The Experts below are selected from a list of 28140 Experts worldwide ranked by ideXlab platform
Reynaldo Roque - One of the best experts on this subject based on the ideXlab platform.
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Cracking Performance characterisation of asphalt mixtures containing reclaimed asphalt pavement with hybrid binder
2019Co-Authors: Yu Yan, Reynaldo Roque, David Hernando, Sanghyun ChunAbstract:This study investigated the effect of reclaimed asphalt pavement (RAP) on the rheological properties of a hybrid binder and the fracture properties and Cracking Performance of resultant mixtures. F...
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Cracking Performance characterisation of asphalt mixtures containing reclaimed asphalt pavement with hybrid binder
2019Co-Authors: Reynaldo Roque, David Hernando, Sanghyu ChuAbstract:This study investigated the effect of reclaimed asphalt pavement (RAP) on the rheological properties of a hybrid binder and the fracture properties and Cracking Performance of resultant mixtures. Fracture properties of the same mixtures containing up to 40% RAP with a standard polymer-modified asphalt (PMA) binder were used as benchmarks. RAP mixtures with hybrid binder exhibited lower resilient modulus, higher failure strain and higher fracture energy density than PMA RAP mixtures. Results indicated that rubber particles might not dissolve in the base binder; therefore, hybrid binder had more “free” soft binder to blend with the RAP whereas the more integrated polymer network present in PMA binder resulted in stiffer mixtures. Furthermore, PMA RAP mixtures exhibited lower damage accumulation rate than hybrid RAP mixtures. Eventually, hybrid and PMA RAP mixtures yielded comparable energy ratio values, which indicate both binder types can be interchangeably used in mixtures with up to 40% RAP for satisfact...
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evaluation of Cracking Performance for polymer modified asphalt mixtures with high rap content
2017Co-Authors: Reynaldo Roque, Cristian Cocconcelli, Michael Bekoe, George LoppAbstract:Fourteen reclaimed asphalt pavement (RAP) mixtures designed with different combinations of RAP sources, contents (up to 40%) and mixture conditioning levels were evaluated to determine the maximum allowable amount of RAP material in surface courses without jeopardising pavement Cracking Performance. Extracted RAP binder was blended with virgin polymer-modified asphalt (PMA) binder at various RAP binder replacement ratios. All blends behaved effectively as PMA binder as they met the multiple stress creep recovery (MSCR) %recovery requirement, and in addition they had satisfactory binder fracture energy density values. RAP gradation was found to significantly affect the fracture properties of RAP mixtures as it controls the distribution of RAP binder and potentially the degree of blending between virgin and RAP binder. Increased RAP content resulted in stronger (i.e. higher tensile strength) but more brittle (i.e. lower failure strain and lower mixture fracture energy) mixtures. However, after long-term ove...
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impact of hydrated lime on Cracking Performance of asphalt mixtures with oxidation and cyclic pore pressure
2016Co-Authors: Reynaldo Roque, George Lopp, Marco Isola, Michael BekoeAbstract:This research was conducted to evaluate the impact of hydrated lime (HL) on the Cracking Performance of asphalt mixtures for a broad range of aggregate types, including granites and limestones. A recently developed conditioning procedure, long-term oven aging (LTOA) plus cyclic pore pressure conditioning (CPPC), was employed to simulate the effects of long-term field aging on asphalt mixtures. The energy ratio (ER) approach, which took into account mixture properties that were known to be closely related to Cracking and was calibrated with cores taken from field-aged pavements throughout Florida, was used to evaluate the Cracking Performance of untreated and lime-treated mixtures. The results show that the introduction of HL appeared to mitigate the detrimental effects of oxidative aging and moisture (LTOA plus CPPC) on the damage and fracture-related properties of granite and limestone mixtures. This effect resulted in better Cracking Performance of these mixtures. Further analysis based on comparison of...
