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L. Allen Cooley - One of the best experts on this subject based on the ideXlab platform.
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INVESTIGATION OF THE TENDER ZONE IN THE COMPACTION OF COARSE-GRADED SUPERPAVE HOT MIX ASPHALT (HMA) MIXES
2003Co-Authors: M. Shane Buchanan, L. Allen CooleyAbstract:Tender hot mix asphalt (HMA) mixes have been observed and experienced by paving contractors for many years. However, during the field compaction of coarse-graded Superpave mixes, a “tender zone”, not a true tender mix, is sometimes experienced. The tender zone is range of mix compaction temperatures during which the mix exhibits instability during roller action. There have been many possible causes of the tender zone presented including differences in lab and production absorption, mix moisture, low dust to asphalt ratio, increased asphalt Binder Film thickness, and a temperature differential with the lift. A study was conducted to document and evaluate field mixes exhibiting the tender zone to determine the possible cause(s) for its occurrence. Documentation included mix, production, and construction related items. Laboratory evaluation consisted of mix gradation and volumetric testing along with Superpave asphalt Binder testing on the project asphalt Binder before and after steam distillation. Project results failed to clearly identify one particular reason for the tender zone occurrence. However, it is felt that the tender zone was a result of field absorption being less than design and increased asphalt Binder Film thickness acting in conjunction with an inherent temperature differential within the lift.
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INVESTIGATION OF TENDER ZONE IN COMPACTION OF COARSE-GRADED SUPERPAVE (REGISTERED TRADEMARK) HOT-MIX ASPHALT MIXTURES
Transportation Research Record, 2003Co-Authors: M. Shane Buchanan, L. Allen CooleyAbstract:Tender hot-mix asphalt mixtures have been observed and experienced by paving contractors for many years. However, during the field compaction of coarse-graded Superpave (registered trademark) mixes, a tender zone, not a true tender mix, is sometimes experienced. The tender zone is a range of mix compaction temperatures during which the mixture exhibits instability during roller action. Many possible causes of the tender zone have been presented, including differences in laboratory and production absorption, mix moisture, a low dust-to-asphalt ratio, increased asphalt Binder Film thickness, and a temperature differential with the lift. A study was conducted to document and evaluate field mixtures exhibiting the tender zone to determine the possible cause(s) of its occurrence. Documentation included mix-, production-, and construction-related items. Laboratory evaluation consisted of mixture gradation and volumetric testing along with Superpave asphalt Binder testing with the project asphalt Binder before and after steam distillation. Project results failed to clearly identify one particular reason for the occurrence of the tender zone. However, it is believed that the tender zone was a result of field absorption being less than the design absorption and increased asphalt Binder Film thickness acting in conjunction with an inherent temperature differential within the lift.
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Investigation of Tender Zone in Compaction of Coarse-Graded Superpave® Hot-Mix Asphalt Mixtures
Transportation Research Record: Journal of the Transportation Research Board, 2003Co-Authors: M. Shane Buchanan, L. Allen CooleyAbstract:Tender hot-mix asphalt mixtures have been observed and experienced by paving contractors for many years. However, during the field compaction of coarse-graded Superpave® mixes, a "tender zone," not a true tender mix, is sometimes experienced. The tender zone is a range of mix compaction temperatures during which the mixture exhibits instability during roller action. Many possible causes of the tender zone have been presented, including differences in laboratory and production absorption, mix moisture, a low dust-to-asphalt ratio, increased asphalt Binder Film thickness, and a temperature differential with the lift. A study was conducted to document and evaluate field mixtures exhibiting the tender zone to determine the possible cause(s) of its occurrence. Documentation included mix-, production-, and construction-related items. Laboratory evaluation consisted of mixture gradation and volumetric testing along with Superpave asphalt Binder testing with the project asphalt Binder before and after steam distillation. Project results failed to clearly identify one particular reason for the occurrence of the tender zone. However, it is believed that the tender zone was a result of field absorption being less than the design absorption and increased asphalt Binder Film thickness acting in conjunction with an inherent temperature differential within the lift.
