Trb superpave Abstracts 2002

ABSTRACT

A pavement design concept called “perpetual pavement” is being pursued by the hot mix asphalt industry in the United States. This concept proposes a pavement structure consisting of a rut resistant, impermeable, and wear resistant top structural layer, with a rut resistant and durable intermediate layer over a fatigue and durable base layer. The goal being a long life pavement needing only infrequent surface replacement. The paper’s intent is to provide the concepts and thought process used by Illinois and its hot mix industry to develop contract provisions for Extended Life HMA Pavements. This paper describes (1) the approach taken and (2) the issues involved and how they were addressed.
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2-D Image-Based Volumetric Modeling for Crushed Limestone Aggregates

Larry Banta, Department of Mechanical and Aerospace Engineering, West Virginia University,

PO Box 6106, Morgantown, WV 26506-6106

Telephone: [phone] ext 2334 FAX: [phone] email: [e-mail]
Ken Cheng, Rapiscan Security Products, Inc., 3232 W. El Segundo Blvd., Hawthorne, CA 90250

Telephone: [phone] FAX: [phone] email: [e-mail]

John Zaniewski, Harley O. Staggers National Transportation Center,

Department of Civil and Environmental Engineering, West Virginia University

PO Box 6103, Morgantown, WV 26506-6103

Telephone: [phone] ext 2648 FAX [phone] email: [e-mail]

ABSTRACT

In pavement construction, it is necessary to know the mass of stone aggregate particles for gradation analysis. In this paper, an approach for predicting particle mass based on 2-D electronic images is explored. Crushed limestone aggregates, similar to those used in asphalt pavement mixtures were placed on a light table and imaged using a CCD video camera and framegrabber. The images were processed to separate touching and overlapping particles, define the edges of the particles and to calculate certain features of the particle silhouettes, such as area, centroid and shape-related features. Several dimensionless parameters were defined, based on the image features. A multiple linear regression model was created, using the dimensionless parameters as regressor variables to predict particle mass. Regressor coefficients were found by fitting to a sample of 501 particles ranging in size from 4.75mm < particle sieve size <25 mm. When tested against a different aggregate sample, the model predicted the mass of the batch to within ±2%.

Key Words: limestone aggregates, sieving, image processing, shape analysis
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Application of the Digital Image Correlation Method to Mechanical Testing of Asphalt-Aggregate Mixtures

Youngguk Seo, Graduate Research Assistant, and Y. Richard Kim, Professor

Department of Civil Engineering

North Carolina State University

Raleigh, NC

E-mail: [e-mail], E-mail: [e-mail]

Ph: 919-515-7758

Fax: [phone]
Matthew W. Witczak, Professor, Department of Civil and Environmental Sciences

Arizona State University

Ramon Bonaquist

Advanced Asphalt Technologies

ABSTRACT

The digital image correlation (DIC) method, a non-contact, full-field displacement measurement technique, has been applied to mechanical testing of asphalt concrete. A single CCD (Couple Charged Device) camera acquires images of an area of interest from a specimen in the undeformed and deformed states. These images are correlated to determine deformations, and advanced mathematical procedures are applied to these deformations to calculate strains. To verify the DIC measurements, vertical displacements for the middle and bottom sections of a specimen subjected to monotonic tension are compared with conventional LVDT measurements. A series of DIC images captured during the monotonic and cyclic tests visualizes the evolution of the failure zone (i.e., the fracture process zone) at the crack tip. Also, it is demonstrated that the full-field measurement and post-processing nature of DIC allows a more accurate determination of the stress-strain behavior of the fracture process zone. Applicability of this method to a cylindrical specimen with a curved surface is also investigated by testing a 75 mm diameter cylindrical specimen. Finally, the DIC method is extended to cyclic testing of asphalt mixtures with the aid of a synchronized image acquisition technique.

