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USE OF SEMI-CIRCULAR BEND TEST TO CHARACTERIZE FRACTURE PROPERTIES OF ASPHALT CONCRETE WITH VIRGIN AND RECYCLED MATERIALS

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USE OF SEMI-CIRCULAR BEND TEST TO CHARACTERIZE FRACTURE PROPERTIES OF ASPHALT CONCRETE WITH VIRGIN AND RECYCLED MATERIALS

ABSTRACT

Cracking in asphalt pavements is a challenging problem and has been the subject of numerous research studies for decades.  To properly address this problem, suitable tests must be conducted to capture material behavior in cracking, such testing must be accompanied by proper mechanistic and empirical modeling of the material behavior in cracking. For mixture design and material quality control/assurance purposes, there is not a commonly accepted protocol for testing asphalt mixtures for cracking resistance characterization, due to variability of test results, non-uniformity in test specimens, and overall complexities of the tests that prevent them from being adopted for daily uses.    On the other hands, for the tests that are popular for research purposes, the validity and sensitivity of such tests have not been fully witnessed and proven, due to lack of data quantity.     Addressing these problems will help improve mixture design procedures and advance quality control and quality assurance of asphalt mixes, especially when complicated components, such as recycled materials and performance enhancing additives, are commonly incorporated into asphalt concrete nowadays.

 

The overall goal of this research is to characterize the cracking resistance of various types of asphalt concrete mixes via a suitable candidate test.   An additional goal is to provide guidelines for performing balanced mixture design on asphalt concrete with virgin and recycled materials when using such a test.

 

Throughout the research, the selected fracture test, namely the semi-circular bend (SCB) fracture test, was first evaluated by investigating the sensitivity of performance indicators under various test conditions and proposing the most appropriate test conditions using a solid theoretical background.    Then, the test was used to study fracture behavior of a wide range of asphalt paving materials including, but not limited to, various virgin asphalt mixes, crumb rubber modified (CRM) asphalt mixes, asphalt mixes with recycled materials such as reclaimed asphalt pavement (RAP), and recycled asphalt shingles (RAS), together with asphalt mixes with recycling agents.    Not only were these mixtures prepared in a single laboratory, specimens received from different laboratories and plants were also included in the test matrix to reduce bias and to investigate the variation of the performance indicators.    Additionally, a method to conduct the performance-based balanced-design using only the SCB fracture test was explored.  Finally, the effect of long-term aging on fracture behavior of asphalt mixes was investigated, in order to build foundations for performance prediction commonly used in asphalt pavement design procedures.

 

The main contributions of this study are: 1) verification of the sensitivity of the SCB test using asphalt mixtures with controlled variables under the proposed test conditions that are suitable to the commonwealth of Pennsylvania, 2) investigation of the impacts of material variables and conditioning, namely aging process, on fracture behavior of asphalt concretes, 3) exploration of possibility of performing balanced mixture design on asphalt concrete using the SCB test as a stand-alone test.     The SCB fracture test procedure is found to be suitable to qualify asphalt mixes to fulfill different traffic demands and pavement structural conditions.   Reliable mix design and quality assurance of asphalt pavements with complicated rehabilitation histories and sophisticated material compositions can be performed with confidence using such a test.

 

 

TABLE OF CONTENTS

 

LIST OF FIGURES……………………………………………………………………………………………. xi

LIST OF TABLES…………………………………………………………………………………………….. xv

 

 

Chapter 1INTRODUCTION …………………………………………………………………………… 1

1.1           BACKGROUND ………………………………………………………………………………… 1

1.1.1 Problem Statement ……………………………………………………………………………… 2

1.2         RESEARCH OBJECTIVES ………………………………………………………………….. 3

1.3        SCOPE OF WORK AND RESEARCH APPROACH ……………………………….. 3

1.4          RESEARCH CONTRIBUTION ……………………………………………………………. 8

1.5          DISSERTATION ORGANIZATION……………………………………………………… 8

 

