Investigation of Low Temperature Cracking in Asphalt Pavements: National Pooled Fund Executive Summary

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Date Created
2007-05
Description
Good fracture properties are an essential requirement for asphalt pavements built in the northern part of the US and in Canada for which the predominant failure mode is cracking due to high thermal stresses that develop at low temperatures. Currently, there is no agreement with respect to what experimental methods and analyses approaches to use to investigate the fracture resistance of asphalt materials and the fracture performance of asphalt pavements. This report presents a comprehensive research effort in which both traditional and new experimental protocols and analyses were applied to a statistically designed set of laboratory prepared specimens and to field samples from pavements with well documented performance to determine the best combination of experimental work and analyses to improve the low temperature fracture resistance of asphalt pavements. The two sets of materials were evaluated using current testing protocols, such as creep and strength for asphalt binders and mixtures as well as newly developed testing protocols, such as the disk compact tension test, single edge notched beam test, and semi circular bend test. Dilatometric measurements were performed on both asphalt binders and mixtures to determine the coefficient of thermal contraction. Discrete fracture and damage tools were utilized to model crack initiation and propagation in pavement systems using the finite element method and TCMODEL was used with the experimental data from the field samples to predict performance and compare it to the field performance data.

Incorporation of Recycled Asphalt Shingles in Hot-Mixed Asphalt Pavement Mixtures

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Date Created
2010
Report Number
2010-08
Description
Rises in construction and asphalt binder costs, as well as the growing pressures on landfills, have contributed to the increased use of tear-off scrap shingles (TOSS) and manufacturer waste scrap shingles (MWSS) into hot-mixed asphalt (HMA) pavement mixtures. This research project was undertaken to address the responsible incorporation of recycled asphalt shingles (RAS) into HMA pavement mixtures to ensure environmental benefits are realized and pavement durability is retained or improved. The research consisted of a literature review, extensive laboratory testing and field evaluations of in service RAS/RAP HMA pavements. Binder testing established a strong correlation between the new asphalt binder to total asphalt binder ratio and the extracted high/low binder performance grade temperatures. Dynamic modulus testing on HMA mixtures proved to be an invaluable tool in comparing the effects of RAS and RAP on mixture properties across a wide range of temperatures. Field performance appeared to validate the laboratory findings in some instances.

Recommended Practices for Crack Sealing HMA Pavement

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Date Created
2008
Report Number
2008-54
Description
This report is intended to present the conclusions from LRRB 822 Tasks 1-3 in combination with several other pertinent sources including: Chapter 4 of the Best Practices Handbook on Asphalt Pavement Maintenance (2000-04), the Guidelines for Sealing and Filling Cracks in Asphalt Concrete Pavement - Best Practice by the National Guide to Sustainable Municipal Infrastructure (NRC-CNRC, 2003), and Special Provision 2331, Bituminous Pavement Crack Treatment (Mn/DOT-Revised 2/7/2008).

Investigation of Low Temperature Cracking in Asphalt Pavements

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Date Created
2007
Report Number
2007-43
Description
Good fracture properties are an essential requirement for asphalt pavements built in the northern part of the US and in Canada for which the predominant failure mode is cracking due to high thermal stresses that develop at low temperatures. Currently, there is no agreement with respect to what experimental methods and analyses approaches to use to investigate the fracture resistance of asphalt materials and the fracture performance of asphalt pavements. This report presents a comprehensive research effort in which both traditional and new experimental protocols and analyses were applied to a statistically designed set of laboratory prepared specimens and to field samples from pavements with well documented performance to determine the best combination of experimental work and analyses to improve the low temperature fracture resistance of asphalt pavements. The two sets of materials were evaluated using current testing protocols, such as creep and strength for asphalt binders and mixtures as well as newly developed testing protocols, such as the disk compact tension test, single edge notched beam test, and semi circular bend test. Dilatometric measurements were performed on both asphalt binders and mixtures to determine the coefficient of thermal contraction. Discrete fracture and damage tools were utilized to model crack initiation and propagation in pavement systems using the finite element method and TCMODEL was used with the experimental data from the field samples to predict performance and compare it to the field performance data.

Selection of An Alternative Asphalt Extraction Solvent

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Date Created
2001
Report Number
2003-35
Description
The asphalt extraction solvent n-Propyl Bromide (nPB) was selected as an alternative solvent to the currently used d-Limonene and Trichloroethylene (TCE), based on a literature search, communication with asphalt technology experts, and a laboratory investigation. With proper handling techniques and training, nPB can be substituted for d-Limonene and TCE. Extractions with nPB use less solvent per extraction, take less time, and have a shorter drying times. Exposure levels to nPB for the labs were far below the EPA recommended value. The use of nPB for asphalt extraction and the implementation of nPB on-site recycling would generate only non-hazardous still bottom waste. The use of nPB would decrease the hazardous waste of laboratories and reduce annual solvent costs. Payback time for the purchase of solvent recovery units ranges from 3 months to 20 years, depending on the quantities of extraction waste generated per year. It is recommended that all Mn/DOT district laboratories change from d-Limonene or TCE extraction solvents to nPB and conduct on-site recycling with the purchase of solvent recovery systems, and that training be given to lab personnel on the proper handling techniques for nPB.