Trb superpave Abstracts 2002

Professor Kenji Himeno

e-mail: [e-mail]
Department of Civil Engineering

Chuo University

1-13-27, Kasuga, Bunnkyo-ku, Tokyo, 112-8551, Japan

Tel& Fax [phone]

ABSTRACT

Experimental investigations were carried out for polymer modified binder (PMB) thin film and microtexture of the coarse aggregate’s surface, which are microstructure at an intermediate level of a few micrometers to several tens of micrometers considered to connect chemical phenomena and physical phenomena in modified asphalt mixtures. The microscopic observation of PMB by Styrene Butadiene Styrene block co-polymer (SBS) and measurement of viscoelasticity of the thin film were implemented. As a result, it was found that the thickness of binder films for measuring its viscoelasticity should not exceed 500m, and that the measured G*/sin  for thin films of 20m in thickness has a high correlation with the flow deformation resistance of the porous asphalt mixture at high temperature. This is because the morphology varies depending on the Colloidal Instability Index (Ci) of the base asphalt and the Melt Index (Mi) that is related to the molecular weight of SBS. Also, the microtexture of the coarse aggregate’s surface was measured and expressed in a form of Fractal Dimension. It was found that the fractal dimension had a high correlation with the flow deformation and the compaction properties of the porous mixtures.

KEY WORDS

microstructure, binder thin film, microtexture, morphology, polymer modified binder, coarse aggregate, laser displacement meter , fractal dimension, compaction, wheel tracking test, porous asphalt mixture

Return to Table of Contents

Evaluation of Performance of Full Depth Reclamation (FDR) Mixes

Rajib B. Mallick

Worcester Polytechnic Institute (WPI)

David S. Bonner

Worcester Polytechnic Institute (WPI)

Richard L. Bradbury

Jamie O. Andrews

Maine Department of Transportation
Prithvi S. Kandhal

National Center for Asphalt Technology (NCAT)

Edward J. Kearney

Gorman Brothers, Inc.

ABSTRACT

The Full Depth Reclamation (FDR), process consists of reclaiming all of the asphalt bound section along with a predetermined amount of underlying base, with some additive. FDR is particularly suitable for treating base problems related to deeper layers such as the base. The objectives of this study were to determine suitable compactive effort for designing FDR mixes, evaluate the benefits of using different types of additives in terms of improvement in the life of a pavement and determine suitable structural numbers for pavements recycled with different types of additives. The scope of work for this part of the study consisted of conducting Falling Weight Deflectometer (FWD), testing of an existing pavement before FDR, sampling of materials during FDR, determination of density of in-place material after compaction, compaction of loose mix in the laboratory, determination of density of compacted samples, conducting FWD on finished pavement, determination of resilient modulus of in-place cores and analyzing the data for determination of suitable number of gyrations, improvement in life of the pavement and structural numbers. From the results of comparison of in-place density and density of loose mix, and comparison of optimum fluid content and resilient modulus of laboratory samples compacted to 50 and 75 gyrations, it is concluded that samples be compacted to 50 gyrations during mix design, and that a minimum of 98 % of density of in-place loose mix samples, compacted to 50 gyration, be achieved in the field at the end of compaction. Comparison of cost for a specific amount of increase in life of pavement showed that for the options considered in this study, recycling with emulsion (3.4 %) and lime (2 %) is the most cost effective option. A visual evaluation of recycled sections after one year showed no significant distress in any section, except in the water section where a moderate amount of edge cracking was noted.