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Determining the Low-Temperature Fracture Toughness of Asphalt Mixtures

Dr. Mihai O. Marasteanu

Assistant Professor, University of Minnesota

500 Pillsbury Drive S.E., Minneapolis, MN 55455

Telephone: [phone], E-mail: [e-mail]

Dr. Joseph F. Labuz

Associate Professor, University of Minnesota

500 Pillsbury Drive S.E., Minneapolis, MN 55455

Telephone: [phone], E-mail: [e-mail]

Dr. Shongtao Dai

Research Operations Engineer, Office of Materials and Road Research

Minnesota Department of Transportation, Maplewood, MN 55109

Tel: [phone], E-mail: [e-mail]

Xue Li

Graduate student, University of Minnesota

500 Pillsbury Drive S.E., Minneapolis, MN 55455

Telephone: [phone], E-mail: [e-mail]

ABSTRACT

There has been a sustained effort in applying fracture mechanics concepts to crack formation and propagation in bituminous pavement materials. Adequate fracture resistance is an essential requirement for asphalt pavements built in the northern part of the US and Canada for which the prevailing failure mode is cracking due to low-temperature shrinkage stresses. The current Superpave specifications address this issue mainly through the use of strength tests on unnotched (smooth boundary) specimens. However, recent studies have shown the limitations of this approach and have suggested that fracture mechanics concepts, based on tests performed on notched samples, should be employed instead.

Research in progress at University of Minnesota investigates the use of fracture mechanics principles to determine the low-temperature fracture properties of asphalt mixtures. This paper presents a testing protocol that allows obtaining multiple measurements of fracture toughness as a function of crack propagation based on the compliance method to measure crack length. An increase in fracture toughness with crack length is observed, which is consistent with the behavior displayed by other brittle materials. The plateau of the curves may be representative of the asphalt concrete resistance to fracture because the initial values can be significantly influenced by the presence of the inelastic zone at the crack tip.

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Effect of Wearing Surface Characteristics on Measured Pavement Skid Resistance and Texture

Robin M. Davis,

Graduate Research Assistant, Virginia Tech Transportation Institute, 3500 Transportation Research Drive, Blacksburg, VA 24061-0105, voice [phone], fax [phone], email: [e-mail].

Gerardo W. Flintsch

Assistant Professor , The Via Department of Civil and Environmental Engineering, 200 Patton Hall, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0105 voice [phone], fax [phone], email: [e-mail].

Imad L. Al-Qadi

Professor and Roadway Infrastructure Group Leader,

Virginia Tech Transportation Institute, 3500 Transportation Research Drive, Blacksburg, VA 24061-0105, voice [phone], fax [phone], email: [e-mail].
Kevin K. McGhee

Senior Research Scientist, Virginia Transportation Research Council, 530 Edgemont Road

Charlottesville, VA 22903, voice [phone], fax [phone], [e-mail]
Abstract

Variation in skid resistance and surface macrotexture measurements due to testing conditions such as tire, test vehicle speed, pavement grade, and hot-mix asphalt (HMA) design characteristics were analyzed in detail for different HMA surface mixtures at the Virginia Smart Road. The seven HMA wearing surface mixtures studied include five different Superpave™ mixtures, a stone mastic asphalt (SMA), and an open-graded friction course (OGFC). Mixture properties were measured from samples taken from each test section and compacted in the laboratory. The evaluation of the surface characteristics was based on measurements conducted using a locked-wheel trailer with the ASTM specified ribbed and smooth tires. Macrotexture measurements were conducted using a laser profile measurement device. Statistical tests indicate that, for the mixes studied, the roadway slope has insignificant effect on skid number measurements. Friction measurements are dependent on the tire used, surface texture, age in service, and temperature of the surface. The dependence of skid numbers on the measurement speed also varies with the type of tire used and surface conditions during testing. The relationship between SN and speed can be appropriately modeled using both exponential (Penn State model) and linear models. Regression analysis was performed on specific mixture properties, including voids in the mineral aggregate, total voids in the mixture, percentage passing the number 200 sieve, and binder type and content. The analysis indicated that there is a significant influence of these parameters on the ribbed tire skid resistance measurements and laser profile mean texture depth. These properties, however, were not sufficient to develop accurate models as to their effect on the smooth tire skid resistance measurements.

Keywords: Skid Resistance, Pavement Texture, Macrotexture, Pavement Surface Characteristics
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Effects of Microstructures on the Deformation Characteristics of Modified Asphalt Mixtures at High Temperature

Masato Murayama

e-mail: [e-mail]