Using Recycled Asphalt Shingles with Warm Mix Asphalt Technologies

Due to the increased use of recycled materials in pavement, the crack resistance of asphalt mixtures has become a major concern. This study evaluated the crack resistance of asphalt mixtures containing up to 40% reclaimed asphalt pavement (RAP) at intermediate temperatures. Three groups of materials consisting of seven plant-produced hot-mix asphalt mixtures were evaluated. A suite of test methods with various mechanistic backgrounds were employed, namely: semi-circular bend, simplified viscoelastic continuum damage, indirect tension, Texas overlay, and Illinois flexibility index tests. The corresponding parameters obtained for assessing crack resistance were: critical strain energy release rate Jc, material fatigue sensitivity, dissipated creep strain energy, number of cycles to failure Nf,OT, the interaction plot of critical fracture energy versus crack progression rate, and the flexibility index, respectively. Test results indicated that mixtures with higher RAP content exhibited higher stiffness and indirect tensile strength with lower compliance than the counterpart materials. In addition, all evaluation parameters, except for the use of the interaction plot from the Texas overlay test, provided consistent observations that incorporation of more RAP deteriorated the materials’ crack resistance. The mixture-discriminating capabilities of all test methodologies were also investigated using the paired t-test on the experimental data of each mixture group. The results presented herein were part of Pooled Fund TPF-5(294) study titled Develop Mix Design and Analysis Procedures for Asphalt Mixtures Containing High-RAP and/or RAS Contents.

Section: Test Methodsmentioning

confidence: 99%

Comparison of Asphalt Mixtures Crack Resistance at Intermediate Temperatures using Advanced Test Methods and Theories

Cao

Mohammad

Barghabany

et al. 2018

“…For example, this balance can be achieved by increasing the asphalt binder content of a “dry” mix to improve its cracking resistance while maintaining its rutting resistance within an acceptable range. In addition to asphalt binder content, BMD is applicable to many other mix design variables such as aggregate gradation, recycled asphalt materials content, asphalt additive, and asphalt binder type and grade ( 5 ).…”

Section: Literature Reviewmentioning

confidence: 99%

“…BMD is defined as “asphalt mix design using performance tests on appropriately conditioned specimens that address multiple modes of distress taking into consideration mix aging, traffic, climate and location within the pavement structure” ( 5 ). The goal of BMD is to achieve a balance between the rutting resistance and cracking resistance of asphalt mixtures by conducting performance testing in addition to or as replacement of the traditional volumetric analysis.…”

Section: Literature Reviewmentioning

confidence: 99%

Evaluating Impact of Corrected Optimum Asphalt Content and Benchmarking Cracking Resistance of Georgia Mixtures for Balanced Mix Design Implementation

Sala

Tran

Yin

et al. 2022

The Georgia Department of Transportation (GDOT) implemented the corrected optimum asphalt content (COAC) approach to reducing the allowable reclaimed asphalt pavement (RAP) binder contribution for improving mixture durability. The COAC of 60:40 implemented in 2019 allows 60% of the RAP binder to be credited to the total mix, requiring additional virgin asphalt binder equivalent to 40% of the RAP binder to be added to the volumetric optimum binder content. To further enhance the durability of asphalt mixtures, GDOT plans to implement the indirect tensile asphalt cracking test (IDEAL-CT) in the balanced mix design (BMD) method in conjunction with the Hamburg wheel tracking test that is currently specified in the GDOT specifications. To assist GDOT in the implementation effort, this study was conducted to (1) evaluate the effect of the COAC approach on the cracking and rutting resistance of asphalt mixtures using the proposed BMD test methods; and (2) benchmark the cracking resistance (i.e., CTindex) of plant-produced mixtures being produced in the state of Georgia for developing CTindex thresholds for future implementation. The results of this study suggest that the 60:40 COAC helps improve the cracking resistance of asphalt mixtures containing high RAP contents with minimum effect on their rutting resistance when compared with the corresponding virgin mixtures. In addition, because of statistical differences in the CTindex results between stone mastic asphalt (SMA), surface, and intermediate/base mixtures tested in this study, different CTindex thresholds are proposed for these three mixture groups for pilot projects. Further research is anticipated to refine these thresholds and verify with field performance for future implementation in mix design approval and acceptance testing.

“…Many field test sections have been constructed in the past and the field performance of each test section has been surveyed and documented in the literature. The authors reviewed field performance for a total of 206 test sections constructed under NCHRP 9-47A ( 10 ), 9-49A ( 11 ), 9-55 ( 12 ), and 9-58 ( 13 ), pooled fund study TPF-5(213) ( 14 ), and the Texas Department of Transportation’s research projects 0-6092 ( 15 ), 0-6614 ( 16 ), 0-6738 ( 17 ), and 0-6674 ( 18 ). These test sections were constructed to evaluate the performance of asphalt mixes with recycled materials, warm mix technologies, rejuvenators, high asphalt contents, and softer but polymer modified asphalts.…”

Section: Field Performance and Pavement Lives Of Various Asphalt Over...mentioning

confidence: 99%

Short- and Mid-Term Loose Mix Conditioning Protocols for Asphalt Overlay Balanced Mix Design and Quality Control and Quality Acceptance

Zhou

Mogawer

Steger³

2022

Many aspects of balanced mix design (BMD) and performance-related quality control and quality acceptance (QC/QA) testing depend heavily on how the asphalt mixes are conditioned. There is, therefore, a critical need for practical loose mix conditioning protocols. The main objective of this study was to establish practical loose mix condition protocols for both the BMD and QC/QA phases. To develop these protocols, this paper reviewed the field performance and pavement lives of more than 200 test sections around the United States and found most of these test sections were 50-mm thick asphalt overlays where cracking is evident in 1 to 4 years. Based on this finding, the paper developed two conditioning protocols for asphalt overlays: short-term and mid-term. The short-term conditioning is intended for volumetric design, BMD rutting performance test, and QC/QA testing at asphalt plants, while the mid-term conditioning is mainly for BMD cracking performance test. A series of IDEAL cracking tests were then conducted with 13 mixes and the test results confirmed the validity of the mid-term conditioning protocol. It was also found that conditioning time affected mix cracking resistance significantly. The longer the conditioning time, the poorer the cracking resistance. When conditioned too long, the normalized cracking resistance difference among various mixes diminished. For asphalt mix composition, binder source (or quality) and asphalt absorption are two significant factors affecting the normalized cracking resistance of asphalt mixes; in contrast, mix type, asphalt binder content, and the use of rejuvenator had insignificant influence.