Key words: Full depth reclamation, performance, emulsion, gyratory, density
Return to Table of Contents

Evaluation of the Performance of Pavement Sections Constructed in Grand Teton National Park

Kenneth P. Thomas1, P. Michael Harnsberger2, and Raymond E. Robertson3
Western Research Institute, 365 North 9th Street, Laramie, WY 82072-3380

1 Phone [phone]; Fax [phone]; E-mail: [e-mail] (corresponding author)

2 Phone [phone]; Fax [phone]; E-mail: [e-mail]

3 Phone [phone]; Fax [phone]; E-mail: [e-mail]

ABSTRACT

The monitoring program associated with the polymer-modified and shale oil-modified asphalt pavements constructed in Grand Teton National Park consisted of an evaluation of the performance of the pavements with respect to in-service aging and ride performance. According to the PG grading procedure, the polymer-modified pavement was a PG 70-22 and the shale oil-modified pavement was a PG 64-22. At 98% design reliability, the grade that is recommended is PG 58-40. Thus, the two pavements do not satisfy the low-temperature (cracking) requirement, being too stiff, but exceed the high-temperature (rutting) requirement. In addition, evidence of moisture damage was not observed in either of the pavements.

With respect to ride performance, the extent of rutting observed for the two different pavements after seven years of service was negligible. Cracking was observed in both pavements after the second winter (1994-1995). However, at any particular point in time the polymer-modified pavement exhibited less cracking than the shale oil modified pavement. Evaluation of the cracks seemed to indicate that they were reflection of original cracks or thermal cracks. It was demonstrated that the development of the cracks was related not only to the number of times the pavement temperature exceeded the low-temperature CPG limit but also to the number of times the daily air temperature fluctuation exceeded a specified range and the low-temperature limit was the T_g of the binder.


Return to Table of Contents

Laboratory Simulation of Field Compaction Characteristics on Sandy Soils

W. Virgil Ping, Zenghai Yang

Department of Civil and Environmental Engineering

Florida A&M University - Florida State University

College of Engineering

Tallahassee, Florida 32310-6046

[phone] (Phone) [phone] (FAX)

e-mail: [e-mail]
Michael Leonard

HDR Engineering, Inc.

Jacksonville, Florida 32202-4327

Sastry Putcha

Florida Department of Transportation

Tallahassee, Florida 32399-0450

Abstract

Due to the development of much heavier earth moving and vibratory roller compaction equipment, soil compaction densities in the field are reaching levels that are not attainable in the laboratory. Higher compaction efforts, routinely seen in the field, not only result in higher unit weights but also lower optimum moisture contents than those found by the modified Proctor test. This paper presents an experimental study to evaluate field and laboratory compaction characteristics and to further study laboratory compaction techniques such as gyratory compaction, in addition to impact and vibratory compaction, for the laboratory simulation of field compaction of A-3 sandy soils. Field test sections were constructed using typical field compaction techniques of today. Earth pressure cells were installed at the base of each lift to monitor total vertical stresses. A series of laboratory gyratory compaction tests for A-3 soils were conducted. Factors including vertical pressure, gyration angle, and gyration numbers were evaluated for the effects on the dry unit weight. The gyratory compaction curves using 200 kPa vertical pressure, a 1.25-degree gyration angle, and 90 gyrations were close to the field compaction curves.

KEY WORDS: gyratory compaction, vibratory compaction, Proctor compaction, sand
Return to Table of Contents

