by binder replacement) were evaluated. The effect of a petroleum-based rejuvenating agent in selected mixes was also investigated. Based on the findings from this study, FAM mix testing is considered to be a potentially appropriate procedure for evaluating the properties of blended asphalt ...
This report summarizes the main findings from a project funded by the National Center for Sustain... more This report summarizes the main findings from a project funded by the National Center for Sustainable Transportation (NCST) to investigate the use of higher percentages of reclaimed asphalt pavement (RAP) and reclaimed asphalt shingles (RAS) as a replacement for a percentage of the virgin binder in new asphalt mixes in California. The research focused on testing procedures that do not first require chemical extraction and recovery of the age-hardened asphalt binders from the RAP and RAS. Five different asphalt binders covering two performance grades (PG 64-16 and PG 58-22) and sourced from three California refineries were evaluated in this study. The influence of two different percentages of RAP (25 and 40 percent by binder replacement) and one percentage of RAS (15 percent by binder replacement) were evaluated through partial factorial asphalt binder testing and full factorial fine aggregate matrix (FAM) mix testing. The effect of a petroleumbased rejuvenating agent added to select...
Polymer-modified bitumen binders have been dramatically used over the last decade to combat the in... more Polymer-modified bitumen binders have been dramatically used over the last decade to combat the increasing weight and volume of heavy vehicle traffic and to reduce the pavement maintenance cost. This paper provides the findings of a study performed to evaluate new polymer composites to be used in bitumen modification. The proposed polymer is an Elastomer–Plastomer Vulcanised (EPV) nanocomposite containing low-density polyethylene (LLDPE), styrene-butadiene- rubber, and a type of nano clay and a small amount of bitumen binder. An example of bitumen binder was modified with 2%, 4%, and 6% of different EPV types and the storage stability and morphology of modified binders were evaluated to select the optimum EPV type. Further rheological analyses were conducted on modified binders containing 2%, 4%, and 6% of the selected EPV. It has been found that modification of bitumen with 4% of the selected EPV resulted in increasing the stiffness and elastic properties at the range of intermediate to high in-service temperatures. The viscosity of modified binders also increased at elevated production temperatures.
Transportation Research Record: Journal of the Transportation Research Board
Oxidative aging is caused by oxygen diffusion into the binder when an asphalt pavement is exposed... more Oxidative aging is caused by oxygen diffusion into the binder when an asphalt pavement is exposed to the atmosphere. Aging can lead to increased susceptibility to pavement damage (i.e., raveling, cracking, and moisture damage). Investigation of the aging mechanism advances the understanding of these pavement distresses, and prediction of the aging progress improves structural design and prediction of pavement performance. Previous studies have proposed a dual-rate aging model that divides the aging progress into a short, fast-rate phase and a long constant phase. This paper further investigates the constant rate aging phase of unmodified, polymer modified, and asphalt rubber binders. The chemical composition (carbonyl, sulfoxide, ether, and ester) and the rheological properties (shear modulus and viscosity) changes were tracked to analyze the binder aging mechanism. As expected, the carbonyl component was found to consistently increase with aging time. The widely used aging model wi...
Transportation Research Record: Journal of the Transportation Research Board
Rubberized hot-mix asphalt (RHMA) has been widely used in construction projects by the California... more Rubberized hot-mix asphalt (RHMA) has been widely used in construction projects by the California Department of Transportation (Caltrans) for the environmental benefits of its recycled waste tires and for its improved fatigue and reflective cracking resistance. Currently, Caltrans does not permit the use of reclaimed asphalt pavement (RAP) in any gap- or open-graded rubberized asphalt mixes. However, given the cost and environmental benefits of RAP to replace portions of required virgin binder and aggregates in conventional mixes, interest is growing in the addition of some RAP to RHMA mixes as well. This study investigated concerns about this proposed practice. Three phases of laboratory testing (i.e., asphalt binder testing, fine aggregate matrix mix testing, and full-graded mix testing) were conducted to evaluate the effects of the addition of RAP into new RHMA mixes. The results indicated that the gap-graded aggregate structure of RHMA might limit the amount of RAP that could be...
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