KLK568 Evaluation of Fiber-Reinforced Asphalt Pavements — Phase 1: Laboratory Study
ITD Research Project 237; Task Order Number UI-14-02
Principal Investigators:
- Fouad Bayomy
ITD Project Manager
- Dan Harelson
FHWA Project Advisor:
- Kyle Holman
- Subaward
- Haifang Wen, WSU
Research Problem Statement:
ITD is planning to use three different reinforcing fibers for a 3.22 mile long pavement project on US-30 east of Montpelier City in Southeast Idaho (ITD Key No. 13104). The project will involve building four sections; three with fibers and one control section. There will be four different HMA mixes (three with fibers and one as a control). ITD plans to use this project as a pilot study to evaluate the effectiveness of using fibers in HMA to improve the pavement resistance to cracking and rutting. There are three vendors who will supply the three types of fibers. Forta Co., Nycon Corporation and Surface-Tech, Inc. There is a need to evaluate the proposed mixes in the lab. Lab evaluation is to assess and compare the performance of these mixes in the lab, and to establish mix properties data that shall be needed for performance evaluation using AASHTOWare ME Pavement Design software.
Project Objectives:
The overall goal of the ITD project at Montpelier is to determine the effectiveness of using fibers in HMA to improve cracking and rutting resistance. The scope of this lab-based phase of ITD project addresses the evaluation and comparison of the proposed mixes based on lab tests. The first phase will involve collecting, analyzing and reporting on laboratory and construction data. ITD plans to follow up with a 2nd phase which will involve analyzing and reporting on performance data collected in the years subsequent to construction and that will be addressed separately.
Project Tasks:
Task 1: Literature Review on Fibers in HMA:
A study will be conducted to learn the different technologies used in using fibers in HMA and their effect on asphalt pavement performance.
Task 2: In-Depth Study of the proposed types of Fibers in this Project:
More in-depth study will be focused on the three types of fibers proposed for this project. This will include interviewing the three vendors and learning what they propose to do to install their test sections. This will also include procuring samples of fibers used and collecting relevant literature to document the properties of these fibers and the technologies adopted to include them in HMA.
Task 3: Mix Design, Construction of Test Sections and Material Procurement:
The mix design of the control and the three fiber sections shall be developed by the contractor and shall be provided to the U of I team. U of I team will study the mix design and provide any feedback as needed by the contractors and vendors of the fibers. The construction of the test section will essentially be supervised by ITD – D5 engineers. To the extent of the availability, U of I team will try to attend the construction especially on the days of laying down the fiber reinforced sections. ITD will coordinate procurement of HMA materials from field mixes as being constructed. Collection of field samples will be in accordance with ITD standard procedures. From each mix, ITD shall collect about 1000 lbs of plant mix. It is recommended that mix boxes be limited to no more than 50-70 lbs per box for easy handling. It is expected about 20 boxes from each mix will be collected. U of I and WSU teams will participate to gather and document the mix design and material properties of the test sections.
While there is no urgent need to have raw materials, it is highly encouraged that ITD keep sufficient amount of raw materials of aggregates, binders and fibers as well as samples of base, sub-base and subgrade materials for later characterization. This information would be needed as design inputs when running the AASHTOWare ME Design software for calibration purposes in the future.
Task 4: Lab Testing and Data Analysis:
This task will be conducted cooperatively among U of , WSU and ITD. U of I team will oversee the whole testing plan.
As listed below, U of I will perform tests a, b and c. WSU will perform tests d, e, f, and g. ITD will perform test h (APA).
- Gyratory Stability: All mixes will be evaluated at U of I lab using the Superpave Gyratory Compactor to determine the Gyratory Stability of all mixes, and determine whether the addition of fiber has any significant effect on the GS value of the mix in comparison with the control mix.
- Dynamic Testing: To determine, for each mix, the dynamic modulus at different temperatures and develop the E* - Master Curve. The test will be conducted in the AMPT machine at U of I. This information is essentially needed for the input in the ME Design software, which is performed under task 6. The test will be conducted in accordance to AASHTO TP62. In addition, Dynamic modulus in indirect tensile (IDT) testing mode will be conducted at different temperatures (-20, -10, 0, 10, 20, and 30ºC) and different frequencies (0.1, 1, 5, 10, 20 Hz). The mixtures will be short-term aged in accordance with AASHTO R30. Three replicates will be used for each of four mixes. The air void of the specimens will be 4±0.5%. The test procedures will be based on AASHTO T322. E* in IDT Mode is needed to evaluate the mix property at low temperature, which is not possible in the AMPT as per AASHTO TP62. The IDT E* test will be conducted by WSU team.
- Flow Number Test: As per AASHTO TP79, the flow number is a property related to the resistance of HMA to permanent deformation. It can be used to evaluate and design HMA with specific resistance to permanent deformation. This test shall be used to predict the potential of rutting resistance of the four designated mixes.
- Creep Compliance: Creep compliance in IDT will be conducted at different temperatures (-20, -10, 0, 10, 20, and 30ºC). The mixtures will be long-term aged in accordance with the AASHTO R30. Three replicates will be used for each of four mixes. The air void of the specimens will be 4±0.5%. The test procedures will be based on AASHTO T322.
- Fatigue: For bottom-up fatigue cracking, the fracture work density from IDT test has been found to relate to the field performance and will be used as fatigue indicator of the materials (Wen 2012). Fracture work density is the area underneath the stress and strain curve up to the zero stress level. It accounts for both strength and ductility of HMA. The mixtures will be long-term aged in accordance with AASHTO R30. Three replicates will be used for each of four mixes. The air void of the specimens will be 4±0.5%. The tests will be conducted at 20ºC. The test procedures will be based on AASHTO T322.