Measuring and Defining Fatigue Behavior Of Asphalt Binders

Karen S. Bonnetti, Kitae Nam, Hussain U. Bahia

The Asphalt Pavement Research Group

Department of Civil and Environmental Engineering

The University of Wisconsin – Madison

2210 Engineering Hall

1415 Engineering Dr.

Madison WI, 53706

608) 265-4481

[e-mail], [e-mail], or [e-mail]
ABSTRACT

Asphalt is a visco-elastic material that portrays non-linear behavior. Previous studies have shown that the non-linearity of asphalt is an indicative of damage, and that it may be related to energy dissipation in damage. Fatigue damage is a distress mechanism observed in asphalt particularly at moderate to low temperatures. Under such conditions there appears to be a relationship between non-linearity, rate of energy dissipation, and fatigue damage. Preliminary studies have shown that unmodified asphalts are sensitive to fatigue and that the use of modifiers in asphalt binders can results in dramatic improvements in the binder’s response to fatigue. One of the major challenges encountered has been the lack of a definition of fatigue failure that is consistent with the actual performance of the material regardless of testing conditions. Superpave asphalt binder specification has made the evaluation of modified and neat asphalts less difficult, but the definition of failure for fatigue damage is still uncertain. A selected set of unmodified and modified binders were chosen and tested under a range of loading modes, stress or strain amplitudes, temperatures, and frequencies. The fatigue data was analyzed using the Dissipated Energy Ratio concept, and Np, the number of cycles to crack propagation, was used as the fatigue criterion for the analysis. The results indicate that using the initial dissipated energy per cycle (Wi) as the main independent variable for modeling fatigue of binders is a promising technique to normalize some of the testing conditions. The results show that using the parameter Np20, which is defined as the number of cycles at which the dissipated energy ratio show 20 % deviation form the no damage ratio, is a promising parameter to define failure. Using Np20 values it is found that all modification methods used show improvement in the fatigue behavior of un-modified asphalts. The level of improvement, however, is highly dependent on the modifier type and the testing conditions. Initial dissipated energy, testing frequency, and temperature are found to be important factors. It is recommended that if damage parameters are used in future specifications of binders, testing frequency and testing stress or strain should be carefully selected to represent pavement structural conditions and traffic speed.

Key Words: Fatigue cracking, Modified asphalt binders, Dissipated energy ratio, Time sweep test (DSR)
Return to Table of Contents

Micromechanical Analysis of the Viscoelastic Properties of Asphalt Concretes

A.T.Papagiannakis, A. Abbas and E.Masad

Washington State University
ABSTRACT

This paper describes a methodology for relating the microstructure of asphalt concretes to their viscoelastic behavior. Imaging techniques are used for capturing the asphalt concrete microstructure and the finite element method (FEM) is used for modeling its stress-strain behavior in the time domain. Aggregates are modeled as linear elastic, while the binder is modeled through mechanistic models as either linear viscoelastic or non-linear viscoelastic. The binder viscoelastic properties are input into the FEM algorithm using two methods, a built-in viscoelastic function and a userspecified material characterization subroutine. The latter handles non-linearity in an iterative piece-wise linear fashion, whereby the mechanistic binder model parameters are updated as a function of the strain level. For each strain level, mechanistic models are fitted to describe binder viscoelastic behavior based on Dynamic Shear Rheometer data. The two approaches used for specifying binder viscoelastic properties into the FEM algorithm were verified by comparing binder response predictions to direct measurements. Finally, the asphalt concrete microstructure model was verified by comparing FEM predictions of dynamic shear modulus and phase angle to measurements obtained using a Superpave Shear Tester.

KEYWORDS: asphalt binder, microstructure, finite element, constitutive modeling.
Return to Table of Contents

Three-Dimensional Aggregate Evaluation Using X-ray Tomography Imaging

L.B. Wang1, J.D. Frost2, L. Mohammad3, T.Y. Pang4
1 JFAP Assistant Professor, Department of Civil and Environmental Engineering
Louisiana State University/Southern University, Baton Rouge, LA 70803
2 Professor, School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA 30332
3 Associate Professor, Department of Civil and Environmental Engineering, Louisiana State University and Louisiana Transportation Research Center, Baton Rouge, LA 70803
4 Graduate Research Assistant, Department of Civil and Environmental Engineering
Louisiana State University and Louisiana Transportation Research Center, Baton Rouge, LA 70803
ABSTRACT

The paper presents a new method using x-ray tomography imaging for three-dimensional (3D) aggregate evaluations. The method reconstructs the 3D representation of individual particles and computes the specific surface area and the sphericity (a shape factor) of individual particles. Evaluation of a limestone aggregate in the sieve size range (3/8 in.- No.4) indicates that the specific surface area and the sphericity have a large variation among individual particles. However, the overall specific surface area of the aggregate particles within the same sieve size range can be accurately obtained using about 25-30 particles. It has been found that the specific surface area of the aggregates is much larger (84%) than that of the spheres of equivalent size. In addition, two dimensional (2D) image indices of shape and roughness including roundness, roughness and fractal dimension have been evaluated over both the cross-sections of an individual particle and the cross-sections of different particles. The comparison of the evaluations indicates that these 2D quantities can be statistically evaluated from about 50-100 cross-sections from either an individual particle or different particles.

