Trb superpave Abstracts 2002

ABSTRACT

This research study had a primary objective: to recommend a fundamentally based laboratory Simple Performance Test (SPT) for permanent deformation evaluation to be used within the Superpave volumetric mixture design procedure. This SPT was intended to provide accurate correlation to field rutting performance. Two tests are discussed in this paper. These are the repeated load permanent deformation test, and the static creep / flow time test. The tests were evaluated using mixtures and performance data from three experimental sites: the Minnesota Road Project (MnRoad), the Federal Highway Administration (FHWA) Accelerated Loading Facility Study (ALF), and the FHWA Performance-Related Specifications Study (WesTrack). Several parameters were evaluated from each test. Two tertiary flow laboratory response parameters stood out in the study as having excellent correlation with field rut depth data: the flow number from the repeated load test and the flow time from the static creep test. The two parameters were found to be repeatable, reliable in distinguishing between a wide range of asphalt mixtures, and sensitive to different testing variables. Both of these parameters / tests were recommended for further evaluation and follow up validation testing.
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Effect of Fine Aggregate Angularity (FAA) on Compaction and Shearing Resistance of Asphalt Mixtures
Authors: Anthony D. Stakston, Jared J. Bushek, and Hussain U. Bahia
The University of Wisconsin Asphalt Group

Department of Civil and Environmental Engineering

1415 Engineering Dr. 2210 Engineering Hall

Madison, WI 53706

Abstract

This study was conducted to evaluate the effect of Fine Aggregate Angularity (FAA) on the densification characteristics of asphalt mixtures using the Superpave Gyratory Compactor (SGC). Aggregates from three different sources used in production of Superpave mixtures in Wisconsin were used. From each source a fine gradation and an coarse shaped gradation was included. To vary the FAA values of the fine aggregates, the proportions of the manufactured sand to the natural sand from each source was varied while keeping the same overall gradations. A range of FAA values between 40 and 48 for the sources was achieved. Keeping all other mixture variables constant, the mixtures were compacted in a SGC equipped with a special device called the Gyratory Load Plate Assembly to measure the densification and the shear force required for compaction of each mixture. Densification data were analyzed to estimate the effect of the FAA on the densification to 92% G_mm, assumed to represent resistance of mixture to construction compaction, and to densification above 92% G_mm, assumed to represent mixture resistance to traffic.

Results indicate a consistent trend of higher resistance to compaction with higher FAA values. Mixtures with higher FAA require higher compaction effort as measured by densification rate and shear force required for gyrating. Resistance to densification above 92% G_mm, assumed to represent traffic, shows inconsistent trends. For one source of aggregates the increase in FAA resulted in less resistance to densification and shear distortion above 92% G_mm. Results show that the sensitivity of mixture response variables to change in FAA values is highly dependent on source of aggregates and on the gradation. It is therefore recommended that mixture design be based on limits of the densification characteristics rather than a target FAA value for all mixture types.
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Examination of Aggregate Degradation and Effect on Volumetric Properties

Gregory A. Sholar

352.337.3278

[e-mail]
Gale C. Page

352.337.3208

[e-mail]
James A. Musselman

352.337.3150

[e-mail]
Florida Department of Transportation

2006 NE Waldo Road

Gainesville, FL 32609

Fax: [phone]

ABSTRACT

The reduction in the asphalt mixture properties air voids and voids in the mineral aggregate (VMA) that occurs during the production process has partially been attributed to a rounding/breakdown of the aggregate particles in the mixture. This study was initiated to relatively quantify this phenomenon between aggregate types. For this study, three different asphalt mixtures were sampled and tested at various points during the production sequence to ascertain the magnitude of aggregate breakdown and the corresponding effect on asphalt mixture properties. Aggregate gradations were obtained from the following points in the production sequence: 1) belt-cut samples, 2) asphalt mixture from the truck bed, 3) behind the asphalt paver at the roadway but prior to compaction, 4) after roller compaction at the roadway, and 5) from gyratory compacted specimens at the asphalt plant. Between 0.6% and 1.5% dust was generated in the drum. The gyratory compactor generated 0.8% dust for the granite mixture and approximately 1.5% dust for the limestone mixtures. Roadway compaction resulted in similar breakdown to the gyratory compactor. The Los Angeles abrasion test results for each predominant aggregate type correlated well with the amount of aggregate breakdown observed. The three mixtures were reproduced in the lab with varying percentages of dust to examine the effects on volumetric properties. In general, results indicate that removing 1% dust will increase air voids by approximately 0.8%, increase VMA by 0.5% and decrease voids filled with asphalt (VFA) by 5% at the design level of gyrations.