Chapter 2 LITERATURE REVIEW ……………………………………………………………….. 10

2.1        FATIGUE BEHAVIOR OF ASPHALT PAVEMENT …………………………….. 10

2.2 FATIGUE CHARACTERIZATION METHODS ………………………………………… 10

2.2.1 Phenomenological Approach ………………………………………………………………. 11

2.2.2 Fracture Mechanics Approach …………………………………………………………….. 11

2.2.3 Viscoelastic Continuum Damage Mechanics (VECD) Approach ………………. 12

2.2.4 Dissipated Energy Methods ………………………………………………………………… 12

2.3 FATIGUE TEST METHODS …………………………………………………………………… 13

2.3.1 Semi-Circular Beam (SCB) Test …………………………………………………………. 13

2.3.2 Push-Pull (Tension-Compression) Fatigue Test ……………………………………… 16

2.3.3 Indirect Tensile (IDT) Test …………………………………………………………………. 17

2.3.4 Other Fatigue/Fracture Tests ………………………………………………………………. 18

2.5 CRUMB RUBBER MODIFIED ASPHALT MIXTURES …………………………….. 20

2.6 FATIGUE PERFORMANCE OF ASPHALT MIXTURES CONTAINING CRM

AND RECYCLED MATERIALS ………………………………………………………………….. 21

2.7 SUMMARY OF LITERATURE REVIEW …………………………………………………. 23

 

Chapter 3 LABORATORY FRACTURE TEST SELECTION ………………………….. 25

3.1 CRITERIA FOR TEST SELECTION ………………………………………………………… 25

3.2 SEMI-CIRCULAR BEND (SCB) FRACTURE TEST ………………………………….. 28

3.2.1 SCB Test Configuration …………………………………………………………………….. 29

3.2.2 Standardized SCB Fracture Test ………………………………………………………….. 31

3.3 SCB FRACTURE TEST PARAMETER CALCULATION …………………………… 33

3.4 SPECIMEN PREPARATION FOR SCB FRACTURE TEST ………………………… 35

 

Chapter 4 THE EFFECT OF TEST TEMPERATURE AND DISPLACEMENT

RATE ON SEMI-CIRCULAR BEND TEST ……………………………………………………. 37

4.1 INTRODUCTION ………………………………………………………………………………….. 37

4.2 OBJECTIVES ……………………………………………………………………………………….. 38

4.3 THEORETICAL BACKGROUND …………………………………………………………… 38

4.3.1 Selection of Test Temperature …………………………………………………………….. 39

4.3.2 Selection of Displacement Rate …………………………………………………………… 41

4.4 MATERIAL AND EXPERIMENTAL PROGRAM …………………………………….. 42

4.4.1 Material Characterization …………………………………………………………………… 42

4.4.2 Specimen Preparation ……………………………………………………………………….. 43

4.4.3 Experimental Program ………………………………………………………………………. 44

4.5 TEST RESULTS AND ANALYSIS ………………………………………………………….. 45

4.5.1 Material Characterization …………………………………………………………………… 45

4.5.2 Effective Temperature Study ………………………………………………………………. 51

4.5.3 Temperature and Displacement Rate Sweep ………………………………………….. 56

4.6 SUMMARY AND RECOMMENDATIONS ………………………………………………. 59 Chapter 5 THE EFFECT OF MATERIAL VARIABLES ON SCB TEST

PERFORMANCE INDICATORS …………………………………………………………………… 61

5.1 INTRODUCTION ………………………………………………………………………………….. 61

5.2 OBJECTIVES ……………………………………………………………………………………….. 62

5.3 MATERIALS AND TEST PROGRAM ……………………………………………………… 63

5.3.1 Materials …………………………………………………………………………………………. 63

5.3.2 Design of Experiment ……………………………………………………………………….. 63

5.3.3 Specimen Preparation ……………………………………………………………………….. 65

5.4 TEST RESULTS ……………………………………………………………………………………. 66

5.4.1 Top vs. Bottom Specimens …………………………………………………………………. 66

5.4.2 Effect of Material Variables ……………………………………………………………….. 69

5.5 SUMMARY AND CONCLUSIONS …………………………………………………………. 84

 