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Investigation of tender zone in compaction of coarse-graded Superpave hot-mix asphalt mixtures
Transportation Research Record, 2003Co-Authors: M. Shane Buchanan, L. Allen CooleyAbstract:Tender hot-mix asphalt mixtures have been observed and experienced by paving contractors for many years. However, during the field compaction of coarse-graded Superpave® mixes, a "tender zone," not a true tender mix, is sometimes experienced. The tender zone is a range of mix compaction temperatures during which the mixture exhibits instability during roller action. Many possible causes of the tender zone have been presented, including differences in laboratory and production absorption, mix moisture, a low dust-to-asphalt ratio, increased asphalt Binder Film thickness, and a temperature differential with the lift. A study was conducted to document and evaluate field mixtures exhibiting the tender zone to determine the possible cause(s) of its occurrence. Documentation included mix-, production-, and construction-related items. Laboratory evaluation consisted of mixture gradation and volumetric testing along with Superpave asphalt Binder testing with the project asphalt Binder before and after steam disti...
M. Shane Buchanan - One of the best experts on this subject based on the ideXlab platform.
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INVESTIGATION OF THE TENDER ZONE IN THE COMPACTION OF COARSE-GRADED SUPERPAVE HOT MIX ASPHALT (HMA) MIXES
2003Co-Authors: M. Shane Buchanan, L. Allen CooleyAbstract:Tender hot mix asphalt (HMA) mixes have been observed and experienced by paving contractors for many years. However, during the field compaction of coarse-graded Superpave mixes, a “tender zone”, not a true tender mix, is sometimes experienced. The tender zone is range of mix compaction temperatures during which the mix exhibits instability during roller action. There have been many possible causes of the tender zone presented including differences in lab and production absorption, mix moisture, low dust to asphalt ratio, increased asphalt Binder Film thickness, and a temperature differential with the lift. A study was conducted to document and evaluate field mixes exhibiting the tender zone to determine the possible cause(s) for its occurrence. Documentation included mix, production, and construction related items. Laboratory evaluation consisted of mix gradation and volumetric testing along with Superpave asphalt Binder testing on the project asphalt Binder before and after steam distillation. Project results failed to clearly identify one particular reason for the tender zone occurrence. However, it is felt that the tender zone was a result of field absorption being less than design and increased asphalt Binder Film thickness acting in conjunction with an inherent temperature differential within the lift.
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INVESTIGATION OF TENDER ZONE IN COMPACTION OF COARSE-GRADED SUPERPAVE (REGISTERED TRADEMARK) HOT-MIX ASPHALT MIXTURES
Transportation Research Record, 2003Co-Authors: M. Shane Buchanan, L. Allen CooleyAbstract:Tender hot-mix asphalt mixtures have been observed and experienced by paving contractors for many years. However, during the field compaction of coarse-graded Superpave (registered trademark) mixes, a tender zone, not a true tender mix, is sometimes experienced. The tender zone is a range of mix compaction temperatures during which the mixture exhibits instability during roller action. Many possible causes of the tender zone have been presented, including differences in laboratory and production absorption, mix moisture, a low dust-to-asphalt ratio, increased asphalt Binder Film thickness, and a temperature differential with the lift. A study was conducted to document and evaluate field mixtures exhibiting the tender zone to determine the possible cause(s) of its occurrence. Documentation included mix-, production-, and construction-related items. Laboratory evaluation consisted of mixture gradation and volumetric testing along with Superpave asphalt Binder testing with the project asphalt Binder before and after steam distillation. Project results failed to clearly identify one particular reason for the occurrence of the tender zone. However, it is believed that the tender zone was a result of field absorption being less than the design absorption and increased asphalt Binder Film thickness acting in conjunction with an inherent temperature differential within the lift.