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Quantification of Coarse Aggregate Angularity Based on Image Analysis

Chetana Rao – Senior Research Engineer

ERES Consultants,

A Division of Applied Research Associates, Inc.

505 W. University Ave.

Champaign, IL 61820

Ph: [phone] / (Fax: [phone])

E-mail: [e-mail]
Dr. Erol Tutumluer – Assistant Professor

(CORRESPONDING AUTHOR)

Department of Civil and Environmental Engineering

University of Illinois at Urbana-Champaign

205 North Mathews

Urbana, IL 61801

Ph: [phone] / (Fax: [phone])

E-mail: [e-mail]
In Tai Kim – Graduate Research Assistant

Department of Civil and Environmental Engineering

University of Illinois at Urbana-Champaign

205 North Mathews

URBANA, IL 61801

Ph: [phone] / (Fax: [phone])

E-mail: [e-mail]

ABSTRACT

Aggregate angularity affects the shear strength properties of asphalt concrete and granular base layers in pavements. It also improves aggregate interlock and load transfer properties of jointed concrete pavements. This paper presents the development of a quantifiable index based on image analysis to characterize the angularity of coarse aggregate used in pavement layers. The new angularity index (AI) was developed as part of the University of Illinois Aggregate Image Analyzer and the procedure was calibrated for two aggregate samples, rounded gravel and crushed stone, which possess the two extremes of particle angularity. A statistical study demonstrated that the AI computation technique developed is not only able to distinguish crushed stone from gravel but also is robust enough to give similar AI values regardless of the particle size and orientation. Furthermore, the crushed stone and gravel samples together with a 50-50 blend of the two samples by weight were tested for shear strength under triaxial loading conditions. The AI value computed for these samples could be correlated to the angle of internal friction and thus the shear strength properties of the samples. The AI distributions of representative aggregate samples from Illinois, crushed gravel, limestone, and dolomite, were also computed. The newly developed index has also demonstrated the capability to distinguish between crushed stone and crushed gravel samples. With the use of this AI value as a measure of aggregate angularity, pavement engineers can objectively quantify the influence of aggregate angularity on asphalt concrete (AC), Portland cement concrete (PCC), and granular mix performance and thereby establish meaningful criteria relating aggregate properties to performance indicators.

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A Performance-Graded Binder Specification for Surface Treatments

Roberto Barcena 1

Amy Epps 2

Darren Hazlett3

1. 
   Research Assistant, Texas Transportation Institute, 501H CE/TTI Building, 3136 TAMU, College Station, TX 77843-3136, [phone], Fax [phone],
   Email: [e-mail]
   
2. 
   Assistant Professor, Texas A&M University, 503F CE/TTI Building, 3136 TAMU, College Station, TX 77843-3136, [phone], Fax [phone],
   Email: [e-mail]
   
3. 
   Supervising Chemical Engineer, Construction Division, Texas Department of Transportation. 2311 W. Rundberg Lane, Metric building #8, Suite 100, Austin, TX 78758, [phone], Fax [phone], Email: [e-mail]
   

ABSTRACT

Surface treatments have been used by many government agencies as part of their maintenance and rehabilitation programs to improve surface quality and extend the service life of pavements. Traditional specifications for surface treatment binders failed to characterize materials across the entire spectrum of temperatures experienced during production and construction and in-service and required properties that were not directly related to performance. The Superior Performing Asphalt Pavements (Superpave) or performance-graded (PG) asphalt binder specification was developed in the 1990’s to measure binder properties directly related to HMAC performance and included material characterization at low, intermediate, and high temperatures. Direct application of the PG binder specification to binders used in surface treatments is not appropriate due to differences between surface treatments and HMAC in terms of distress types, construction methods, and exposure to environmental conditions. The objective of this study conducted for the Texas Department of Transportation was to develop a performance-based specification system for surface treatment binders that maximizes the use of existing equipment required in the PG system for HMAC binders. This new surface performance grading (SPG) specification assumes appropriate design and construction practices and considers only binder properties after construction. The SPG was developed based on the identification of common distresses and analysis of physical properties at multiple temperatures of surface treatment binders that correlate to these distresses. The final SPG includes limiting values for high and low surface pavement design temperatures. Implementation of the SPG specification is recommended after a field validation experiment.