Chapter 6 FRACTIRE PROPERTIES OF ASPHALT MIXTURES WITH CRUMB

RUBBER MODIFIERS …………………………………………………………………………………. 86

6.1 INTRODUCTION AND BACKGROUND …………………………………………………. 86

6.2 OBJECTIVE AND SCOPE OF WORK ……………………………………………………… 88

6.3 SPECIMEN PREPARATION AND EXPERIMENTAL PROGRAM ……………… 88

6.3.1 Material and CRM Preparation ……………………………………………………………. 88

6.3.2 Selection of Study Cases ……………………………………………………………………. 90

6.3.3 Specimen Preparation and SCB Test ……………………………………………………. 91

6.3.4 Linear Amplitude Sweep Test and Dynamic Shear Rheometer Test ………….. 91

6.4 RESULTS AND ANALYSIS …………………………………………………………………… 92

6.4.1 Design of CRM Mixes ………………………………………………………………………. 92

6.4.2 Effect of Crumb Rubber Content and Binder Grade on Properties …………….. 94

6.4.2.1 Initial and Post Peak Stiffness ………………………………………………………….. 94

6.4.2.2 Flexibility Index …………………………………………………………………………….. 95

6.4.3 Effect of Gradation Adjustment in Dense Graded Mixes …………………………. 96

6.4.4 Effect on Other Response Parameters …………………………………………………… 97

6.4.5 Statistical Analysis of Data ………………………………………………………………… 99

6.4.6 The Effect of Gap Gradation versus Dense Gradation …………………………… 101

6.4.7 Fracture Resistance based on Binder Tests ………………………………………….. 102

6.4.7.1 LAS Test Results …………………………………………………………………………. 103

6.4.7.2 DSR Test Results …………………………………………………………………………. 104

6.4.8 Comparison of Fracture Resistance of Binders versus Mixtures ……………… 105

6.5 SUMMARY AND CONCLUSIONS ……………………………………………………….. 106

 

Chapter 7 FRACTURE PROPERTIES OF ASPHALT MIXTURES WITH

ASPHALT RECYCLED MATERIALS …………………………………………………………. 108

7.1 INTRODUCTION ………………………………………………………………………………… 108

7.2 OBJECTIVE………………………………………………………………………………………… 111

7.3 MATERIAL AND TEST PROGRAM ……………………………………………………… 111

7.3.1 Materials and Specimen Preparation ………………………………………………….. 111

7.3.2 Test Program………………………………………………………………………………….. 112

7.4 Results and Analysis ……………………………………………………………………………… 112

7.4.1 Results on Benchmark Mixes ……………………………………………………………. 112

7.5 CONCLUSIONS AND RECOMMENDATIONS ………………………………………. 118

 

Chapter 8 OPTIMIZING REJUVENATOR CONTENT AND USING THE SEMICIRCULAR BEND TEST FOR BALANCED MIX DESIGN ………………………….. 120

8.1 INTRODUCTION AND BACKGROUND ……………………………………………….. 120

8.2 MATERIALS AND TEST PROGRAMS………………………………………………….. 122

8.2.1 Materials ……………………………………………………………………………………….. 122

8.2.2 Hamburg Rutting Test ……………………………………………………………………… 122

8.2.3 Binder Test ……………………………………………………………………………………. 123

8.3 OPTIMIZE REJUVENATOR CONTENTS FOR HIGH RAP MIXES ………….. 125

8.3.1 Design Using SCB and HWTD …………………………………………………………. 125

 

8.4 Comparing SCB Test Parameters to Parameters from Other Performance Tests . 127

8.4.1 High Temperature Indices ………………………………………………………………… 127

8.4.2 Intermediate Temperature Cracking Indices ………………………………………… 131

8.4.3 Discrepancy Verification on Intermediate Temperature Cracking Indices …. 135

8.5 CONCLUSIONS AND RECOMMENDATIONS ………………………………………. 139

 

Chapter 9 EFFECT OF LONG-TERM AGING ON FRACTURE RESISTANCE

OF ASPHALT MIXTURES………………………………………………………………………….. 141

9.1 INTRODUCTION ………………………………………………………………………………… 141

9.2 OBJECTIVE………………………………………………………………………………………… 143

9.3 MATERIALS AND TEST PROGRAM ……………………………………………………. 144

9.3.1 Materials ……………………………………………………………………………………….. 144

9.3.2 Material Processing, Specimen Preparation, and Test Program ……………….. 145

9.4 RESULTS AND ANALYSIS …………………………………………………………………. 145

9.4.1 Comparison of Performance Indices as Affected by Aging Level ……………. 146

9.4.2 Data Quality …………………………………………………………………………………… 151

9.4.3 Effect of Long-Term Aging on Performance Indices in the light of Changes in

Mix Parameters………………………………………………………………………………………. 155

9.4.4 Effect of LTOA on Mixes with Recycled Materials ………………………………. 160

9.5 SUMMARY AND CONCLUSIONS ……………………………………………………….. 166

 

