Trb superpave Abstracts 2002

ABSTRACT

The Rolling Dynamic Deflectometer (RDD) is a relatively new nondestructive testing device for measuring continuous deflection profiles along pavements. The basic operational principals are: 1. subject the pavement surface to a known dynamic loading at a single frequency, and 2. measure the response of the pavement surface at the predetermined frequency with an array of rolling sensors. The ability to perform continuous deflection profiling with the RDD is a key attribute of the equipment in pavement infrastructure studies. Based on numerous field measurements taken at different highway test sections in Texas and Pennsylvania, several applications of the RDD in project-level studies are presented. The utility of continuous RDD profiles is shown for: 1. evaluating the performance of all transverse cracks and joints in a pavement section, 2. delineating changes in pavement cross-sections, 3. evaluating mid-slab action and/or the lack of mid-slab action, 4. sub-dividing pavement sections into similar subsections based on surface deflections and 5. performing crack surveys.
KEYWORDS: Continuous Profiling, Nondestructive Testing, Deflection Testing, Rolling Dynamic Deflectometer, Rigid Pavements
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Evaluation of Fatigue Healing Effect of Asphalt Concrete by Pseudo Stiffness

Zhiming Si, Ph.D., E.I.T.

Texas Department of Transportation

Austin, TX 78713

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Fax: [phone]

Email: [e-mail]

Dallas N. Little, Ph.D., P.E.

Texas Transportation Institute

Texas A&M University

College Station, TX 77843-3135

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Fax: [phone]

Email: [e-mail]
Robert L. Lytton, Ph.D., P.E.

Texas Transportation Institute

Texas A&M University

College Station, TX 77843-3135

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Fax: [phone]

Email: [e-mail]

ABSTRACT

Pseudo strain concept based on the extended nonlinear elastic-viscoelastic correspondence principle has been demonstrated in this research to be an appropriate and efficient method to evaluate both microdamage and healing during the fatigue damage process. Pseudo stiffness can be used to monitor microdamage and healing during the fatigue test. Pseudo stiffness decreases consistently with increasing number of loading cycles, indicating that the microdamage occurs during the fatigue test. The significant recovery of pseudo stiffness after rest periods indicates that there is a strong healing due to rest periods. The effects of hydrated lime on fatigue microdamage and healing have also been evaluated based on pseudo stiffness recovery. The impact of healing during rest periods is evident and substantial. The degree of healing is mixture dependent. The ability of a mixture to heal is largely related to binder properties. The addition of hydrated lime to the mixtures tested generally improved the healing potential of the mixtures. In general, the stiffer mixtures have better healing. In addition, the longer rest period results in higher healing. The mechanism of healing is evaluated by two theories. The initial healing rate is governed by the nonpolar surface energy, and the final healing rate is governed by the polar surface energy.

KeyWords: Fatigue, Microdamage, Healing, Pseudo Strain, Pseudo Stiffness
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Measurement of Vertical Compressive Stress Pulse in Flexible Pavements and Its Representation For Dynamic Loading Tests

Amara Loulizi, Research Scientist

Virginia Tech Transportation Institute

3500 Transportation Research Plaza

Blacksburg, VA 24061

Tel: [phone], Fax: [phone]

e-mail: [e-mail]

Imad L. Al-Qadi, Professor

The Via Department of Civil and Environmental Engineering

200 Patton Hall

Virginia Polytechnic Institute and State University

Blacksburg, VA 24061-0105

Tel: [phone], Fax: [phone]

e-mail: [e-mail]
Samer Lahouar, Graduate Research Assistant

Virginia Tech Transportation Institute

3500 Transportation Research Plaza

Blacksburg, VA 24061

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e-mail: [e-mail]

Thomas E. Freeman

Senior Research Scientist

Vermont Department of Transportation

530 Edgemont Road

Charlottesville, VA 22903

Tel: [phone], Fax: [phone]

e-mail: [e-mail]

Testing at the Virginia Smart Road allowed the determination of the vertical compressive stress pulse induced by a moving truck and by FWD loading at different locations beneath the pavement surface. Testing was performed on 12 different flexible pavement sections. Stress and temperature were measured using pressure cells and thermocouples; respectively, which were installed during construction of the road. The target testing speeds were 8km/h, 24km/h, 40km/h, and 72km/h. The considered depths below the pavement surface were 40mm, 190mm, 267mm, 419mm, and 597mm. It was found that a haversine or a normalized bell-shape equation represent well the measured normalized vertical compressive stress pulse for a moving vehicle. Haversine duration times varied from 0.02s for a vehicle speed of 70km/h at a depth of 40mm to 1s for a vehicle speed of 10km/h at a depth of 597mm. For the FWD loading, a haversine with a duration of 0.03s was found to approximate the induced stress pulse at any depth below the pavement surface. Currently, laboratory dynamic testing on hot-mix asphalt (HMA) specimens is performed using a haversine wave at loading duration of 0.1s. Since HMA is a viscoelastic material, the loading time affects its properties and therefore, it is recommended to reduce the loading time of HMA dynamic tests to 0.03s to better match loading times obtained from moving trucks at average speed and from FWD testing.

