KLK581 Development and Evaluation of Performance Measures to Augment Asphalt Mix Design in Idaho
ITD Research Project 261; Task Order Number UI-17-01
Principal Investigators
- Emad Kassem
- Fouad Bayomy
ITD Project Manager
- Mike Santi
FHWA Project Advisor
- Kyle Holman
Student Researchers
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Research Problem Statement
Currently, the Superpave volumetric mix design is conducted without performance criteria to evaluate the mix resistance to cracking (fatigue and low temperature thermal), rutting and moisture damage. Asphalt pavements in Idaho and in the northwest in general, experience a wide range of temperatures that lead to rutting at high temperatures and thermal cracking at low temperatures. Mix design based on volumetrics only may satisfy the Superpave specifications but will greatly affect the mix performance under these wide ranges of climactic conditions, Rutting and cracking have been observed in pavements that were designed using the Superpave method. With the use of recycled asphalt pavement (RAP) and recycled asphalt shingles (RAS), asphalt mixes tend to get stiffer and would crack prematurely if not properly designed. Previous research in Idaho (RP 213) has recommended an option of a cracking performance for RAP mixes. Some states (e.g. Washington, Louisiana, Texas) have already developed and implemented performance measures to quantify the resistance of asphalt mixtures to rutting, cracking, and moisture damage before they can be used in pavement construction. Therefore, there is a need to develop and evaluate performance measures for asphalt mixtures with and without RAP/RAS in Idaho. The proposed performance measures will augment the current Superpave mix design method by setting threshold values for performance acceptance.
Project Objectives
The main objective of this proposed research is to evaluate and recommend candidate performance tests to evaluate the resistance of asphalt mixtures to cracking (fatigue and thermal), rutting and moisture damage. In addition, the research team will develop specification limits for these tests to be included in the asphalt mix design in Idaho. Asphalt mixtures prepared with and without RAP/RAS will be evaluated.
Project Tasks
The goal of this project will be achieved by executing a number of tasks. Firstly, the research team will conduct a literature search to review and document the current performance tests used by various states to evaluate the resistance of asphalt mixtures to rutting, cracking, and moisture damage. The research will identify the most promising tests to evaluate the above mentioned distresses based on the reported performance in the literature. Secondly, the research team will identify test sections in Idaho with different resistance to rutting, cracking, and moisture damage. Thirdly, the team, with the help of ITD, will recover field cores as well as laboratory-prepared samples. Fifthly, the team will compare the laboratory results to field performance and identify the tests that provide close performance to field observations. Sixthly, the team will develop performance specifications for each test selected to evaluate various distresses (rutting, cracking, moisture damage). Finally, the team will prepare a final report with the proposed performance tests and their specifications in ITD formats. The project tasks are outlined below.
Task 1: Literature Review
Under this task, the team will conduct a thorough review to document the current tests used by various transportation agencies to review cracking, rutting, and moisture damage of asphalt mixtures. In addition, the team will review the specification limits set by different states for these tests. The literature review will include, but not be limited to:
- Cracking tests: several tests are currently used to evaluate the resistance to asphalt mixtures to cracking including semi-circular bending test (SCB), Texas overlay, bending beam fatigue test, direct tension cyclic fatigue test, indirect tension (IDT), and asphalt pavement analyzer (APA) Junior (Jr) fatigue test.
- Rutting tests: various tests are used to asses the rutting of asphalt mixtures. These tests include Hamburg wheel tracking, APA and APA Jr, and dynamic repeated load tests.
- Moisture damage tests: one of the early methods used to evaluate the resistance of asphalt mixtures to moisture damage was developed by Dr. Robert Lottman at the university of Idaho. This test is used by pavement community worldwide with some modifications. Other tests used to evaluate moisture susceptibility of asphalt mixture include Hamburg wet test and APA Jr.
The outcome of the literature review will be identifying the most promising laboratory tests that will be conducted in Task 4 to evaluate the resistance of asphalt mixes to the above mentioned distresses. Researchers will work closely with ITD's project Technical Advisory Committee to select performance tests to be reviewed. many factors shall be considered when selecting the performance tests including their applicability to simulate field performance, simplicity of the test, applicability to Idaho conditions, availability of the equipment at ITD laboratories, and being cost- and time-effective.
Task 2: Identify and select pavement sites for evaluation
The research team will work with ITD district material engineers to identify and select candidate pavement sites across Idaho for evaluation. Several criteria will be considered when selecting the test sections. These criteria include:
- Distress type and severity: pavement test sections that manifest various distresses (cracking {fatigue and thermal], rutting, moisture damage) and other sections with good performance and without major distresses will be identified.
- Mixture design: asphalt pavements with different mixture design shall be included. The number of test sections at various mix design shall be decided by the research team and ITD Technical Advisory Committee and based on the frequent use of a given mix design on highways.
- Construction materials: asphalt pavements made of different binder grades and sources as well as aggregates shall be considered.