Chapter 10 CONCLUSIONS AND RECOMMENDATIONS…………………………… 168

10.1 CONCLUSIONS ………………………………………………………………………………… 168

10.1.1 The Effect of Test Temperature and Displacement Rate on the Semi-Circular

Bend Test ……………………………………………………………………………………………… 168

10.1.2 The Effect of Material Variable on SCB Test Performance Indicators ……. 169

10.1.3 Fracture Properties of Asphalt Mixtures with Crumb Rubber Modifiers

(CRM) ………………………………………………………………………………………………….. 170

10.1.4      Fracture Properties of Asphalt Mixtures with Recycled Materials ……… 172

10.1.5 Optimize rejuvenator contents for Asphalt Mixtures with Recycled Materials and Using SCB Test for Balanced Mixture Design……………………………………….. 173

10.1.6 Effect of Long-Term Aging on Fracture Resistance of Asphalt Mixtures … 173

10.2 RECOMMENDATIONS ……………………………………………………………………… 175

 

REFERENCES. …………………………………………………………………………………………… 176

Chapter 1 INTRODUCTION

1.1 BACKGROUND

A considerable amount of federal and state funding is spent annually on construction and maintenance of highways to improve functionality, serviceability, and performance of the roads. The road network is an essential and integral part of our daily life. More than 90 percent of road networks in the United States are paved with asphalt paving materials (Copeland, 2011).   Asphalt concrete consists of asphalt binder, graded aggregate, and in some cases other additives and recycled materials.    It is viscoelastic and its behavior is highly dependent on the temperature and loading rate. All components in asphalt mixtures play roles in the overall performance of the mix. Pavements in poor condition result in poor ride quality and potential safety concerns.

 

There are three major distresses in asphalt pavement: permanent deformation (rutting), thermal cracking, and fatigue cracking. All could be reduced through proper mix design (material selection and combination), structural design (thickness selection), and highquality construction.    Fatigue cracking, or in a broader sense, intermediate temperature cracking, which is the focus of this research, refers to independent or interconnected cracks, varying in size, that develop in the pavement structure.   It is a result of exposure of asphalt paving materials to repeated traffic or thermal loading after they have been oxidatively aged severely.    Propagation of fatigue cracks in asphalt pavement will eventually result in raveling (i.e., loss of fine aggregate), and will allow moisture to infiltrate into the pavement system, deteriorating the pavement structure and reducing its serviceability.   Despite the development of many experimental and analytical techniques to tackle the fatigue cracking, this type of distress continues to be a challenging problem requiring more reliable testing and analytical systems, especially during the design and construction stages.

 

Performance of asphalt pavements with respect to intermediate temperature cracking has been investigated through collection of field performance data and simulation of traffic loads using accelerated loading of full or scaled test tracks. Such procedures are often timeconsuming and expensive.    Simpler and less costly approaches for characterization of

1

asphalt mix resistance to intermediate temperature cracking include the use of bench scale laboratory tests.   Such tests are inferior to full-scale or model-scale accelerated loading tests with respect to simulating loading conditions that resemble actual field conditions more closely. However, they do provide the advantage of a faster and more economical approach, better control of test parameters, and the ability to capture material engineering properties more accurately.

 

Laboratory fracture tests can be classified into two major categories: monotonic load tests and cyclic load tests. In monotonic load tests, as the name implies, the load is applied on the test specimen in one run at a constant deformation rate. The load is typically increased until failure of the specimen is observed and even continued beyond the failure point. The most common monotonic tests used in asphalt mixture studies are indirect tensile test (IDT) and semi-circular beam (SCB) test.     In cyclic load tests, repeated loading cycles (sometimes as many as several million) are applied at either stress control or strain amplitude control modes. Load repetition is continued either until certain failure criteria are met or the total failure of the specimen has occurred. The most common cyclic fatigue tests are four-point bending beam (4PBB) or flexural beam test, uniaxial push-pull (compression-tension) fatigue test, and cyclic IDT test.

 

Although some of these test methods have been used by researchers for decades, for asphalt mixture design or material quality control/assurance purposes, however, there is no commonly accepted protocol for testing asphalt mixtures for cracking resistance characterization yet, due to variability of test results, nonuniformity in the test methods, and overall complexity and sensitivity, or lack of, of the tests.