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Investigation of Tender Zone in Compaction of Coarse-Graded Superpave® Hot-Mix Asphalt Mixtures
Transportation Research Record: Journal of the Transportation Research Board, 2003Co-Authors: M. Shane Buchanan, L. Allen CooleyAbstract:Tender hot-mix asphalt mixtures have been observed and experienced by paving contractors for many years. However, during the field compaction of coarse-graded Superpave® mixes, a "tender zone," not a true tender mix, is sometimes experienced. The tender zone is a range of mix compaction temperatures during which the mixture exhibits instability during roller action. Many possible causes of the tender zone have been presented, including differences in laboratory and production absorption, mix moisture, a low dust-to-asphalt ratio, increased asphalt Binder Film thickness, and a temperature differential with the lift. A study was conducted to document and evaluate field mixtures exhibiting the tender zone to determine the possible cause(s) of its occurrence. Documentation included mix-, production-, and construction-related items. Laboratory evaluation consisted of mixture gradation and volumetric testing along with Superpave asphalt Binder testing with the project asphalt Binder before and after steam distillation. Project results failed to clearly identify one particular reason for the occurrence of the tender zone. However, it is believed that the tender zone was a result of field absorption being less than the design absorption and increased asphalt Binder Film thickness acting in conjunction with an inherent temperature differential within the lift.
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Investigation of tender zone in compaction of coarse-graded Superpave hot-mix asphalt mixtures
Transportation Research Record, 2003Co-Authors: M. Shane Buchanan, L. Allen CooleyAbstract:Tender hot-mix asphalt mixtures have been observed and experienced by paving contractors for many years. However, during the field compaction of coarse-graded Superpave® mixes, a "tender zone," not a true tender mix, is sometimes experienced. The tender zone is a range of mix compaction temperatures during which the mixture exhibits instability during roller action. Many possible causes of the tender zone have been presented, including differences in laboratory and production absorption, mix moisture, a low dust-to-asphalt ratio, increased asphalt Binder Film thickness, and a temperature differential with the lift. A study was conducted to document and evaluate field mixtures exhibiting the tender zone to determine the possible cause(s) of its occurrence. Documentation included mix-, production-, and construction-related items. Laboratory evaluation consisted of mixture gradation and volumetric testing along with Superpave asphalt Binder testing with the project asphalt Binder before and after steam disti...
Egons Tons - One of the best experts on this subject based on the ideXlab platform.
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aggregate rugosity and size effect on bituminous mixes
Transportation Research Record, 1998Co-Authors: Taisir S. Khedaywi, Egons TonsAbstract:Higher costs and possible restricted availability of asphalt have stimulated research and discussion on how to reduce the amount of asphalt in bituminous mixes without sacrificing service. A hypothesis was proposed suggesting that for each coarse aggregate type with different surface characteristics there is a specific fine aggregate size that contributes to developing an interlocking mechanism between the surfaces of coarse aggregates when they are combined in a bituminous mix. To test this hypothesis, two types of coarse aggregates having different surface characteristics or rugosity, limestone and rounded gravel, were used. For each aggregate, two one-size fractions were tested—19 mm to 25 mm and 6.4 mm to 4.75 mm. One type of fine aggregate (limestone) with five one-size fractions was used. Four flow Binder Film thicknesses were chosen. The packing volume and rugosity concepts were the theoretical basis. Asphalt and aggregate mixes were tested in compression. The results were evaluated by the use of r...
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Aggregate Rugosity and Size Effect on Bituminous Mixes
Transportation Research Record: Journal of the Transportation Research Board, 1998Co-Authors: Taisir S. Khedaywi, Egons TonsAbstract:Higher costs and possible restricted availability of asphalt have stimulated research and discussion on how to reduce the amount of asphalt in bituminous mixes without sacrificing service. A hypothesis was proposed suggesting that for each coarse aggregate type with different surface characteristics there is a specific fine aggregate size that contributes to developing an interlocking mechanism between the surfaces of coarse aggregates when they are combined in a bituminous mix. To test this hypothesis, two types of coarse aggregates having different surface characteristics or rugosity, limestone and rounded gravel, were used. For each aggregate, two one-size fractions were tested—19 mm to 25 mm and 6.4 mm to 4.75 mm. One type of fine aggregate (limestone) with five one-size fractions was used. Four flow Binder Film thicknesses were chosen. The packing volume and rugosity concepts were the theoretical basis. Asphalt and aggregate mixes were tested in compression. The results were evaluated by the use of regression equations. Graphical presentations and illustrations were used as necessary. Unconfined compression test results showed that for one-size limestone coarse aggregate, the highest strength values were associated with No. 60 to No. 80 fines in the mix and for one-size rounded gravel coarse aggregate, the highest strength occurred when No. 200 to No. 270 fines were added to the mix. The highest strength was associated with 50 μm flow Binder Film thickness for all mixes.