- Pavement structure and support: asphalt pavements with different structural design (layer thickness) as well as base and subgrade strength shall be considered. Pavement distresses are not only related to poor asphalt courses but in many cases they are related to poor (insufficient) structural support.
- Environmental conditions: the test sections shall be distributed across the state and sites from all six districts will be included in this study. The environmental conditions have a great impact on the performance of asphalt mixtures and the type and degree of severity of various distresses.
- Traffic level: interstate highways, US highways, and state highways subjected to different traffic levels shall be considered.
- Service life: asphalt pavements sites with different ages shall be included. Pavement sites with more than five years in service are recommended so that pavements had enough time to develop distresses.
Task 3: Conduct field performance evaluation and collect cores and virgin materials
Under this task, the research team with help from ITD will obtain field cores and collect virgin materials (binders and aggregates) from the selected sites under Task 2. Field Cores will be extracted from the wheel path and shoulder. In case there is no shoulder, field cores between wheel path will be obtained. It is expected that some field cores collected from the wheel path will be distressed compared to cores from the shoulder or between wheel path while no or less traffic applied, respectively. In addition, the research team will obtain the mix design of the selected sites, The team will document the distress type and its severity as well as obtain the mix design of the selected sites. The team will document the distress type and its severity as well as possible causes for such distress. The results of field performance evaluation will be compared to laboratory performance evaluation under task 5. The following information will be obtained for selected sites:
- Project Location
- Date of construction
- Pavement structure (layer thickness) and material properties
- Traffic volume
- Historical performance data such as rutting and cracking
- Maintenance and rehabilitation history
- Climate information
- Ground water table level
Task 4: Conduct laboratory performance tests
Laboratory asphalt mixture test samples will be prepared using the virgin materials in accordance with the mixture design collected in Task 3. Part of laboratory test samples will be subjected to long-term aging to simulate the conditions of asphalt mixtures in the pavement sites. Studies at Texas A&M showed that placing asphalt mixture test samples in an environmental chamber at 60°C for a few months (about three months) simulate several years of asphalt pavement aging tin the field. Previous studies showed that fatigue cracking and moisture damage may increase as the asphalt mixture ages in the field. A comprehensive laboratory testing program will be conducted on both laboratory test samples and recovered field cores. The selected tests under Task 1 will be conducted to evaluate the resistance of asphalt mixtures to cracking (fatigue and thermal), permanent deformation or rutting, and moisture damage. At least three different tests will be evaluated to study the resistance of asphalt mixtures to various distress modes (fatigue and thermal cracking, rutting, and moisture damage). At this time and based on the limited literature review performed by the research team during the course of the preparation of this task order, the following tests are thought:
- Cracking tests: direct tension cyclic fatigue test, semi-circular bend (SCB), indirect tension (IDT) may be conducted to evaluate the resistance of asphalt mixture to fatigue and thermal cracking.
- Rutting tests: Hamburg wheel tracking or AOA Jr, dynamic repeated load tests, and flow number and flow time test may be conducted to evaluate the resistance of asphalt mixtures to rutting.
- Moisture damage tests: modified Lottman test, IDT, and direct tension cyclic, and Hamburg wheel tracking or APA Jr in wet conditions may be used to study the moisture susceptibility test samples.
Furthermore, under Task 4, the research team is planning to conduct inter-laboratory experiments to compare the repeatability and variability of different performance tests conducted at the university of Idaho and other ITD laboratories. It is envisioned that the inter-laboratory experiments will include performance tests (rutting, cracking, and moisture damage) for three different mixtures. At least three replicates will be evaluated in each test.
Task 5: Comprehensive evaluation of laboratory and field performance data
The results of the laboratory testing program conducted under Task 4 will be analyzed and compared to the performance evaluation in the field. Statistical analysis methods will be used to analyze the test results and evaluate the significance of the effect of different variables (e.g. traffic level, aggregate gradation, aggregate type, binder grade, etc.) on the performance test results. The expected outcome of this task shall enable us to:
- Evaluate the applicability of various performance tests to asses the resistance of asphalt mixtures to rutting, cracking, and moisture damage, in addition to compare the results to field observations. The evolution of various test methods shall cover the simplicity of the test, availability of test devices in a typical asphalt laboratory, need for skilled staff, and required time and cost of the test.
- Identify the most promising and applicable test(s) that provide close performance prediction to field observation for each pavement distresses (rutting, cracking, and moisture damage).
Task 6: Develop performance test specifications
Based on the findings of Task 5, the research team will develop performance specifications for each test selected to evaluate the resistance of asphalt mixtures to cracking, rutting, and moisture damage. These limits or specifications shall be augmented to the mix design used by ITD. The proposed test method(s) will be prepared in ITD standard test formats. In addition, the researchers will organize a workshop to demonstrate and train ITD personnel on the proposed test methods and seek feedback from ITD engineers.