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effects of alternative polymer modifications on Cracking Performance of asphalt binders and resultant mixtures
2016Co-Authors: Yu Yan, Sanghyun Chun, Reynaldo Roque, Sungho KimAbstract:Abstract The use of styrene-butadiene-styrene (SBS) polymer-modified asphalt (PMA) binder has successfully enhanced pavement Cracking Performance. Meanwhile, state agencies hesitate to allow the use of alternative PMA binders that meeting existing specification requirements for PG 76-22 SBS PMA binder, due to a lack of experience and documented Performance. A previous study identified four out of seven alternative PMA binders that exhibited excellent elastomeric behavior and fracture properties. This study extends these prior efforts by assessing whether binder results translate to improved Cracking Performance of resultant mixtures. Superpave indirect tension (IDT) tests were conducted to obtain the fracture properties of asphalt mixtures with the four alternative PMA binders, as well as a standard PG 76-22 (3% SBS) PMA binder and a PG 67-22 unmodified base binder. Results showed that these alternative PMA binders, produced with SBS plus polypropylene composite, terpolymer plus polypropylene composite, SBS plus oxidized polyethylene wax and a fourth non-SBS polymer of unknown composition, not only reduced the rate of damage accumulation but also improved the failure limit of the resultant mixtures. The energy ratio (ER) parameter which has been closely tied to field pavement Cracking Performance was calculated for each mixture, and the results showed that these alternative PMA binder exhibited equivalent or better Cracking Performance than the PG 76-22 SBS PMA binder. Finally, the binder fracture energy density (FED) results satisfactorily rank mixture Cracking Performance thereby supporting the use of the binder fracture energy (BFE) test as an effective tool to quantitatively evaluate the relatively Cracking Performance of asphalt binder.
Nicola S Heckeberg - One of the best experts on this subject based on the ideXlab platform.
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testing the influence of crushing surface variation on seed Cracking Performance among beak morphs of the african seedcracker pyrenestes ostrinus
2021Co-Authors: Nicola S Heckeberg, Philip S L Anderson, Emily J RayfieldAbstract:Extreme phenotypic polymorphism is an oft-cited example of evolutionary theory in practise. Although these morphological variations are assumed to be adaptive, few studies have biomechanically tested such hypotheses. Pyrenestes ostrinus (the African seedcracker finch) shows an intraspecific polymorphism in beak size and shape that is entirely diet driven and allelically determined. Three distinct morphs feed upon soft sedge seeds during times of abundance, but switch to specializing on three different species of sedge seeds that differ significantly in hardness during lean times. Here we test the hypothesis that beak morphology is directly related to consuming seeds of different hardness. We used a novel experimental analysis to test how beak morphology affects the efficiency of Cracking sedge seeds of variable hardness. We found that neither mandibular ramus width nor crushing surface morphology had significant effects on the ability to crack different seed types. It is likely that feeding Performance is correlated with other aspects of beak size and shape such as beak depth and strength, muscle force, or gape. Our results highlight how even seemingly straightforward examples of adaptive selection in nature can be complex in practice.
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testing the influence of crushing surface variation on seed Cracking Performance between beak morphs of the african seedcracker pyrenestes ostrinus
2021Co-Authors: Nicola S Heckeberg, Philip S L Anderson, Emily J RayfieldAbstract:Extreme phenotypic polymorphism is an oft-cited example of evolutionary theory in practise. Although these morphological variations are assumed to be adaptive, few studies have biomechanically tested such hypotheses. Pyrenestes ostrinus (the African seedcracker finch) shows an intraspecific polymorphism in beak size and shape that is entirely diet driven and allelically determined. Three distinct morphs feed upon soft sedge seeds during times of abundance, but switch to specializing on three different species of sedge seeds that differ significantly in hardness during lean times. Here we test the hypothesis that beak morphology is directly related to consuming seeds of different hardness. We used a novel experimental analysis to test how beak morphology affects the efficiency of Cracking sedge seeds of variable hardness. We found that neither mandibular ramus width nor crushing surface morphology had significant effects on the ability to crack different seed types. It is likely that feeding Performance is correlated with other aspects of beak size and shape such as beak depth and strength, muscle force, or gape. Our results highlight how even seemingly straightforward examples of adaptive selection in nature can be complex in practice.
Eshan V. Dave - One of the best experts on this subject based on the ideXlab platform.
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asphalt mix fracture energy based reflective Cracking Performance criteria for overlay mix selection and design for pavements in cold climates
2019Co-Authors: Mirkat Oshone, Eshan V. Dave, Jo E SiasAbstract:Abstract This study investigates the dependence of overlay field Cracking Performance on overlay thickness and fracture energy of asphalt mixture. A total of 15 pavement sections in Minnesota for which Disk-shape Compact Tension (DCT) testing was performed on field cores from overlays were used for the study. Due to the difference in the overlay lives, different Cracking Performance measures such as average transverse Cracking rate (ATCR), maximum transverse Cracking rate (MTCR) and transverse Cracking Performance index (TCTotal) were calculated. These Cracking Performance measures were compared with asphalt overlay thicknesses and DCT fracture energies. The analysis indicated the dependence of TCTotal on both overlay thickness and fracture energy. The observed relationship was assessed for reliability using a statistical analysis and a new Performance parameter that combines overlay thickness with fracture energy is proposed to provide measure of total fracture resistance of the overlay. Preliminary thresholds are also proposed for selection of overlay thicknesses and material types in new overlays.