 

1.1.1 Problem Statement

Intermediate temperature cracking in asphalt paving materials is a challenging problem requiring suitable testing and analytical systems. No mechanical test protocol has been adopted for routine mixture design and material quality control/quality assurance purposes at this point, although engineers have been struggling to characterize the fracture behavior of increasingly sophisticated asphalt concretes.    A simple, efficient, yet sensitive fracture test is needed to aid engineers for decision making. Addressing these problems will help improving mixture design procedures and advance quality control and quality assurance of asphalt mixes during construction.

 

Adding the complexity to the asphalt concrete is the inclusion of recycled materials, namely crumb rubber modifiers (CRM), reclaimed asphalt pavement (RAP), and recycled asphalt shingles (RAS). Scrap vehicle tires are a growing environmental problem in the United States. Even though use of CRM, the end product of scrap vehicle tires, in asphalt binder has been researched extensively, there is insufficient information on the effect of crumb rubber in asphalt concrete cracking resistance under a performance-based rational mix design approach.   A similar, though lesser, concern exists with the use of other recycled materials such as RAP and RAS. Investigating and understanding the behavior of asphalt mixtures in terms of cracking resistance when recycled materials are used, and incorporating the results in mix design, could lead to better utilization of recycled materials, resulting in significant cost savings and environmental benefits.

 

1.2 RESEARCH OBJECTIVES

The overall goal of this research was to characterize the intermediate temperature fracture properties of asphalt concretes with virgin and recycled materials via a suitable candidate fracture tests.    Additional goals were to provide guidelines for optimizing the rejuvenator dosage for asphalt mixes with recycled materials, and explore possibility of using a single test for balanced mix design for asphalt concrete with virgin and recycled materials.

 

1.3 SCOPE OF WORK AND RESEARCH APPROACH

The research had a series of well-defined tasks to cover gathering background information, material procurement, specimen preparation, testing, analysis, and finally development of design guidelines.   The materials investigated in the research consisted of typical asphalt paving materials and recycled materials used in the Commonwealth of Pennsylvania.

 

Throughout the research, the selected fracture test, namely the semi-circular bend (SCB) fracture test, was first evaluated by investigating the sensitivity of performance indicators under various test conditions and proposing the most appropriate test conditions using a solid theoretical background.    Then, the test was used to study fracture behavior of a wide variety of asphalt paving materials including, but not limited to, various virgin asphalt mixes, crumb rubber modified (CRM) asphalt mixes, asphalt mixes with recycled materials such as reclaimed asphalt pavement (RAP), and recycled asphalt shingles (RAS), together with asphalt mixes with recycling agents.    Not only were these mixtures prepared in a solo laboratory, specimens received from different laboratories and plants were also included in the test matrix to reduce bias and to investigate the variation of the performance indicators.    Additionally, a method to conduct the performance-based balanced-design method using only the SCB fracture test was explored.  Finally, the effect of long-term aging on fracture behavior of asphalt mixes was investigated, in order to build foundations for performance prediction commonly used in asphalt pavement design procedures.

 

To address the objectives of the research, a three-phase research approach with seven tasks is proposed and shown in Figure 1-1. Details of each task are presented next.

 

 

Figure 1-1. Flow chart of the overall research framework.

Literature Review and Theoretical Background

A comprehensive literature review was conducted to gather and summarize information regarding fatigue and intermediate temperature fracture behavior of asphalt mixtures in general, characterization methods and quantifying parameters on asphalt mixtures, and fatigue and intermediate temperature cracking behavior of asphalt mixtures with crumb rubber modifiers and recycled asphaltic materials.

 

Task 1. Select Fracture Test Method

The semi-circular bend (SCB) fracture test was selected as the most suitable laboratory test for routine mix design and quality control of asphalt paving materials. The decision was based on criteria proposed by previous studies.    Different approaches to perform SCB test were introduced next, followed by the details on the test configuration and the final test procedures used throughout this research. This task also included information such as the unique method proposed by the author to calculate performance indicators.

 

Task 2. Revise and Verify the Selected Test Method

The effect of displacement rate and temperature on the sensitivity of the SCB fracture test was investigated.   Numerous asphalt mixes with controlled variables were tested with SCB fracture tests under a range of displacement rates and test temperatures to investigate how performance indicators such as fracture energy, flexibility index, and peak load respond to changing test conditions, and whether these indicators remain sensitive under different test conditions.    The temperature and displacement rate sweep tests were also performed on a selected mix to study the fundamental characteristics of performance indicators. Finally, a SCB fracture test condition that is suitable for Pennsylvania was identified.