Return to Table of Contents

Characterization of Aggregate Shape Using Fourier Analysis and Digital Imaging Technique

Mr. Ramitha Wettimuny

Research Assistant, Computer and Electrical Engineering

115 Center for Advanced Materials Processing (CAMP) Building

Clarkson University, Potsdam, NY 13699-5710

Phone: [phone]

E-Mail: [e-mail]

And

Corresponding Author:

Dr. Dayakar Penumadu

Associate Professor, Civil and Environmental Engineering

128 Rowley Laboratories

Clarkson University, Potsdam, NY 13699-5710

Phone: [phone]

Fax: [phone]

E-Mail: [e-mail]

ABSTRACT

The shape and texture of gravel and sand have important influence on the behavior of hot mix asphalt. Recent improvements in acquisition of digital images and their analysis, provides unique opportunities for describing shape and texture of particles in an automated fashion. Shape analysis of fine and coarse aggregate particles is investigated in this study using fast Fourier transform of digital images. Two dimensional digital images are captured by a charge-coupled device camera with appropriate optics and image analysis software. The geometric signature of each shape is extracted by measuring the distance between its centroid and the boundary at constant increment of angles. Using this shape profile of length vs. angle data for a given aggregate particle, Fast Fourier Transform is used to evaluate its spectral information. The number of highest amplitude harmonics required for accurate profile regeneration is investigated. Shape of a given aggregate particle is reconstructed using Inverse Fourier Transforms using limited number of significant harmonics. A parameter that can quantify the error between regenerated and original profiles is proposed. Using this value, two shape parameters are defined to describe the overall shape and the ruggedness of a particle. A procedure of quantitatively describing the roundness/angularity of aggregate shape is presented. The analysis is extended to three dimensions using orthogonal views, and the results are compared with existing methods using flatness, elongation, and sphericity.

Return to Table of Contents

Construction-Related Asphalt Concrete Pavement Temperature and Density Differentials

Kim A. Willoughby

Washington State Department of Transportation

P.O. Box 47365

Olympia, WA 98504-7365

Phone: [phone]

Fax: [phone]

[e-mail]
Jeff S. Uhlmeyer

Washington State Department of Transportation

P.O. Box 47365

Olympia, WA 98504-7365

Phone: [phone]

Fax: [phone]

[e-mail]
Joe P. Mahoney

Civil and Environmental Engineering

University of Washington

Box 352700

Seattle, WA 98195-2700

Phone: [phone]

Fax: [phone]

[e-mail]

Keith W. Anderson

Washington State Department of Transportation

P.O. Box 47365

Olympia, WA 98504-7365

Phone: [phone]

Fax: [phone]

[e-mail]
Linda M. Pierce

Washington State Department of Transportation

P.O. Box 47365

Olympia, WA 98504-7365

Phone: [phone]

Fax: [phone]

[e-mail]

ABSTRACT

The Washington State Department of Transportation (WSDOT) has conducted an examination of temperature differentials in hot-mix asphalt paving over four construction seasons. From these studies, it has been found that low-density areas can be caused by temperature differentials in the mat.

