Effect of Aggregate, Binder, and Warm-Mix Additive Interaction on the Durability of Asphalt Mixtures

Transcription

1 Effect of Aggregate, Binder, and Warm-Mix Additive Interaction on the Durability of Asphalt Mixtures PAVEMENT PERFORMANCE PREDICTION SYMPOSIUM Elie Y. Hajj, Ph.D. Western Regional Superpave Center University of Nevada, Reno July 12, 2012 Laramie, Wyoming

2 Introduction Is the effect of warm-mix additives on the durability of asphalt mixtures materials dependent? Durability can be assessed in terms of the mixture resistance to moisture damage. 2 Univ. of Nevada, Reno (

3 Moisture Damage Function of Aggregate/Asphalt compatibility in the presence of water. An adhesion loss between asphalt binder and aggregate. A cohesion failure of asphalt mastic bond due to interaction with moisture. No Moisture- Induced Damage Moisture- Induced Damage 3 Univ. of Nevada, Reno (

4 Moisture Damage in WMA Potential Sources Lower production temperatures: Incomplete aggregate drying Bonding of asphalt to aggregate Reduced binder stiffness WMA additive Mitigation Strategies WMA additive selection Temperature selection Additional additive use to mitigate stripping potential Maintaining dry aggregates 4 Univ. of Nevada, Reno (

5 Findings of Two On-going Studies ARC Study Subtask E1c-1: Warm Mixes: UNR-UWM Adhesive properties of WMA modified binders & moisture damage susceptibility of WMA mixes. SDDOT Study: UNR Evaluation of WMA concrete pavement in South Dakota conditions 5 Univ. of Nevada, Reno (

6 ARC Subtask E1c-1: Warm Mixes 6 Univ. of Nevada, Reno (

7 ARC Subtask E1c-1: Warm Mixes Moisture Damage of WMA Mixes Investigate the influence of low production temperatures, aggregate moisture, & WMA additives on adhesive properties of WMA modified binders & moisture damage susceptibility of WMA mixes. 7 Univ. of Nevada, Reno (

8 ARC Subtask E1c-1: Warm Mixes Experimental Plan Factor Levels Value Asphalt Binder Grade 2 PG64-22 PG76-22 (SBS) WMA Additive 4 None WB (0.25% by wt. of mix) PS (2.0% by wt. of binder) VR (0.50% by wt. of binder) Aggregate Type 2 Granite (WI) Rhyolite (NV) Total Combinations 16 WB- Water bearing additive PS- Pelletized surfactant VR- Viscosity reducer 8 Univ. of Nevada, Reno (

9 ARC Subtask E1c-1: Warm Mixes Mix Design Mix Design parameters Rhyolite (NV) Granite (WI) NMAS (inch) 1/2 3/4 Aggregate Absorption (%) Binder Content (%) Superpave mix design for fine graded aggregate Medium traffic level (3-10 millions ESALS) Mix design for control mix was verified for WMA mixes 9 Univ. of Nevada, Reno (

10 ARC Subtask E1c-1: Warm Mixes Mixtures Testing AASHTO T283: Tensile strength ratio, TSR IDT at 77 F Undamaged = 0 F-T cycle Moisture damage = 1 F-T cycles AASHTO TP79 + T283: Dynamic modulus stiffness ratio, ESR E* at 68 F and 10, 1, 0.1 HZ Undamaged = 0 F-T cycle Moisture damage = 3 F-T cycles 10 Univ. of Nevada, Reno (

11 ARC Subtask E1c-1: Warm Mixes Mixture Samples Preparation Mixing considering Residual Moisture due to insufficient aggregate drying Short-term aging of loose mixes HMA: 4 hrs at 275 F (AASHTO R30) WMA: 2 hrs at compaction temperature (NCHRP Report 691) WMA w/o additives: 2 hrs at compaction temperature Target air voids: % Freeze-thaw (F-T) cycling for moisture damage 1 F-T consists of: freezing at 0 F for 16 hrs, thawing at 140 F for 24 hrs, followed by 2 hrs at 77 F 11 Univ. of Nevada, Reno (

12 ARC Subtask E1c-1: Warm Mixes Mixture Samples Preparation Residual Moisture Process: Add 2% water above SSD & soak for hrs: moist aggregate Calibration time: 100% dried moist agg. at HMA mixing temp. Use calibration time to heat moist aggregate at WMA mixing temp. Moisture left in WMA agg. is: residual moisture 12 Univ. of Nevada, Reno (

13 ARC Subtask E1c-1: Warm Mixes Mixture Samples Preparation Mixing Temperature Average Residual Compaction ( F) Moisture (%) Mixture Type Temperature Binder Aggregate ( F) Rhyolite, Granite, NV WI HMA, control WMA without additive WMA with WB WMA with PS WMA with VR Mixing temperatures of WMAs are determined per NCHRP Report 691 Compaction Temperature is 20 F below mixing temperature No hydrated lime or liquid anti-strip was introduced 13 Univ. of Nevada, Reno (

14 ARC Subtask E1c-1: Warm Mixes Indirect Tensile Strength Results Undamaged ITS (psi) Moisture-damaged ITS (psi) PG PG PG PG Granite Rhyolite HMA WMA w/o additive WB-0.25% TWM PS-2% TWB VR-0.5% TWB F-T Cycle PG PG PG PG Granite Rhyolite HMA WMA w/o additive WB-0.25% TWM PS-2% TWB VR-0.5% TWB 14 Univ. of Nevada, Reno (