 

Task 3. Evaluate Fracture Behavior of Virgin Mixes

For this task, efforts were undertaken to investigate the impact of material variables, e.g., air void, binder content, and binder stiffness, on performance indicators of the SCB fracture test using virgin materials.   The fractional factorial test matrix was designed statistically to account for the influence of all material variables. The responses of performance indicators under different material variables were analyzed via statistical approaches.   A simple regression expression was proposed to predict performance indicators using the data generated in this study. A general guideline for improving asphalt mixtures’ resistance to cracking and the limitation of using flexibility index is proposed as a result of this research.

 

Task 4. Evaluate Fracture Behavior of Asphalt Mixes with Crumb Rubber Modified (CRM)

This task studied the fracture properties of crumb rubber modified (CRM) asphalt mixes using the SCB fracture test.    The focuses were primarily on the effect of gradation, CRM content, virgin binder stiffness, and binder contents. Performance indicators were also compared with binder fatigue test results.

 

Task 5. Evaluate Fracture Behavior of Asphalt Mixes with Recycled Materials:

Effect of Reclaimed Asphalt Pavement (RAP), and Recycled Asphalt Shingles (RAS)

This task examined the fracture properties of asphalt mixtures with recycled materials such as reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) using the SCB fracture test.    For this part, the focus was on the types and contents of recycled materials, comparison to virgin mixtures, and the effect of dosage and types of recycling agents, i.e., rejuvenators.

 

Task 6. Rejuvenator Optimization for Asphalt Mixes with Recycled Materials and Dual Purpose Usage of the SCB Test

The task aimed to propose using a stand-alone fracture test (SCB fracture test), together with two performance indicators, i.e., flexibility index and peak load, to optimize rejuvenator dosages for asphalt mixes with recycled materials.   Performance indicators obtained from the mixture fracture test, i.e., the SCB fracture test, were compared with performance indicators measured from binder performance tests.   Peak load obtained from the SCB test was also compared with rut depth measured from the Hamburg wheel tracking device to verify the proposition of correlating rut depth measurement from the wheel tracking test with peak load of the SCB test for the purpose of balanced mix design.

 

Task 7. Investigate the Effect of Long-Term Aging on Fracture Properties of Asphalt Mixes

The SCB fracture test was performed on various asphalt mixes prepared by different laboratories. The effect of long-term aging (LTA) on fracture performance indicators was investigated by comparing performance indicators before and after the mixes were exposed to LTA. The responses of material variables and the effect of recycled materials under LTA were also evaluated.

 

1.4 RESEARCH CONTRIBUTION

The main contributions of this study are: 1) verification of the sensitivity of the SCB test using asphalt mixtures with controlled variables under the proposed test conditions that are suitable to the commonwealth of Pennsylvania, 2) investigation of the impacts of material variables and conditioning, namely aging process, on fracture behavior of asphalt concretes, 3) exploration of possibility of performing balanced mixture design on asphalt concrete using the SCB test as a sole test.

 

The SCB fracture test procedure is found to be suitable to qualify asphalt mixes to fulfill different traffic demands and pavement structural conditions.    Reliable mix design and quality assurance of asphalt pavements with complicated rehabilitation histories and sophisticated material compositions can be performed with confidence using such a test and the material performance database generated through this research.

 

1.5 DISSERTATION ORGANIZATION

Chapter two summarizes the literature review. Chapter three analyzes the reasons for selecting the SCB fracture test and details the test procedure, alongside the unique method for parameter calculation.   Chapter four discusses the effect of displacement rate and temperature on the sensitivity of the SCB fracture test.    Chapter five shows how material variables affect performance indicators of the SCB fracture test using virgin materials.

Chapter six presents the fracture behavior of crumb rubber modified (CRM) asphalt mixes. Chapter seven presents fracture behavior of asphalt mixes with recycled materials and recycling agents.    Chapter eight discusses how to optimize rejuvenator dosages on asphalt mixes with recycled materials and verification of using the SCB test as the sole test to fulfill the goal of balanced mix design using both binder performance tests and other mix performance tests.  Chapter nine presents discussions on the effect of long-term aging (LTA) on fracture properties of asphalt mixes.   Finally, chapter ten summarizes the most important observations and conclusions from each chapter and proposed recommendations for future study.

USE OF SEMI-CIRCULAR BEND TEST TO CHARACTERIZE FRACTURE PROPERTIES OF ASPHALT CONCRETE WITH VIRGIN AND RECYCLED MATERIALS

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