Keywords: Flexible Pavements, Instrumentation, Dynamic Loading, Stress Pulse.
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A Probabilistic Model for Prediction of Asphalt Pavement Crack Depths

Mr. M. Wasantha Kumara,

Graduate Research Assistant,

Department of Civil and Environmental Engineering

University of South Florida, ENB 118

4202 East Fowler Avenue

Tampa, FL 33620-5350

Ph: [phone]

Fax: [phone]

Email: [e-mail]
Dr. M. Gunaratne, Ph.D., Professor,

Department of Civil and Environmental Engineering

University of South Florida, ENB 118

4202 East Fowler Avenue

Tampa, FL 33620-5350

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Fax: [phone]

Email: [e-mail]

Dr. J. J. Lu, Ph.D., Associate Professor.

Department of Civil and Environmental Engineering

University of South Florida, ENB 118

4202 East Fowler Avenue

Tampa, FL 33620-5350

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Fax: [phone]

Email: [e-mail]

Mr. B. Dietrich,

State Pavement Evaluation Engineer,

Florida Department of Transportation,

Tallahassee, FL

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Email: [e-mail]

Abstract

Surface-initiated longitudinal wheel path cracking induced by tensile stresses under repeated radial truck tires is the predominant form of distress that appears on Florida’s asphaltic road surfaces. Pavement damage under such loads can be considered as a cumulative damage process because the irreversible fracturing at each cyclic operation accumulates until the surface layer can no longer perform satisfactorily. Hence, the crack life of a pavement is dependent on the accumulated axle loads (ESALs), mixture properties and the support condition. In this paper, the authors discuss how the cumulative ESALs at failure, indicated by annually recorded crack indices (CI) in the FDOT pavement management (PM) database, are used to establish relationships for the mean and variance of ESALs for a given crack depth. Then, a Markov probabilistic approach is followed to develop probability distribution of crack depths with respect to cumulative ESALs. The model parameters such as transitional probabilities corresponding to specific damage states are evaluated from the above ESAL statistics. Finally, the developed model is validated using data from field core samples.

Keyword: surface cracks, longitudinal cracks, Markov probabilistic method, Pavement Management, Crack growth

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An Analytically-Based Approach to Rutting Prediction

John T. Harvey, Research Engineer

Tel: [phone] [e-mail]

Irwin Guada, Junior Development Engineer

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Lorina Popescu, Junior Development Engineer

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Carl L. Monismith,

Tel: [phone] [e-mail]

University of California, Berkeley

Pavement Research Center, Institute of Transportation Studies

1353 S 46th St., Bldg 480

Richmond, Ca 94804

Fax: [phone]
John A. Deacon, Professor Emeritus

Department of Civil Engineering

University of Kentucky

Lexington, Kentucky

[e-mail]

ABSTRACT

This paper presents the results of an analytically-based (mechanistic-empirical), procedure to estimate the development of rutting in asphalt concrete pavements both as a function of traffic loading and environment relative to its influence on pavement temperatures. The procedure utilizes permanent strain determined for a representative asphalt concrete mix as function of load repetitions, shear stress and elastic shear strain. It combines multilayer elastic analysis for determining key shear stresses and strains in the asphalt concrete resulting from traffic loading to be used in the permanent strain expression with a time-hardening procedure for the accumulation of permanent strain both as a function of traffic loading and environment. The WesTrack test sections were used to calibrate the methodology and results of rutting predictions are included for four different test sections from that experiment. Based on the results of the regression analyses, an expression is presented which can be used to determine coefficients for use in the permanent strain expression which reflect the permanent deformation characteristics of a specific mix as measured in repeated simple shear test at constant height (RSST-CH). In addition to the WesTrack examples, results are also presented illustrating the use of the approach to predict rutting development in a controlled loading condition at 50º C (122º F) using the Heavy Vehicle Simulator.

