Trb superpave Abstracts 2002

ABSTRACT

Recently, a field permeability device and test procedure have been developed and tested by the National Center for Asphalt Technology (NCAT) that has shown the ability to identify pavement areas with high permeability to water. This device works by measuring the amount of water that flows into a pavement over a given time period using a falling-head approach.

Based upon work conducted by NCAT, the use of this field permeability device has many potential benefits to the hot mix asphalt (HMA) industry. The field permeability device can be used as an almost real-time estimate of mat density and may be a good indicator of longitudinal joint quality. Because of the success NCAT has had with the device to date, a study was needed to evaluate the repeatability and reproducibility of the test method.

Results of the round-robin study indicated that an estimate of permeameter/operator reproducibility was 10.0x10^-5 cm/sec. An overall standard deviation on permeability measurements was found to be 24.4x10^-5 cm/sec. Additionally, criteria were developed based upon the variability of test results to specify field permeability testing for quality control type testing.
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Shear Properties as Viable Measures for Characterization of Permanent Deformation of Asphalt Concrete Mixtures

Stephen N Goodman, Program Manager, Canadian Strategic Highway Research Program (C-SHRP), 2323 St. Laurent Blvd., Ottawa, Ontario Canada, K1G 4J8, Tel: [phone], Fax: [phone], Email: [e-mail]
Yasser Hassan, Assistant Professor, Department of Civil and Environmental Engineering, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, Canada, K1S 5B6, Tel: [phone]X8625, Fax: [phone], E-mail: [e-mail].
Abd El Halim Omar Abd El Halim, Professor, Department of Civil and Environmental Engineering, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, Canada, K1S 5B6, Tel: [phone]X5789, Fax: [phone], E-mail: [e-mail].
Abstract.

Released in 1994, the Superpave asphalt mix design system represented the culmination of a US $50 million investment by the Strategic Highway Research Program (SHRP) to reduce the overall life cycle costs of asphalt pavements. At this time, an extensive investigation to recommend a laboratory based “simple performance test” for evaluating the resistance of Superpave mixes to permanent deformation is underway through the National Cooperative Highway Research Program. As a complementary effort, researchers at Carleton University are developing a field simple performance test for asphalt mixes known as the In-Situ Shear Stiffness Test (InSiSST™). Funded primarily by the Transportation Research Board and the Ontario Ministry of Transportation, InSiSST™ is unique to the asphalt industry as it measures the shear properties of compacted asphalt layers in the field without the need for coring or specimen preparation. Initial test results at the Superpave specific pavement studies test site (SPS-9) in Petawawa, Ontario have shown excellent correlation between the in-situ shear stiffness and observed permanent deformation. With additional testing and correlation, it is hoped that the InSiSST™ facility will complement the laboratory Superpave SPT to provide the asphalt industry with improved tools for mitigating permanent deformation. While the paper contains information concerning the development effort for context purposes, the main objective is to further establish the benefit of fundamental asphalt shear properties for characterizing resistance to permanent deformation by presenting new and powerful performance models relating asphalt mix properties and shear properties to permanent deformation.

Keywords: asphalt mixtures, Superpave, shear testing, shear stiffness, permanent deformation, Shell Method, torsion, performance models.
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The Effect of Various Aging Techniques on Asphalt Low-Temperature Properties

Daniel B. Knorr, Jr., Richard R. Davison, and Charles J. Glover*

Department Of Chemical Engineering and

The Texas Transportation Institute

Texas A&M University

College Station, Tx 77843-3122

[phone]

FAX [phone]

[e-mail]

ABSTRACT

This study includes three phases in which the effects of various aging techniques on asphalt low temperature properties were investigated. In Phase I it was shown that 38 days aging of a 1 mm thick asphalt film at 60°C and 1 atmosphere of air is approximately equivalent to 20 hours in the pressure aging vessel (PAV) of a 3.2 mm film at 100°C after both have been rolling thin-film oven test (RTFOT)-aged. Low-temperature properties of the samples were found not to vary significantly between the PAV and environmental room aged material. In Phase II of this work, a correlation was developed from the high-temperature parameter G*/sin(δ) at 58oC and 10 rad/s to correct the low-temperature performance grade when one desires to skip the long-term aging procedure. The correlation proved to give a maximum error of ±1.6°C for the low-temperature performance grade. In Phase III of this study it was shown that as asphalts are aged for extended periods their relative ranks with respect to Strategic Highway Research Program (SHRP) low temperature specifications may change. This indicates that the SHRP long-term aging specifications result in an arbitrary ranking of asphalts with respect to low-temperature properties.