The study summarized in this paper is based on an examination of 17 projects during the 2000 WSDOT paving season to determine density differentials in the mat with a “density profile”. A density profile is a series of density readings taken in a longitudinal direction over a 15 meter (50 foot) section through a low temperature area. From this collection of density readings, the density range (difference between the maximum and minimum readings) and density drop (difference between the average and minimum readings) are determined. The density range and drop are used to determine if low temperature areas have been affected by inadequate compaction. The criterion set forth by WSDOT included temperature differentials greater than or equal to 14ºC (25°F), a maximum density range of 96 kilograms per cubic meter (kg/m³) (6.0 pounds per cubic foot (pcf)), and a maximum density drop of 48 kg/m³ (3.0 pcf). Evaluation of the density profiles showed that when the temperature differential exceeded 14°C (25ºF), 89 percent of the density profiles failed the density criteria and only 19 percent failed the density criteria when the temperature differential was less than 14ºC (25ºF). It was found that pavements that experienced large temperature differentials during placement produced substantial density differentials.
Return to Table of Contents

Prediction of Daily Temperature Profile in Flexible Pavements

Brian K. Diefenderfer

Former Graduate Research Assistant

Virginia Tech Transportation Institute

Project Engineer

CONCORR, Inc.

44633 Guilford Dr.

Suite 101

Ashburn, VA 20147

Tel: [phone], Fax: [phone]

e-mail: [e-mail]

Imad L. Al-Qadi

Professor

The Via Department of Civil and Environmental Engineering

200 Patton Hall

Blacksburg, VA 24061-0105

Tel: [phone], Fax: [phone]

e-mail: [e-mail]
Stacey D. Reubush

Graduate Research Assistant

Virginia Tech Transportation Institute

3500 Transportation Research Plaza

Blacksburg, VA 24061-0536

Tel: [phone], Fax: [phone]

e-mail: [e-mail]

ABSTRACT

Hot-mix asphalt (HMA) pavements comprise a majority of the primary highways in the United States. These primary roads are subjected to heavy loading that can cause significant damage to the flexible pavement. As HMA is a viscoelastic material, the structural or load-carrying capacity of the pavement varies with temperature. Thus, to determine flexible pavement in-situ strength characteristics, it is necessary to be able to accurately predict or estimate the temperature distribution within the HMA layers. The majority of previously published research on pavement temperature prediction has focused on predicting the annual maximum or minimum pavement temperature so as to recommend a suitable asphalt binder performance grade. However, modeling the pavement temperature on a daily or hourly basis has only been recently investigated. To determine the pavement temperature profile, the influence of ambient temperature and seasonal changes must be understood such that the effects of heating and cooling trends within the pavement structure can be quantified. In addition, the influence of different pavement structures on the temperature distribution within the pavement structure must be determined. This paper presents the temperature profile monitoring of flexible pavements at the Virginia Smart Road from March 2000 through May 2001. Developed models to predict the daily maximum and minimum temperature at depths to 0.188m within the pavement structure are presented. In this paper, a single model each for daily maximum and minimum pavement temperatures is presented for application. The model was found accurate when evaluated across several different pavement sections having unique material properties.

Keywords: instrumentation, pavement temperature, temperature modeling, thermocouple
Return to Table of Contents

Procedure for Monitoring and Improving the Effectiveness of Quality Assurance Specifications

Sutharin Pathomvanich, PhD

Department of Civil Engineering

Kasetsart University

50 Phaholyothin Road

Chatujak, Bangkok, Thailand 10900

Phone: [phone]

Fax: [phone]

[e-mail]

Fazil T. Najafi, PhD

Department of Civil and Coastal Engineering

345 Weil Hall

University of Florida

Gainesville, Florida 32611-6580

Phone: [phone]

Fax: [phone]

[e-mail]

Peter A. Kopac, MSCE, PE

Federal Highway Administration

6300 Georgetown Pike

McLean, Virginia 22101

Phone: [phone]

Fax: [phone]

[e-mail]

ABSTRACT

Writing quality assurance specifications is as much an art as a science. The specifications must be introduced and monitored in the field before it can be concluded they are providing the level of construction quality and performance that is desired. Even those specifications that have proven their adequacy must continue to be monitored in a changing construction environment. Little guidance currently exists, however, on how a highway agency can objectively assess and/or monitor its quality assurance specifications.

Presented is a procedure that responds to this need. The procedure can be used to assess how well a specification is working or to monitor the specification to assure continuing effectiveness. A major benefit is that the procedure can identify inconsistencies that should be corrected if the specification is to be truly effective. Continuous quality improvement is thus made possible. Emphasized throughout is the need for agencies to have good pavement or asset management systems and databases.