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effects of mix design and fracture energy on transverse Cracking Performance of asphalt pavements in minnesota
2016Co-Authors: Eshan V. Dave, Chelsea Hoplin, Benjamin Helmer, Jay Dailey, David A Van Deusen, Jerry Geib, Luke JohanneckAbstract:Asphalt pavements in colder climates encounter significantly shortened service lives because of excessive transverse Cracking. This paper presents the results for 26 pavement sections in Minnesota that were studied to evaluate the effects of asphalt mix designs on pavement Cracking Performance. The field Performance is presented with various Cracking measures and compared with mix design aspects such as amount of asphalt binder, binder grade, and amount of recycling. The disk-shaped compact tension (DCT) fracture energies measured on the field cored samples are also compared with Cracking Performance. In this study, asphalt pavement sections from several locations were evaluated to encompass various types of asphalt mixtures and asphalt construction types that were commonly used in Minnesota. The amount of transverse Cracking for each section was converted into a newly proposed Cracking Performance measure that accounted for the amount, rate, and timing of Cracking. The comparisons between asphalt mixture...
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implementation of laboratory testing to predict low temperature Cracking Performance of asphalt pavements
2016Co-Authors: Eshan V. Dave, Benjamin Helmer, Chelsea Hanson, Jared Munch, Luke JohanneckAbstract:In cold climate regions, thermal Cracking of asphalt pavements is a major pavement distress. Cold climates cause a thermal contraction within the pavement. When combined with the brittle behaviour of asphalt at low temperatures, the thermally induced stresses are relieved by transverse cracks forming in the pavement. This Cracking facilitates poor ride quality and premature failure of the pavement. There is currently no asphalt mixture Performance test required by majority of Department of Transportations (DOTs) in the United States to address the issue of thermal Cracking. Previous research has indicated that fracture energy of asphalt mixtures is a reliable predictor of transverse Cracking Performance. This mechanistic property of asphalt mixtures can be found using the disk-shaped compact tension (DCT) test. On basis of previous research, a low-temperature Cracking Performance specification that uses DCT fracture energy has been developed. During 2013 construction season, five construction projects were chosen to implement provisional specifications that use fracture energy as a required mix parameter. The projects encompassed different construction techniques, material compositions and climatic zones. The implementation procedure as well as the results from testing is presented in this paper. The results indicate a shift in the DCT fracture energy values between laboratory produced specimens that were provided as part of mix design acceptance and those manufactured using plant produced mix. Other findings include reaffirmation of common knowledge that use of higher binder contents and/or improved low temperature binder grades provide mixtures with improved fracture energies.
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flexible pavement thermal Cracking Performance sensitivity to fracture energy variation of asphalt mixtures
2015Co-Authors: Eshan V. Dave, Chelsea HoplinAbstract:Thermal Cracking in asphalt pavements continues to be a significant pavement distress mechanism in cold climate regions. The formation of discontinuities due to thermal Cracking causes extensive damage to the integrity of the pavement and forms pathways for intrusion of water into the base and subgrade layers. Current use of the Performance-based binder specifications has not been shown to effectively lower the propensity for this distress. When this is combined with advent of newer asphalt mix manufacturing and construction technologies as well as desire for incorporation of greater amounts of recycled materials in paving mixtures, it has led to significant research and implementation efforts on asphalt mixture Performance-based specifications. On the basis of various past research studies on low temperature Cracking, a Performance specification that utilises fracture energy of asphalt mixtures through use of disk-shaped compact tension (DCT) test has been developed. A significant number of present studi...
