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  • , Technical Report Documentation Page

    1. Report Number 2. Government Accession No. 3. Recipient's Catalog No.

    FHWA/TX-95/1332-2F 4. Title and Subtitle 5. Report Date

    November 1994 SHORT-TERM GUIDELINES TO IMPROVE CRUMB RUBBER MODIFIED ASPHALT CONCRETE PAVEMENTS

    6. Performing Organization Code

    7. Author(s) 8. Performing Organization Report No.

    Sekhar Rebala, Cindy K. Estakhri, Mohan Gownder and Dallas Little

    Research Report 1332-2F

    9. Performing Organization Name and Address

    Texas Transportation Institute The Texas A&M University System College Station, Texas 77843-3135 12. Sponsoring Agency Name and Address

    Texas Department of Transportation Research and Technology Transfer Office P. 0. Box 5080 Austin, Texas 78763-5080 15. Supplementary Notes

    10. Work Unit No.

    11. Contract or Grant No.

    Study No. 0-1332 13. Type of Report and Period Covered

    Final: September 1992-August 1994 14. Sponsoring Agency Code

    Research performed in cooperation with the Texas Department of Transportation and the U.S. Department of Transportation, Federal Highway Administration. Research Study Title: Short-Term Guidelines to Improve Asphalt-Rubber Pavements

    16. Abstract

    The objective of this study was to optimize the performance of crumb rubber modified (CRM) asphalt-concrete pavements through the development of materials and construction specifications, mixture design and testing procedures, binder testing procedures, and quality control and construction guidelines. These objectives were accomplished through an extensive laboratory investigation and somewhat limited field investigation.

    This report presents guidelines, draft material specifications, and test protocol regarding the use of crumb rubber modifier in asphalt concrete pavements. Researchers found that CRM has the potential to improve the fatigue and thermal cracking performance of asphalt concrete pavements. Performance of crumb rubber modified asphalt concrete pavements is predicted using the Texas Flexible Pavement System (TFPS). Pavements were analyzed under a variety of climatic and structural conditions.

    Although state DOTs must comply with the existing legislative requirements, tire rubber, as any additive, should be used whenever possible to address a given mixture deficiency or expected deficiency in a given situation.

    17. Key Words

    Crumb Rubber Modifier, CRM, Recycled Tire Rubber, Asphalt Rubber, Modified Binders, Modified Asphalt Concrete

    18. Distribution Statement

    No restrictions. This document is available to the public through NTIS: National Technical Information Service 5285 Port Royal Road Springfield, Virginia 22161.

    19. Security Classif.( of this report)

    Unclassified 20. Security Classif.(of this page) 21. No. of Pages 22. Price

    Unclassified 205

    Form DOT F 1700.7 (8-72) Reproduction of completed page authorized

  • SHORT-TERM GUIDELINES TO IMPROVE CRUMB RUBBER MODIFIED ASPHALT CONCRETE PAVEMENTS

    by

    Sekhar Rebala Research Assistant

    Texas Transportation Institute

    Cindy K. Estakhri, P.E. Assistant Research Engineer

    Texas Transportation Institute

    Mohan Gownder Research Assistant

    Texas Transportation Institute

    Dallas N. Little Research Engineer

    Texas Transportation Institute

    Research Report 1332-2F Research Study Number 0-1332

    Research Study Title: Short-Term Guidelines to Improve Asphalt-Rubber Pavements

    Sponsored by the Texas Department of Transportation

    In Cooperation with U.S. Department of Transportation

    Federal Highway Administration

    November 1994

    TEXAS TRANSPORTATION INSTITUTE The Texas A&M University System College Station, Texas 77843-3135

  • IMPLEMENTATION STATEMENT

    The goal of this study is to provide short-term guidelines to improve the performance

    of hot mix asphalt pavements which have been modified with crumb rubber. This report

    documents partial completion of this goal. Mixture design procedures, test procedures, and

    material properties of CRM binders and mixtures have been evaluated.

    The findings of this study indicate that crumb rubber can be incorporated into hot-

    mix asphalt concrete without having a detrimental effect on pavement performance (when

    the mixture is designed and placed properly). The findings also indicate that crumb-rubber

    modified binders may be designed to produce asphalt mixtures that inhibit cracking.

    Implementation of these research results will aid the Texas Department of

    Transportation, as well as other state DOTs, in meeting the requirements of the Intermodal

    Surface Transportation Efficiency Act of 1991 (ISTEA). ISTEA provides for a minimum

    utilization requirement for asphalt pavement containing crumb rubber modifier as a

    percentage of the total tons of asphalt laid in such state. Guidelines, materials specifications

    and test protocol are provided to aid in implementation.

    v

  • DISCLAIMER

    The contents of this report reflect the views of the authors who are responsible for

    the facts and the accuracy of the data presented herein. The contents do not necessarily

    reflect the official view or policies of the Texas Department of Transportation (TxDOT) or

    the Federal Highway Administration (FHWA). This report does not constitute a standard,

    specification, or regulation, nor is it intended for construction, bidding, or permit purposes.

    vu

  • TABLE OF CONTENTS

    Page

    List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xii

    List of Tables ...................................................... xiv

    Summary ......................................................... xv

    Chapter 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

    Chapter 2 Mixture Performance Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

    2.1 Rutting ................................................. 5

    Tex 231-F TxDOT Static Creep Test ........................... 6

    2.2 Fatigue Cracking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

    AAMAS Criteria ......................................... 20

    SHRP Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

    2.3 Thermal Cracking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

    Thermal Cracking - Strain Energy Criteria . . . . . . . . . . . . . . . . . . . . . . 33

    Chapter 3 Performance Evaluation of CRM Mixtures Using TFPS ............ 35

    3.1 Performance Evaluation ................................... 36

    Design Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

    Traffic ................................................. 37

    Material Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

    3.2 Discussion of Results ...................................... 39

    Analysis of Structure I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

    Analysis of Structure II . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

    Analysis of Structure III . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

    Analysis of Structure IV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

    Analysis of Structure V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 7

    3.3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

    1X

  • Chapter 4

    4.1

    4.2

    4.3

    4.4

    Chapter 5

    5.1

    5.2

    5.3

    Chapter 6

    6.1

    TABLE OF CONTENTS (continued)

    Page

    Use of Dynamic Shear Rheometer for Measurement

    of CRM Binder Viscosity ................................... 51

    Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

    Theory ................................................ 53

    Materials and Experimentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

    Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

    Field Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

    Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

    Short-Term Pavement Performance ........................... 71

    Laboratory Evaluation of Abilene and Lufkin

    Field Mixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

    Draft Materials Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

    Crumb Rubber Modified Mixture Evaluation . . . . . . . . . . . . . . . . . . . . 77

    Unconfined Creep Test .................................... 78

    6.2 Crumb Rubber Modified Binder Evaluation . . . . . . . . . . . . . . . . . . . . . 79

    Chapter 7

    Chapter 8

    C

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