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Aggregate Blending for Asphalt Mix Design: “The Bailey Method”

William R. Vavrik, Ph.D., P.E.

Senior Engineer

ERES Consultants Division

Applied Research Associates, Inc.

505 W. University Ave.

Champaign, Illinois 61820

[phone]

[phone] fax

[e-mail]
William J. Pine, P.E.

Research Engineer

Heritage Research

7901 W. Morris St.

Indianapolis, IN 46231

[phone]

[phone] fax

[e-mail]

Samuel H. Carpenter, Ph.D., P.E.

Professor

University of Illinois Urbana-Champaign

Department of Civil Engineering

205 N. Mathews Ave., MC-250

Urbana, Illinois 61801

[phone]

[phone] fax

[e-mail]

ABSTRACT

From the beginning of asphalt mixture design it was desired to understand the interaction of aggregates, asphalt , and the voids created during their compaction. In asphalt mixture design, guidance is lacking in the selection of the design aggregate structure and understanding the interaction of that aggregate structure and mixture volumetric properties.

This paper presents asphalt mixture design concepts that utilize aggregate interlock and aggregate packing to develop an aggregate blend that meets volumetric criteria and provides adequate compaction characteristics. The presented concepts rely on coarse aggregate for the skeleton of the mixture with the proper amount of fine aggregate to provide a properly packed aggregate structure. The objective is to utilize aggregate packing concepts to analyze the combined gradation and relate the packing characteristics to the mixture volumetric properties and compaction characteristics. The new concepts presented for asphalt mixture design and analysis include an examination of aggregate packing and aggregate interlock, blending aggregates by volume, a new understanding of coarse and fine aggregate, and an analysis of the resulting gradation. The concepts outlined in this paper are the result of many years of field experience and are the backbone of the Bailey Method for Asphalt Mix Design. These methods are under continued development as the improved method for asphalt mixture design, which will assist with the transition to contractor mix design.
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Effect of Crumb Rubber Particle Size and Content On The Low Temperature Rheological Properties of Binders

Venu T. Gopal1

Peter E. Sebaaly2

Jon Epps3
1. Graduate Research Assistant, Pavements/Materials Program, Department of Civil

Engineering, University of Nevada, Reno, Nevada, 89557. 775-784-1172, [e-mail]

2. Professor and Director, Pavements/Materials Program, Department of Civil Engineering,

University of Nevada, Reno, Nevada, 89557. 775-784-6565, [e-mail].

3. Materials Engineering Manager, Granite Construction Inc., Sparks, Nevada, 89432. 775-352-

1954, [e-mail]

ABSTRACT: This paper presents a study to evaluate low temperature rheological properties of crumb rubber modified binders and the impact of the particle size and content on such properties. Three sizes of the crumb rubber (0.18, 0.425 and 2.0 mm), a control (0%) and two levels of crumb rubber content (12% and 24%) were used with four asphalt binders. The measured rheological properties consisted of creep stiffness (St) and logarithmic creep rate (m). Results showed that: increasing the crumb rubber content decreased the creep stiffness which improves thermal cracking resistance. The impact of crumb rubber content on the m-value was very highly inconsistent. The crumb rubber size did not have significant effect on the low temperature properties. The effect of the size of the crumb rubber on the resistance to thermal cracking was dependent on the asphalt binder source. The analysis of the data generated in this experiment showed that some combinations of crumb rubber size and content can either improve or jeopardize the PG low temperature of the asphalt binder.
KEY WORDS: crumb rubber, Superpave, rheological properties, creep stiffness, logarithmic

creep rate, thermal cracking, low temperature properties.

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Precision Statements For The Ignition Oven Using Plant-Produced Mix

Gregory A. Sholar

352.337.3278

[e-mail]
Gale C. Page

352.337.3208

[e-mail]
James A. Musselman

352.337.3150

[e-mail]