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thermal Cracking Performance prediction and asset management integration
2011Co-Authors: William G Buttlar, Eshan V. Dave, Glaucio H Paulino, Sofie E. LeonAbstract:With shrinking maintenance budgets and the need to ‘do more with less,’ accurate, robust asset management tools are greatly needed for the transportation engineering community. In addition, the increased use of recycled materials and low energy production techniques such as warm-mix asphalt are leading to increased needs for preventive and rehabilitative maintenance activities. The timing of such activities will greatly affect the total discounted life-cycle cost of the pavement system. Low-temperature Cracking of hot-mix asphalt (HMA) pavements continues to be a leading cause of premature pavement deterioration in regions of cold climate and/or where significant thermal cycling occurs. Recent advances in fracture testing and modeling of hot-mix asphalt (HMA) materials have greatly aided in the understanding of the key mechanisms behind this important pavement distress, which can greatly reduce pavement lifespan and the lifespan of subsequent rehabilitation cycles. However, there is a need for implementation of new models into a standalone program which can be readily utilized by researchers and practitioners. Moreover, the complete integration of material selection, material design, pavement design and pavement Performance into a more holistic asset management system has been hampered by the lack of accurate, user-friendly Performance prediction models for pavements. The objective of this project was to complete the development of a user-friendly interface that provides simplified access to sophisticated low-temperature Cracking prediction models. This stand-alone program will greatly accelerate the transfer of this technology to practitioners and other interested scientists and engineers (pavement designers, analysts, and researchers). The program is designed to be compatible with the existing thermal Cracking model used in the Mechanistic Empirical Pavement Design Guide (MEPDG), and with the new thermal Cracking model being developed under the National Pooled Fund Study on Low Temperature Cracking. As part of this report, the key developments associated with the new mechanics-based thermal Cracking model are presented. The funding provided by this NexTrans supplement allowed the development of the thermal Cracking software to include aspects which will facilitate its seamless integration into an overarching pavement management software program.
Emily J Rayfield - One of the best experts on this subject based on the ideXlab platform.
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testing the influence of crushing surface variation on seed Cracking Performance among beak morphs of the african seedcracker pyrenestes ostrinus
2021Co-Authors: Nicola S Heckeberg, Philip S L Anderson, Emily J RayfieldAbstract:Extreme phenotypic polymorphism is an oft-cited example of evolutionary theory in practise. Although these morphological variations are assumed to be adaptive, few studies have biomechanically tested such hypotheses. Pyrenestes ostrinus (the African seedcracker finch) shows an intraspecific polymorphism in beak size and shape that is entirely diet driven and allelically determined. Three distinct morphs feed upon soft sedge seeds during times of abundance, but switch to specializing on three different species of sedge seeds that differ significantly in hardness during lean times. Here we test the hypothesis that beak morphology is directly related to consuming seeds of different hardness. We used a novel experimental analysis to test how beak morphology affects the efficiency of Cracking sedge seeds of variable hardness. We found that neither mandibular ramus width nor crushing surface morphology had significant effects on the ability to crack different seed types. It is likely that feeding Performance is correlated with other aspects of beak size and shape such as beak depth and strength, muscle force, or gape. Our results highlight how even seemingly straightforward examples of adaptive selection in nature can be complex in practice.
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testing the influence of crushing surface variation on seed Cracking Performance between beak morphs of the african seedcracker pyrenestes ostrinus
2021Co-Authors: Nicola S Heckeberg, Philip S L Anderson, Emily J RayfieldAbstract:Extreme phenotypic polymorphism is an oft-cited example of evolutionary theory in practise. Although these morphological variations are assumed to be adaptive, few studies have biomechanically tested such hypotheses. Pyrenestes ostrinus (the African seedcracker finch) shows an intraspecific polymorphism in beak size and shape that is entirely diet driven and allelically determined. Three distinct morphs feed upon soft sedge seeds during times of abundance, but switch to specializing on three different species of sedge seeds that differ significantly in hardness during lean times. Here we test the hypothesis that beak morphology is directly related to consuming seeds of different hardness. We used a novel experimental analysis to test how beak morphology affects the efficiency of Cracking sedge seeds of variable hardness. We found that neither mandibular ramus width nor crushing surface morphology had significant effects on the ability to crack different seed types. It is likely that feeding Performance is correlated with other aspects of beak size and shape such as beak depth and strength, muscle force, or gape. Our results highlight how even seemingly straightforward examples of adaptive selection in nature can be complex in practice.
George Lopp - One of the best experts on this subject based on the ideXlab platform.
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evaluation of Cracking Performance for polymer modified asphalt mixtures with high rap content
2017Co-Authors: Reynaldo Roque, Cristian Cocconcelli, Michael Bekoe, George LoppAbstract:Fourteen reclaimed asphalt pavement (RAP) mixtures designed with different combinations of RAP sources, contents (up to 40%) and mixture conditioning levels were evaluated to determine the maximum allowable amount of RAP material in surface courses without jeopardising pavement Cracking Performance. Extracted RAP binder was blended with virgin polymer-modified asphalt (PMA) binder at various RAP binder replacement ratios. All blends behaved effectively as PMA binder as they met the multiple stress creep recovery (MSCR) %recovery requirement, and in addition they had satisfactory binder fracture energy density values. RAP gradation was found to significantly affect the fracture properties of RAP mixtures as it controls the distribution of RAP binder and potentially the degree of blending between virgin and RAP binder. Increased RAP content resulted in stronger (i.e. higher tensile strength) but more brittle (i.e. lower failure strain and lower mixture fracture energy) mixtures. However, after long-term ove...