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Analysis of Bituminous Crack Sealants by Physico-Chemical Methods and its Relationship to Field Performance
J-F. Masson, Corresponding author

Peter Collins, Jim Margeson, Gary Polomark

Institute for Research in Construction

National Research Council of Canada

Ottawa, Ontario, Canada, K1A 0R6

Phone [phone]; fax [phone]

[e-mail]
ABSTRACT

Bituminous crack sealants were analyzed by viscometry, fluorescence microscopy, infrared spectroscopy, thermogravimetry, modulated differential scanning calorimetry and low temperature tensile testing. The results indicate that sealants are blends of bitumen, oil, copolymer and filler. Upon blending, these components produce a three phase system that consists of a polymer-modified bitumen (PMB) matrix, a filler, and a filler-PMB interface. Spectroscopy and microscopy indicate that the PMB phase is rich in styrene-butadiene type copolymer, that the filler is recycled rubber, sometimes mixed with calcium carbonate, and that the interface depends on the filler and the oil content in the sealant. The physico-chemical methods were used to predict the short- and medium-term performance of sealant mixtures. The short-term performance predicted from viscometry and microscopy correlated well with the 1-year field performance of the sealants. Sealants showed two glass transition temperatures (Tg’s), and a reasonable correlation was also found between the low temperature Tg and medium-term performance in a wetfreeze climate. However, because Tg measurements do not account for stress relaxation and aging effects, correlation was not perfect.

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Wavelet-based 3D Descriptors of Aggregate Particles

Hyoungkwan Kim: Graduate Research Assistant

Department of Civil Engineering, The University of Texas at Austin, ECJ 5.200, Austin, TX. 78712-1076

Tel: [phone], Fax: [phone], Email: [e-mail].
Carl T. Haas: Associate Professor

Department of Civil Engineering, The University of Texas at Austin, ECJ 5.200, Austin, TX. 78712-1076

Tel: [phone], Fax: [phone], Email: [e-mail].
Alan F. Rauch: Assistant Professor

Department of Civil Engineering, The University of Texas at Austin, ECJ 9.227, Austin, TX. 78712-1076

Tel: [phone], Fax: [phone], Email: [e-mail].
: Staff Engineer

GeoSyntec Consultants, Boxborough, MA, 01719

Tel: [phone], Fax: [phone], Email: [e-mail].
ABSTRACT

Morphological characteristics of stone aggregates, including particle shape, angularity, and surface texture, have a significant impact on the performance of hot mix asphalt materials. To accurately identify and quantify these critical aggregate characteristics, well-defined particle descriptors are essential. Moreover, because a large number of irregular particles must be assessed to adequately characterize an aggregate material, descriptors that can be quantified with automated machines are preferred. In processing true 3D data from a laser scanner, wavelet-based 3D particle descriptors are proposed as a way to characterize individual stone particles. Aided by the multiresolution analysis feature of the wavelet transform, these descriptors provide a generalized, comprehensive, and objective way of describing aggregates. This approach was implemented in conjunction with an automated laser scanning device built for rapidly characterizing the size and shape properties of aggregate samples. Tests with this equipment have produced data that show strong correlations between the wavelet-based particle descriptors and visual perceptions of the aggregate morphological properties. These results demonstrate that the wavelet-based approach is a promising method for quantifying these important aggregate properties.

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WesTrack Fatigue Performance Prediction Using Miner’s Law

Bor-Wen Tsai, Post-Doctoral Researcher

University of California, Berkeley

Institute of Transportation Studies, Pavement Research Center

1353 S. 46th St., Bldg. 480

Richmond, CA 94804

[phone] FAX: [phone]

[e-mail]
John T. Harvey, Associated Research Engineer

University of California, Berkeley

Institute of Transportation Studies, Pavement Research Center

1353 S. 46th St., Bldg. 480

Richmond, CA 94804

[phone] FAX: [phone]

[e-mail]

Carl L. Monismith, Professor Emeritus of Civil Engineering

University of California, Berkeley

Institute of Transportation Studies, Pavement Research Center

1353 S. 46th St., Bldg. 452 Rm.109

Richmond, CA 94804

[phone] FAX: [phone]

[e-mail]
ABSTRACT

The objectives of this paper are to present an approach using statistical analysis and Miner’s Law, and to use it to predict the fatigue performance (crack initiation) of the WesTrack test sections. A strain function, calculated by a layered-elastic program, was statistically determined in terms of temperature at the bottom of the asphalt layer, temperature gradient, subgrade modulus, air-void content and asphalt content. With integration of laboratory fatigue test results, strain calculation, and Miner’s Law, the methodology produces the output in terms of cumulative fatigue damage versus cumulative repetitions for both wander and nowander cases. Lack of consideration of non-linear stiffness deterioration of asphalt concrete, crack propagation and an appropriate correction factor makes the long term fatigue performance prediction conservative and not fully compliant with the condition survey data from WesTrack. The simulation indicated that the WesTrack coarse mixes took longer to initiate fatigue cracks than the fine and fine-plus mixes, but may propagate cracks faster in cold weather.

Key Words: pavements, fatigue performance, Miner’s Law, crack initiation, WesTrack.
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