Samuel H Carpenter - One of the best experts on this subject based on the ideXlab platform.
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validity of asphalt Binder Film thickness concept in hot mix asphalt
Transportation Research Record, 2008Co-Authors: Mostafa A Elseifi, Shih Hsien Yang, Imad L Alqadi, Samuel H CarpenterAbstract:Despite the possible benefits of implementing asphalt Binder Film thickness into current specifications to address durability problems, most of the related research has been theoretical and only a few attempts have been made to measure this property experimentally. The objective of this study was to investigate the concept of asphalt Binder Film thickness experimentally on the basis of measurements obtained by image analysis techniques, reflective light microscopy, and scanning electron microscopy. The results of the experimental program were used to gain insight into the concept of asphalt Binder Film thickness and its validity. Experimental results indicated that asphalt Binder Films coating large aggregates do not actually exist in hot-mix asphalt. Instead, what are referred to as asphalt Binder Films surrounding large aggregates are actually asphalt mastic Films. These Films are highly irregular in shape and have a thickness greater than 100 μm in the mixture considered in this study. The asphalt bind...
Lily D. Poulikakos - One of the best experts on this subject based on the ideXlab platform.
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measuring the Binder Film residues on black rock in mixtures with high amounts of reclaimed asphalt
Journal of Cleaner Production, 2017Co-Authors: Maria Chiara Cavalli, Manfred N. Partl, Lily D. PoulikakosAbstract:Reclaimed asphalt pavement (RAP) and virgin materials were mixed and analysed using electron microscopy and image analysis techniques. Titanium dioxide was added as a tracer in the virgin bitumen to detect the effect of mixing temperature on the “RAP Binder Film thickness” which is the stiffer Binder in the mixture in comparison to the virgin Binder. The analysis conducted with the environmental scanning electron microscopy and X-Ray spectroscopy has shown that the RAP Binder, instead of completely blending with the new Binder, forms a layered structure coating the RAP aggregates. This structure is composed of an inner layer of RAP Binder that is not blended with the virgin bitumen indicating the existence of the “black rock”. The RAP Binder Film thickness is a function of mixing temperature, local aggregate curvature and size of aggregates. The higher the mixing temperature, the thinner the layer of RAP Binder tends to be. RAP Binder Film thickness was measured at micro-scale and subsequently statistically analysed showing that along the surface of the aggregate it is not homogenous; it depends on the local curvature of the aggregate, with positive curvature resulting in a smaller Film thickness and negative curvature in larger Film thickness.
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Multiscale imaging and characterization of the effect of mixing temperature on asphalt concrete containing recycled components.
Journal of microscopy, 2016Co-Authors: Maria Chiara Cavalli, Michele Griffa, Sara Bressi, Manfred N. Partl, Gabriele Tebaldi, Lily D. PoulikakosAbstract:When producing asphalt concrete mixture with high amounts of reclaimed asphalt pavement (RAP), the mixing temperature plays a significant role in the resulting spatial distribution of the components as well as on the quality of the resulting mixture, in terms of workability during mixing and compaction as well as in service mechanical properties. Asphalt concrete containing 50% RAP was investigated at mixing temperatures of 140, 160 and 180°C, using a multiscale approach. At the microscale, using energy dispersive X-ray spectroscopy the RAP Binder Film thickness was visualized and measured. It was shown that at higher mixing temperatures this Film thickness was reduced. The reduction in Film thickness can be attributed to the loss of volatiles as well as the mixing of RAP Binder with virgin Binder at higher temperatures. X-ray computer tomography was used to characterize statistically the distribution of the RAP and virgin aggregates geometric features: volume, width and shape anisotropy. In addition using X-ray computer tomography, the packing and spatial distribution of the RAP and virgin aggregates was characterized using the nearest neighbour metric. It was shown that mixing temperature may have a positive effect on the spatial distribution of the aggregates but did not affect the packing. The study shows a tendency for the RAP aggregates to be more likely distributed in clusters at lower mixing temperatures. At higher temperatures, they were more homogeneously distributed. This indicates a higher degree of blending both at microscale (Binder Film) and macroscale (spatial distribution) between RAP and virgin aggregates as a result of increasing mixing temperatures and the ability to quantify this using various imaging techniques.