15 ARC Subtask E1c-1: Warm Mixes Indirect Tensile Strength Results 100 TSR (%) PG PG PG PG Granite Rhyolite HMA WMA w/o additive WB-0.25% TWM PS-2% TWB VR-0.5% TWB 15 Univ. of Nevada, Reno (

16 ARC Subtask E1c-1: Warm Mixes Dynamic Modulus Results 3 F-T Cycles 16 Univ. of Nevada, Reno (

17 ARC Subtask E1c-1: Warm Mixes Dynamic Modulus Results 17 Univ. of Nevada, Reno (

18 ARC Subtask E1c-1: Warm Mixes ANOVA p-values (ITS) p-values ( E* ) Factor Dry Strength Wet Strength E* Undamaged E* Moisture- Damaged Binder Aggregate WMA Additive Aggregate Source Effect: Significant for ITS test and Undamaged E*. WMA Additive Effect: Significant for Moisture damaged ITS and E*. Insignificant for undamaged ITS. 18 Univ. of Nevada, Reno (

19 ARC Subtask E1c-1: Warm Mixes TSR vs. ESR ESR at 68 F after 3 F-T Cycles (%) R² = TSR at 77 F after 1 F-T Cycle (%) HMA WMA w/o additive WB-0.25% WTM PS-2% TWB VR-0.5% TWB 19 Univ. of Nevada, Reno (

20 EVALUATION OF WMA MIXES IN SOUTH DAKOTA 20 Univ. of Nevada, Reno (

21 Evaluation of WMA Mixes in SD Materials and WMA Technologies Materials Aggregates: 3 sources Quartzite, Limestone, & Natural Gravel Asphalt binder: 1 source (PG64-28) Hydrated lime: 1% by DWA WMA Technologies Advera (0.3% by TWM) Evotherm 3G (0.5% by TWB) Plant Foaming Process (1.5% by TWB) 21 Univ. of Nevada, Reno (

22 Evaluation of WMA Mixes in SD Mixing/Compaction Temperatures Mixing/Compaction Temperatures ( F) Following NCHRP 9-43 Procedure HMA HMA-2hrs STOA WMA w/o Additive WMA- Advera WMA- Evotherm WMA- Foaming Quartzite 325/ / / / / /240 Limestone 325/ / / / / /260 Natural Gravel 325/300 Not Tested 265/ / / /260 Residual moisture was not considered in this study. 22 Univ. of Nevada, Reno (

23 Evaluation of WMA Mixes in SD Quartzite Aggregates + PG64-28 Indirect Tensile Strength at 77 F, psi HMA HMA-2hrs STOA WMA w/o Additive Mixture Type WMA-Advera WMA-Evotherm WMA-Foaming Dry ITS, psi Wet ITS, psi Tensile Strength Ratio (TSR) Tensile Strength Ratio at 77 F, % 23 Univ. of Nevada, Reno (

24 Evaluation of WMA Mixes in SD Limestone Aggregates + PG64-28 Indirect Tensile Strength at 77 F, psi HMA HMA-2hrs STOA WMA w/o Additive Mixture Type WMA-Advera WMA-Evotherm WMA-Foaming Dry ITS, psi Wet ITS, psi Tensile Strength Ratio (TSR) Tensile Strength Ratio at 77 F, % 24 Univ. of Nevada, Reno (

25 Evaluation of WMA Mixes in SD Natural Gravel Aggr. + PG64-28 Indirect Tensile Strength at 77 F, psi HMA HMA-2hrs STOA WMA w/o Additive Mixture Type WMA-Advera WMA-Evotherm WMA-Foaming Dry ITS, psi Wet ITS, psi Tensile Strength Ratio (TSR) Tensile Strength Ratio at 77 F, % 25 Univ. of Nevada, Reno (

26 Evaluation of WMA Mixes in SD Grouping by Aggregate Source 180 Dry ITS at 77 F, psi Quartzite Limestone Natural Gravel HMA HMA-2hrs STOA WMA w/o Additive WMA-Advera WMA-Evotherm WMA-Foaming 26 Univ. of Nevada, Reno (

27 Evaluation of WMA Mixes in SD Grouping by Aggregate Source 180 Wet ITS at 77 F, psi Quartzite Limestone Natural Gravel HMA HMA-2hrs STOA WMA w/o Additive WMA-Advera WMA-Evotherm WMA-Foaming 27 Univ. of Nevada, Reno (

28 Evaluation of WMA Mixes in SD Grouping by Aggregate Source 100 TSR at 77 F, % Quartzite Limestone Natural Gravel HMA HMA-2hrs STOA WMA w/o Additive WMA-Advera WMA-Evotherm WMA-Foaming 28 Univ. of Nevada, Reno (

29 Evaluation of WMA Mixes in SD ANOVA Analysis Source Dry ITS P-Value Significance* Agg. Type < HS WMA Trt < HS (Aggregate Type) (WMA) Treatment < * NS - Not Significant LS Low Significant HS-High Significant HS 29 Univ. of Nevada, Reno (

30 Overall Summary of Findings ARC Subtask E1c-1: Compatibility problem between WB additive & Granite aggregate. Pelletized surfactant (PS) resulted in the best moisture damage resistance followed by the VR chemical additive. SDDOT Mixes Aggregate type, Mix type (WMA additive) & their interactions significantly impact the dry & wet TS values of the asphalt mixtures. Ranking of the mixtures resistance to moisture damage varied with the aggregate sources for the same asphalt binder. 30 Univ. of Nevada, Reno (

31 Overall Summary of Findings Is the effect of warm-mix additives on the durability of asphalt mixtures materials dependent? 31 Univ. of Nevada, Reno (

32 THANK YOU FOR YOU ATTENDANCE Visit our websites at: Univ. of Nevada, Reno (