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impact of hydrated lime on Cracking Performance of asphalt mixtures with oxidation and cyclic pore pressure
2016Co-Authors: Reynaldo Roque, George Lopp, Marco Isola, Michael BekoeAbstract:This research was conducted to evaluate the impact of hydrated lime (HL) on the Cracking Performance of asphalt mixtures for a broad range of aggregate types, including granites and limestones. A recently developed conditioning procedure, long-term oven aging (LTOA) plus cyclic pore pressure conditioning (CPPC), was employed to simulate the effects of long-term field aging on asphalt mixtures. The energy ratio (ER) approach, which took into account mixture properties that were known to be closely related to Cracking and was calibrated with cores taken from field-aged pavements throughout Florida, was used to evaluate the Cracking Performance of untreated and lime-treated mixtures. The results show that the introduction of HL appeared to mitigate the detrimental effects of oxidative aging and moisture (LTOA plus CPPC) on the damage and fracture-related properties of granite and limestone mixtures. This effect resulted in better Cracking Performance of these mixtures. Further analysis based on comparison of...
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development of a binder fracture test to determine fracture energy properties
2014Co-Authors: Tianying Niu, Reynaldo Roque, George LoppAbstract:Based on knowledge and findings that existing binder tests may not accurately predict Cracking Performance at intermediate temperatures, this study embarked in the development a new binder fracture energy test to fill this void. Nonlinear 3-D finite element analysis (FEA) was used to identify and optimise an appropriate specimen geometry to allow for accurate determination of true stress and strain on the fracture plane, thereby ensuring accurate determination of fracture energy. Various binders were tested at multiple temperatures and loading rates using prototype specimens in order to evaluate the feasibility and validity of different specimen geometries. The researchers used nonlinear FEA results to establish a data interpretation system and develop a set of diagrams to simplify calculation procedures. After extensive observation of test results, the researchers concluded that the new fracture energy test and data interpretation system suitably measure unmodified and modified binder fracture energy den...
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long term field evaluation and analysis of top down Cracking for superpave projects
2013Co-Authors: Jian Zou, Sanghyun Chun, Reynaldo Roque, George LoppAbstract:A field evaluation of Cracking Performance was undertaken for 10 pavement sections as part of a long-term Superpave monitoring project. It was found that top-down Cracking was the major type of Cracking. Also, moisture damage was identified in four of these sections. An analysis based on the energy ratio (ER) parameter showed that the mixtures that were affected by moisture generally exhibited a much faster reduction in the ER (indicating reduced fracture resistance) than those that were not. Further analysis of Cracking Performance was conducted using the enhanced hot mix asphalt fracture mechanics-based pavement Performance model (HMA-FM-E). The HMA-FM-E is capable of predicting the entire process of top-down Cracking from the onset of Cracking until pavement failure, and thus provides more valuable information that may better assist material and pavement engineers to optimise their designs. The results showed that the predictions for sections not affected by moisture generally agreed well with field ob...
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a mechanistic test to evaluate effects of interface condition characteristics on hot mix asphalt overlay reflective Cracking Performance
2013Co-Authors: Yu Chen, Gabriele Tebaldi, George Lopp, Reynaldo Roque, M ExlineAbstract:Reflective Cracking is a distress mode that is of particular concern for pavements with thin hot-mix asphalt (HMA) overlay as a maintenance and/or rehabilitation method. Traditionally, efforts have been made to mitigate reflective Cracking by increasing overlay thickness, using anti-reflective Cracking interlayer systems and special treatments on existing pavements and cracks. A new way to improve HMA overlay reflective Cracking resistance is to use highly polymer-modified asphalt emulsion (PMAE) interface. Tests currently available are not appropriate to evaluate the effects of interface conditions on reflective Cracking. This paper presents the second phase of a study devoted to develop a mechanistic test to study effects of interface conditions on pavement Cracking Performance. A new approach to represent reflective Cracking (a teflon spacer introduced in an existing pavement layer) instead of the traditional notch method was introduced to the composite specimen interface Cracking test developed for to...