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A Standardized Procedure for Analysis of the Dynamic Modulus (|E*|) Data to Predict Asphalt Pavement Distresses

Aroon Shenoy

Senior Research Fellow

Turner-Fairbank Highway Research Center

6300 Georgetown Pike

McLean, VA 22101

Tel: [phone]; Fax: [phone]; e-mail: [e-mail]

Pedro Romero

Assistant Professor

Department of Civil and Environmental Engineering

The University of Utah

Salt Lake City, UT 84112

Tel: [phone]; Fax: [phone]; e-mail: [e-mail]

Abstract

The present work provides a standardized procedure by which various asphalt concrete mixtures can be compared and their expected performance can be assessed in a uniform manner using the simple performance test suggested under the National Co-operative Highway Research Program NCHRP 9-19 . Superpave Support and Performance Models Management program. The frequency sweep data generated from the test are available in terms of dynamic modulus |E*| versus frequency at the measurement temperature under different levels of confining stress (0, 20, 30 psi or 0, 2.9, 4.35 mPa). The moduli versus frequency data at different temperatures are unified to form a single curve for each mixture through a normalizing parameter. The temperature at which the normalizing parameter becomes equal to one is designated the specification parameter TS (°C) for assessing mixture performance. Each unified curve is fitted with a constitutive equation from which model parameters are evaluated. The slope B1 in the low frequency region of the unified curve, when normalized with the term (T/ TS), results in a parameter that is related to asphalt pavement distress at high temperature T. It is shown that B1/ TS is related to rut depths measured at different WesTrack, a full-scale test track, sections and the correlation improves with increasing confining stress. There is a good possibility that the slope B2 in the high frequency region of the unified curve may relate to distresses in the intermediate temperature range, such as fatigue cracking. A preliminary check shows that this might be true, but data is too limited to draw firm conclusions.

Keywords: Simple performance test, frequency sweep, standardized procedure, performance-

related specifications, aggregate-asphalt combinations, mixture evaluation

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Determining Air Void Content of Compacted HMA Mixtures

L. K. Crouch, Ph.D., P.E., Professor of Civil Engineering, [e-mail]

Audrey R. Copeland, E.I.T., Graduate Research Assistant, Civil Engineering, [e-mail]

C. Todd Walker, E.I.T., Graduate Research Assistant, Civil Engineering, [e-mail]

Richard A. Maxwell, Civil Engineering Technician, [e-mail]

Daniel A. Badoe, Ph.D., Assistant Professor of Civil Engineering, [e-mail]

H. Wayne Leimer, Ph.D., P.G., Professor of Geosciences, [e-mail]

Tennessee Technological University

Box 5015 TTU

Cookeville, TN 38505

[phone], Fax [phone],

Gregory M. Duncan, Assistant Director of Construction, Tennessee Department of Transportation

Suite 700 J.K. Polk Bldg., 505 Deaderick St., Nashville, TN 37243

[phone], [phone], [e-mail]
William A. Goodwin, P.E. R.L.S., Professor Emeritus of Civil Engineering

Tennessee Technological University, P.O. Box 31515, Knoxville, TN 37930-1515

[phone], Fax [phone], [e-mail]
.

ABSTRACT

The ultimate goal of the project was to develop a new method, or adapt a current method, for determining bulk specific gravity (G_mb) of compacted HMA mixtures with wide applicability. A more reliable G_mb would result in more reliable HMA volumetric properties, specifically percent air voids. Consequently, pavement distress types such as rutting, bleeding, stripping, and age hardening (whose occurrence is related to percent air voids among other factors), could be avoided more often. The project goal was accomplished in three steps. In step 1, a literature review and survey of state departments of transportation revealed thirteen existing G_mb determination techniques. In step 2, a feasibility study was conducted on the seven selected methods to evaluate cost, logistical factors, and preliminary repeatability. In the final step, fifty compacted HMA samples and four aluminum cylinders were used to evaluate the precision and accuracy of the four selected methods. The dimensional analysis (AASHTO T-269) and the parafilm (ASTM D 1188) methods were found to form upper bounds for true sample air voids, while the Saturated Surface Dry method (SSD) (AASHTO T-166) method was found to form a lower bound for true air voids. Although the true air voids can never be determined, for 90 percent of TDOT sample groups tested Instrotek Corelok yielded results in this range between the upper and lower bounds for accurate air void results. All four methods in the precision and accuracy evaluation were found to be capable of producing high precision results.


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Illinois’ Extended Life HMA Pavement Specifications

Eric E. Harm, P.E.

Engineer of Materials and Physical Research

Bureau of Materials and Physical Research

Illinois Department of Transportation

126 East Ash Street

Springfield, Illinois 62704

Phone: [phone]

Fax: [phone]

E-Mail: [e-mail]
David L. Lippert, P.E.

Engineer of Physical Research

Bureau of Materials and Physical Research

Illinois Department of Transportation

126 East Ash Street

Springfield, Illinois 62704

Phone: [phone]

Fax: [phone]

E-Mail: [e-mail]