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Department of Civil Engineering Kansas State University

Evaluation of Cracking Resistance of Superpave Mixtures Using Texas Overlay Test. Syeda Rubaiyat Aziz Mustaque Hossain Greg Schieber. Department of Civil Engineering Kansas State University. Outline . Background Objective Materials & Test Method Laboratory Testing Results

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Department of Civil Engineering Kansas State University

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  1. Evaluation of Cracking Resistance of Superpave Mixtures Using Texas Overlay Test SyedaRubaiyatAzizMustaqueHossainGreg Schieber Department of Civil EngineeringKansas State University

  2. Outline • Background • Objective • Materials & Test Method • Laboratory Testing • Results • Conclusions & Recommendations • Acknowledgements

  3. Research Background • About 94% of paved road in the United States is Hot-Mix Asphalt (HMA) • Annual HMA production is about 500-550 million tons • Reasons for increased use of reclaimed asphalt pavement (RAP): • Rise in oil price, emphasis on sustainability, limited virgin aggregate availability • High RAP content sometimes leads to drier mix, prone to early cracking

  4. Objective • Investigate cracking resistance of Superpave mixtures with varying RAP content • Investigate effect of RAP source on cracking resistance

  5. Materials & Test Method • Materials: Superpave 12.5-mm NMAS mixture with PG 70-28 • Five virgin aggregates • Three RAP contents (20%, 30% and 40%) • Twosources • Test: Texas Overlay Test and Semi-Circular Bending Test

  6. Aggregate BlendingSR-12.5A (with RAP) First RAP source (Shiling) Second RAP source (Konza)

  7. Texas Overlay Test (TEX-248-F) • Simulates opening or closing of joints, which accelerates crack initiation and propagation • Controlled displacement mode • Test performed at 25° C

  8. Texas Overlay Test (Cont…) • After cutting, air void is checked (7±1)%, then glued on base plates • 3 replicates from each Mixture Courtesy: TTI manual Tex-248-F

  9. Texas Overlay Test (Cont…) • Initial load • % of load reduction • No of OT cycles of failure

  10. Semi-circular Bending Test (SCB) • Half disc shaped (3’’ diameter, 2’’ thick) • Must satisfy 7±1 % air void • Notched at bottom • Three point bending setup • Loaded in compression • Test temperature at 25° C • 3 Static & 12 Cyclic test specimens for each mixture

  11. SCB Test (Cont…) 2S 2R S = 0.8 R s = 0.8 R

  12. Results

  13. Results (Overlay Test)

  14. Repetitive SCB Test Shiling RAP

  15. Statistical AnalysisComparison of Means OT Test R-SCB Test *Mix types not connected by same letter have statistical significant difference

  16. Conclusions • Based on the Texas Overlay test results: • Increase in RAP content reduces cracking resistance • Overall, mixtures with first RAP source carried higher no. of OT cycles prior to failure compared to second RAP source • Based on SCB test results: • Similar trend of results as OT tests were obtained • 20% RAP performed well for first RAP source and 40% RAP performed well for second RAP source

  17. Recommendations • Study more RAP sources • Correlate cracking test results with actual field data

  18. Acknowledgements • This study has been sponsored by the Kansas Department of Transportation (KDOT)

  19. Thank You!

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