The procedure was tested on a state highway agency’s asphalt pavement specifications. It was concluded the effectiveness of the agency’s specifications could be improved. It is likely some of the suggested improvements also apply to other agencies. Among these is the need for all to know what quality level the agency wants, and for the agency to clearly state this in its specifications. In most cases, essentially the same quality level should be specified for a quality characteristic, regardless of the number of acceptance samples (n) to be taken from a lot. Additionally, if specifications are to be not only effective but cost-effective as well, establishing the optimal quality level becomes paramount.

Return to Table of Contents

Rutting of Asphalt Pavements in Manitoba and Relationship To Strength and Deformation Properties

Myron Thiessen

Department of Civil Engineering

University of Manitoba

Winnipeg, Manitoba

Canada, R3T 5V6

Tel: [phone]

Fax: [phone]

E-mail: [e-mail]

Ahmed Shalaby

Department of Civil Engineering

University of Manitoba

Winnipeg, Manitoba

Canada, R3T 5V6

Tel: [phone]

Fax: [phone]

E-mail: [e-mail]

Leonnie Kavanagh

Materials and Research Branch

Manitoba Department of Transportation and Government Services

12th Floor, 215 Garry Street

Winnipeg, Manitoba

Canada, R3C 3Z1

Tel: [phone]

Fax: [phone]

E-mail: [e-mail]

ABSTRACT

This research investigates the rutting performance of asphalt pavements in Manitoba. The aim of the research is to characterize the relationship between material properties and strength parameters measured in the laboratory to observed rutting behavior in the field. Experience gained in this area will serve to help in the selection of suitable mix designs that are more resistant to rutting. Pertinent information, including traffic data, as-constructed pavement properties, and pavement rut depth, were collected for nine pavement sites. Twenty-one core samples were also obtained from each site at three randomly selected locations within each section. Twelve cores from each site were tested for physical mixture properties while three replicate samples per site were tested for strength and deformation parameters using a modified form of the indirect tensile strength test. In this procedure, test specimens are loaded along their diametral axis until failure at a loading rate of 0.1 mm/minute and a temperature of 25ºC. Miniature linear variable differential transducers mounted directly on the central portion of the sample measured the lateral and axial deformations throughout the test. Regression analysis was employed to relate the rutting data from each pavement section to physical mixture properties and strength parameters. Results of the analysis clearly show that measured deformations and Poisson’s ratio obtained from the indirect tensile test are closely related to rutting in the field. Based on these results, the modified indirect tensile test shows promise as a means to evaluate mixture strength and to identify rutting susceptibility of asphalt mixtures.

Return to Table of Contents

The Pavement Design, Construction, and Materials Enterprise at Michigan Technological University

James W. Boggs

Graduate Student

Civil and Environmental Engineering

Michigan Technological University

Houghton, Michigan 49931

[e-mail]

[phone] phone

[phone] fax

George R. Dewey

Associate Professor

Civil and Environmental Engineering

Michigan Technological University

Houghton, Michigan 49931

[e-mail]

[phone] phone

[phone] fax

R. Chris Williams

Assistant Professor

Civil and Environmental Engineering

Michigan Technological University

Houghton, Michigan 49931

[e-mail]

[phone] phone

[phone] fax

Kris G. Mattila

Assistant Professor

Civil and Environmental Engineering

Michigan Technological University

Houghton, Michigan 49931

[e-mail]

[phone] phone

[phone] fax

ABSTRACT

A project-based student enterprise program was established at Michigan Technological University as part of an National Science Foundation funded effort related to reform of engineering education. The enterprise program represents a separate degree track available in all departments of the College of Engineering. The Pavement Design, Construction, and Materials (PDCM) Enterprise was established in the Civil and Environmental Engineering Department as part of the Thompson Scholars program. This asphalt paving industry sponsored scholarship program will grow to a total of 100 undergraduate and six graduate scholarships. The PDCM Enterprise is composed of a team of students that work in a business-like setting on projects directly related to asphalt pavements. In addition to their project activities, students are required to participate in paid summer internships in associated industries and organizations. An Advisory Board composed of industry and government leaders meets periodically with the PDCM Enterprise to provide advice, guidance, and feedback to the students and associated faculty. The team project activities of the PDCM Enterprise prepares graduates for careers in the pavement engineering field with knowledge and skills well beyond their peers in the traditional civil engineering curriculum.