- Transverse cracking: Fracture work density of asphalt mixes from indirect tensile test at low temperature has been found to be able to correlate with the field performance of transverse cracking (Wen et al 2013). The mixtures will be long-term aged in accordance with AASHTO R30. Three replicates will be used for each of four mixes. The air void of the specimens will be 4±0.5%. The tests will be conducted at -20ºC. The test procedures will be based on AASHTO T322.
- Studded Tire Wear: WSU has developed a studded tire wear simulator which will be used to determine the resistance of the field samples to studded tire wear. The effects of fiber on the resistance of mixes to studded tire wear will be determined. The mixtures will be short-term aged in accordance with AASHTO R30. Three replicates will be used for each of four mixes. The air void of the specimens will be 7±0.5%. The tests will be conducted at 20ºC.
- APA test: Evaluation of mix resistance to rutting using the Asphalt Pavement Analyzer (APA) has been recommended by AASHTO and ITD uses it on routine basis. This test shall be conducted in accordance to AASHTO TP63 by ITD at ITD-HQ lab since neither U of I nor WSU has the APA machine. Test results shall be delivered to U of I team and will be included in the analysis in the final report.
Task 5: Performance Prediction using AASHTOWare ME Design Software:
To evaluate the expected performance of the proposed mixes and test sections, AASHTOWare ME-Design software will be run for various scenarios to compare among the predicted performance. For this purpose, Level 1 will be adopted for HMA properties where for other layers, either level 2 or 3 will be adopted based on the data availability for the base/subbase and subgrade layers. Also, the traffic scheme will be adopted form the nearest WIM station. In the ITD traffic database, there are three WIM stations, Number 133, 134 and 155. In consultation with ITD committee, a station will be selected for traffic data input in the ME software. It is assumed that access to ME Software will be provided by ITD. In case the software is not available or accessible by U of I Team, the research team will rely on the research version of the software, MEPDG 1.0.
Task 6: Evaluation of Fiber Dispersion in the Mix Using X-Ray Tomography:
Based on communication with the project advisory committee, there was a need to evaluate the level of dispersion of the fiber in the mix as it plays a major role in the mix performance. Literature indicates that such a need can be attained by using X-Ray Tomography. Hence, this task is added and will be performed at WSU. To detect the dispersion of the fibers in the mix, field core samples would be more appropriate. Field cores will reflect not only, the mix design parameters of each mix but also the quality of construction in each strip. However, since lab testing (Task 4) will be performed on lab compacted samples, and to maintain consistency, the researchers may consider performing X-ray tomography on two samples for each mix, one from field cores and one as lab compacted specimen. Core samples will be procured from the field by ITD, in coordination with U of I team, using standard ITD coring methods. Scanning of the samples will be initiated with Flash CT Data Acquisition (DAQ), which is a specifically devised acquisition tool that controls hardware operations, calibration and scanning. After the scan parameters are entered, the sample is rotated such that radiographic images at the desired angles can be collected.
Task 7: Modeling Fiber-Reinforced HMA:
This task was added as a research task to review the literature with regard to the models that may be available to predict performance of Fiber-Reinforced HMA. There is a lot of work in this area with regard to cementitious materials. In this task, the fiber reinforced concrete models will be reviewed and investigate the applicability of such models to HMA. Depending on the findings of this task, more lab testing may be required, and that may lead to project time and budget extension. Findings will be communicated to ITD to decide whether an amendment to the project is warranted.
Task 8: Development of the Final Report:
Reporting will follow the regular monthly report system with ITD. Progress meetings with ITD will be planned to update ITD on the project findings. This task will be dedicated to writing the final report after all research work is complete.
Project Communication Schedule:
A monthly progress report will be submitted on Form 771 as per ITD requirements. In addition, an interim project meeting will be held to present progress at each completed mile stone. One TAC meeting will be held upon completion of the project construction. Another TAC meeting will be held upon completion of lab testing, and then a final project meeting will be held upon completion of the final report.
Needs and Requirements:
This project is cooperative between ITD and U of I and WSU as sub-award to U of I. While U of I is responsible for all the tasks listed above, it is understood and assumed that ITD shall be responsible for:
- Overseeing the project construction and developing the construction documents.
- Coordinating the collecting the plant mix samples and all materials from the field and providing them to U of I.
- Providing access to use AASHTOWare ME Pavement Design Software.
- Conducting field performance evaluation, including FWD, of the road section under study, in coordination with the pavement management unit at ITD. This is needed before milling and after construction to establish initial performance record. Provide raw and analyzed data to U of I team.
- Conducting the APA testing for all mixes as per Item h under Task 4.
Required Outputs:
U of I will deliver the final report that describes the project documentation, lab test results and drawn conclusions.
U of I will hold a final project meeting / workshop to present all the achieved results and outcomes.
Implementation:
The outcomes of this project can be implemented in the form of guidelines and recommendations of modifying HMA mixes with fibers if found feasible and cost effective.
Expected Outcomes/Savings to ITD:
The lab study will complement the field pilot project to document all material properties and prepare data for the application of the AASHTOWare ME Pavement Design software, which is needed for pavement design of the fiber-reinforced HMA mixes. In addition, the lab testing will provide initial performance evaluation of these mixes to be validated in the field during the subsequent phases of the project.
The outcomes of this research shall help ITD assess the effectiveness and potential cost savings of using fibers to mitigate cracking and rutting problems on the state roads.
There expected great benefits from using fiber-reinforcement in HMA to arrest cracking and resist rutting, which shall intuitively enhance safety and reduce maintenance cost. The work will provide data to quantify the cost savings if any and added value for better performance.