Task 7: Prepare the final report
The research team will prepare a comprehensive final report at the end of the study to document the research methodology, present the results and analysis, summarize the findings, and provide recommendations and propose plans for future studies and implementation. In addition, the final report shall include the proposed test methods to evaluate the performance of asphalt mixtures in ITD formats. The report will be edited by a professional editor and reviewed by an external expert.
Project Communication Schedule
The research team will prepare a monthly progress report on ITD form. There will be frequent - at least quarterly- meetings with the project technical advisory committee from ITD to discuss progress. Depending on time and people availability, these meetings could be held in person, face-to-face or via video conferencing. As a minimum, the research team will have three face-to-face meetings; kick-off meeting, progress meeting (after 1 year), close-out meeting (toward the end of the project).
Needs and Requirements
Like other projects with ITD, this is a cooperative effort between ITD and U of I. The research team will seek help and support of ITD to execute the project tasks. Specific needs are:
- Identification and selection of field test sections as per Task 2
- Procuring materials (aggregate and binders) and field cores from the selected test sections as per Task 3
- Providing performance data from TAMS database and/or other records that enable the team to asses performance of the selected pavement sections
- Conducting limited inter-laboratory experiments to check the repeatability and consistency of selected performance tests as per Task 4.
Required Outputs/Deliverables
Required project output will be as follows:
- Identification and selection of field test sections as per Task 2
- Proposed test methods to evaluate mix resistance to cracking, rutting, and moisture damage
- Performance indicators (threshold limits) for the proposed methods
- Comprehensive final report
There are seven deliverables as outlined below:
Deliverable No. 1: Literature review
The research team will provide a summary of the literature review to document the current tests used to evaluate cracking, rutting, and moisture damage of asphalt mixtures. In addition, the team will review the specification limits set by different states for these tests. The outcome of the literature review will be selecting the most promising laboratory tests that will be conducted in Task 4 to evaluate the resistance of asphalt mixtures to the above mentioned distresses.
Deliverable No. 2: Test section selection
A technical memorandum will summarize the candidate test sections selected by the research team and ITD for evaluation in this study. Several criteria will be considered when selecting the test sections including distress type and severity, mixture design, construction materials, pavement structure and support, environmental conditions, traffic level, service life, etc.
Deliverable No. 3: Field performance evaluation and laboratory experiment design
A technical memorandum shall provide preliminary results of field performance evaluation of selected test sections, in addition to the design of laboratory testing program including performance tests for rutting, cracking and moisture damage, testing temperature, various asphalt mixtures with and without RAP/RAS, field cores, number of replicates, etc.
Deliverable No. 4: Preliminary laboratory test results
A technical memorandum shall report the preliminary test results of various laboratory performance tests conducted under Task 4 and the correlations with field performance.
Deliverable No. 5: Final results of the laboratory testing program
A technical memorandum will report the final results of the laboratory testing program and the analysis of the laboratory and field performance data.
Deliverable No. 6: Development of performance measures
A technical memorandum will report the proposed performance tests to evaluate the resistance of asphalt mixtures to cracking, rutting, and moisture damage and the proposed specifications to screen asphalt mixtures with good and poor performance. The suggested limits or specifications shall be augmented to the mix design used by ITD.
Deliverable No. 7: Draft report
The draft report shall document the research methodology, present the results and analysis, summarize the findings, and provide recommendations and propose plans for future studies and implementation. in addition, the report shall include the proposed test methods to evaluate the performance of asphalt mixtures in ITD formats.
Deliverable No. 8: Final report
The final report shall address the ITD comments on the draft report as well as comments from the external reviewer.
Implementation
The outcomes can be included or amended to the current mix design used in Idaho to ensure adequate resistance to cracking, rutting, and moisture damage. The ITD engineers shall be able to use the proposed test methods to screen poor mixtures that may have some performance issues in the field at early stage (mix design). The Project Sponsor, Project Manager, and TAC members will meet with the researchers to discuss study recommendations as part of the report review process. The researchers will assist the ITD Project Sponsor, Project Manager, and Technical Advisory Committee in developing a plan to implement study recommendations requiring action, a schedule for implementation activities, and the individuals responsible for specific implementation steps.
Expected Outcomes/Savings to ITD
Development of performance threshold limits based on the conditions in the state of Idaho will enable ITD engineers to design asphalt mixture with adequate resistance to cracking, rutting, and moisture damage.
- Proper mixture design will lead to asphalt pavements with improved performance
- Training ITD engineers to conduct and analyze the results of the proposed performance tests
- Improving the durability and longevity of asphalt pavements would significantly reduce the maintenance and rehabilitation expenses spent on repairing asphalt pavements that fail prematurely, which directly increases mobility and safety.
Monthly Progress Reports (ITD 771) and Task Progress Charts
Project status
Active
Draft report
Due November 2018
Final report
Due January 2018