Return to Table of Contents

A Laboratory Study of Full Depth Reclamation (FDR) Mixes

Rajib B. Mallick

CEE Department

Worcester Polytechnic Institute (WPI), 100 Institute Road

Worcester, MA 01609

508 831 5289, Fax: [phone], [e-mail]
Matthew R. Teto

Worcester Polytechnic Institute (WPI)

Prithvi S. Kandhal

Elton Ray Brown

National Center for Asphalt Technology (NCAT)
Richard L. Bradbury

Maine Department of Transportation (ME DOT)

Edward J. Kearney

Gorman Brothers, Inc.

Full depth reclamation (FDR) is the technique of in-place recycling of the asphalt bound layer of a pavement along with part of the underlying unbound layer to produce an improved base material. Several New England states, including the Maine Department of Transportation (DOT) are involved in significant amounts of FDR work. The objective of this study was to develop a mix design system for FDR and evaluate the performance of designed reclaimed materials from western part of Maine. Mixes were prepared in the laboratory, and samples were compacted with Superpave gyratory compactor. The samples were then tested for bulk specific gravity and resilient modulus. Samples of mixes prepared with asphalt emulsion, water, emulsion plus lime, emulsion plus cement and emulsion plus lime and cement were also tested for resilient modulus at different cure times and for shear strength. Rut tests were also conducted with the samples under water to evaluate stripping potential of the different mixes. Test results show that maximum density and resilient modulus criteria can be used to select the optimum additive content for water and asphalt emulsion mixes. Comparison of performance testing results show that mixes with additives develop strength faster and show significantly higher shear strength and stripping resistance compared to mixes with water only. For the materials tested, addition of lime and cement with asphalt emulsion seems to increase the rate of gain in strength and hence result in faster curing, and seems to increase the shear strength as well as stripping resistance. It is recommended that FDR sections with asphalt emulsion, lime and cement be constructed and evaluated for in-place performance.
Key words: Full depth reclamation, emulsion, curing, resilient modulus
Return to Table of Contents

Analysis of The Statistical Distribution of Failure Stress Values Determined Using The Superpave Direct Tension Test

Raj Dongré, Ph. D

Consultant

Federal Highway Administration

6300, Georgetown Pike

McLean, VA –22101

[phone]

E-mail: [e-mail]
Charles Antle, Ph. D

Professor Emeritus

Penn State University

2302 West Branch Road

State College, PA 16801

[phone]

E-mail: [e-mail]

Abstract

A statistically robust method was developed based on the Weibull distribution to identify and eliminate outliers from the failure stress determinations. The method is applicable to any failure stress data set that follows the Weibull distribution, but in this paper it was developed for the AASHTO standard test method for conducting the DTT test. A large number of stress at failure measurements with the DTT were made in the course of instructing the users of this device. These data, all for the same asphalt, provided the means for studying the nature of the distribution of the breaking strength of these asphalt specimens. There were over 900 data points in this training database. It was found that the current AASHTO practice of eliminating the lowest two stress values is reasonable. However, it is an arbitrary method that may lead to problems in the future. Based on the results of this study, the procedure developed here is recommended for use and implementation in the next AASHTO version of the DTT standard.

Return to Table of Contents

Application of The Rolling Dynamic Deflectometer To Project-Level Pavement Studies

J. L. Y. Lee, K.H. Stokoe, II, M.R. Murphy, and D.K. Rozycki