Trb superpave Abstracts 2002

Florida Department Of Transportation

2006 NE Waldo Road

Gainesville, FL 32609

Fax: [phone]

ABSTRACT

The current precision values given in Florida Method FM 5-563 for the determination of asphalt binder content by use of the ignition oven are based on laboratory fabricated specimens with known binder contents and gradations (1). This study was conducted to determine precision values for both asphalt binder content and gradation using plant produced mix. This approach would encompass the variability associated with: 1) differences in an asphalt mixture within the truck bed, 2) sampling the truck, 3) splitting the mix into sample size, 4) differences in ignition oven equipment, and 5) variability associated with the operator. The current precision values only include the variability associated with items four and five and the variability associated with batching and mixing laboratory prepared specimens. Twelve laboratories tested nine different mixtures containing a wide variety of gradations and aggregate types. The results of the study indicate that the allowable difference between two test results for asphalt binder content should be no greater than 0.32% within-lab and 0.44% between-labs. New graphs were developed for the within-lab and between-lab precision values for aggregate gradation. Separate graphs were developed for dense graded Superpave mixtures and open-graded friction course mixtures since it was determined that allowable tolerances differ significantly for each type of mixture.

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Dynamic Modulus of Asphalt Concrete Using a Hollow Cylinder Tensile Tester

William G. Buttlar, Ph.D., P.E.

Assistant Professor, Department of Civil and Environmental Engineering

University of Illinois at Urbana-Champaign

205 North Mathews Avenue

1212 Newmark Civil Engineering Laboratory

Urbana, Illinois 61801

Jason M. Bauer

Research Assistant, Department of Civil and Environmental Engineering

University of Illinois at Urbana-Champaign

205 North Mathews Avenue

3214 Newmark Civil Engineering Laboratory

Urbana, Illinois 61801

Daniel S. Sherman, Research Assistant

Department of Civil and Environmental Engineering

University of Illinois at Urbana-Champaign

205 North Mathews Avenue

3214 Newmark Civil Engineering Laboratory

Urbana, Illinois 61801

ABSTRACT

A hollow cylinder tensile tester (HCT) has recently been shown to be a suitable surrogate test device for the Superpave Indirect Tension Test. In this study, the feasibility of using the HCT to obtain the dynamic modulus of asphalt concrete was explored. Previous studies have shown the dynamic modulus of asphalt concrete in tension and compression to be similar at low temperatures and/ or high loading frequencies, and that minor differences can be expected at higher temperatures or lower loading frequencies. In this study, the HCT device was shown to compare favorably with dynamic modulus measurements obtained with uniaxial compression testing apparatus at 0 and 20 degrees Celsius. In addition, test results were shown to be in reasonable agreement with the Witczak dynamic modulus predictive equation. The ability to simply and rapidly measure the creep compliance, tensile strength, and dynamic modulus of bituminous paving mixtures over a range of temperatures and loading conditions make the HCT device a useful general-purpose mixture analysis tool. It appears that this portable device may serve as a practical method to satisfy testing requirements for high reliability (level 1) pavement designs in the forthcoming AASHTO design guide being developed under NCHRP 1-37A for the mitigation of both fatigue cracking and thermal cracking. However, a broader experimental program, including tests at higher temperatures and a broader range of test frequencies, will be needed to fully validate the compatibility of HCT measurements with NCHRP 1-37A models.

KEYWORDS: Dynamic Modulus, E*, Stiffness, Hollow Cylinder, Asphalt, Asphalt Concrete,

Asphalt Mixtures, HMA

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Use of Stiffness of Hot-Mix Asphalt as a Simple Performance Test

Terhi K. Pellinen

School of Civil Engineering, Purdue University, 1284 Civil Engineering Building

West Lafayette, IN 47907-1284
Matthew W. Witczak, College of Engineering and Applied Science, Civil and Environmental Engineering

Arizona State University, PO Box 875306, Tempe, AZ 85287-5306

The objective of this study was to investigate if the stiffness of a mix could be used as a Simple Performance Test (SPT) parameter to complement the Superpave volumetric mix design. This was completed through a statistical analysis of the strength of correlation between different mixture stiffness parameters and field performance (rutting, thermal and fatigue cracking). A total of 30 mixtures were tested using laboratory-fabricated specimens. The studied stiffness parameters were compressive dynamic (complex) modulus |E*|, Simple Shear Tester (SST) shear (complex) modulus |G*|, and dynamic elastic modulus Ed obtained from ultrasonic wave propagation. Also, computed stiffness factors |E*|/sin  and |G*|/sin for rutting and |E*|sin for cracking were studied as analogous to the Superpave binder specification. Research indicated that the correlation to rutting varied based on test temperature and frequency, and it peaked at 54.4°C test temperature and 5 Hz. At peak conditions, the |E*|/sin had better statistical correlation to rutting than |E*|, but correlations reversed at lower frequencies. Although the |E*| and |G*| had similar correlation to rutting, analysis of test data indicated that the SST-shear testing gave lower stiffness values and higher phase angle values than the compressive dynamic modulus testing, even when considering Poisson’s ratio effects. This was especially true at high temperatures. Because of these and other reasons, the dynamic modulus |E*| was recommended as the SPT parameter for rutting, as well as for fatigue cracking. None of the studied parameters turn out to be good enough performance indicators for thermal cracking.

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A Simple Performance Test for Fatigue Cracking of Asphalt Concrete Based on Viscoelastic Analysis of Indirect Tensile Testing and its Validation Using Westrack Asphalt Mixtures

Haifang Wen, Graduate Research Assistant

Y. Richard Kim, Professor

Department of Civil Engineering

North Carolina State University

P.O. Box 7908

Raleigh, NC 27695

Tel: [phone]

Fax: [phone]

Email: [e-mail]

ABSTRACT

This paper presents the viscoelastic characterization of asphalt concrete in indirect tensile testing (IDT) and the development of a simple performance test for fatigue cracking. A 50 mm gauge length was adopted to measure the horizontal and vertical deformations using surface mounted LVDTs on an IDT specimen with a 100/150 mm diameter and 38 mm thickness. The effect of a concentrated load under loading strips on vertical displacement within the 50 mm gauge length was evaluated using the Digital Image Correlation method, a noncontact, full-field displacement/strain measurement technique. The theory of viscoelasticity was used to develop analytical solutions for creep compliance and center strain from displacements measured on the specimen surface. These solutions were verified by 3-D finite element viscoelastic analysis. Indirect tensile creep and strength tests were performed on fine and coarse mixtures from WesTrack with varying asphalt contents and air void contents, and various parameters determined from the analysis of these data were compared against the known fatigue performance of these mixtures from the WesTrack testing facility. Fracture energy obtained from the viscoelastic analysis of the indirect tensile strength test at 20C correlated highly with the field performance of these mixtures at WesTrack.

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Determination of Moisture in HMA and Relationship with Tender Mix Behavior in the Laboratory

Gerald A. Huber

Heritage Research Group

7901 West Morris Street

Indianapolis, IN 46231

317.390.3141 (voice)

317.486.2985 (FAX)

[e-mail]

James A. Scherocman

Consultant

11205 Brookbridge Dr.

Cincinnati, OH 45249

513.489.3338 (voice)

513.489.3349 (FAX)

[e-mail]
John D’Angelo

Federal Highway Administration

400 Seventh Street SW, Room 3118

Washington, DC 20590

202.366.0121 (voice)

202.493.2070 (FAX)

John.D’[e-mail]
Robert L. Peterson

Asphalt Institute

P.O. Box 14052

Lexington, KY 40512-4052

859.288.4977 (voice)

859.288.4999 (FAX)

[e-mail]
R. Michael Anderson* Corresponding Author

Asphalt Institute

859.288.4984 (voice)

859.288.4999 (FAX)

[e-mail]
Mark S. Buncher

Asphalt Institute

859.288.4972 (voice)

859.288.4999 (FAX)

[e-mail]