Opportunities for Incorporating Performance Evaluation into Mix Design, Construction, and Acceptance

Transcription

1 Opportunities for Incorporating Performance Evaluation into Mix Design, Construction, and Acceptance By Andrew Hanz, Ph.D. Gerald Reinke MTE Services Inc. July 17, 2014

2 HMA Monitoring and Acceptance Volumetric Properties Mix Composition Moisture Damage In-Place Density Smoothness Distress Test Rutting Hamburg, FN Fatigue Thermal Cracking Beam, SCB, Uniaxial, IDT Dc(t),IDT, ATCA Design E* Daily Sampling: Surrogate tests to estimate performance. Mechanical Testing: Verify properties measured in mix design at a reasonable sampling frequency. Frequency: Point vs. Continuous measures (i.e. PSPA and IC) Type: Destructive vs. Non-Destructive

3 Performance Evaluation in Mix Design 1. Materials Selection 2. Design Aggregate Structure 3. Determine Optimum AC 4. Moisture Damage Evaluation PG Selection to account for RAP/RAS Assess need for Grade Dumping Evaluate different oil modifications. Obtain better estimate of rheological properties. Balanced Mix Design Concept Maximum Rutting Limit Minimum Fracture Energy for Fatigue and Thermal Cracking (northern states?) Must meet both volumetric and performance criteria. 5. Design Input Modulus Value for M-E Design Modeling: Hirsch/Witzcak Direct Measurement

4 Binder Evaluation for High RAM Mixes Direct Measurement 4mm PP Effect of Aging PG Grading Rheological Index (R) OB RTFO PAV1 PAV2 20%RAS+ 5% Oil 1 20%RAS+5%Oil 2 Extrapolation of 8 mm Data Binder LT PG Grade OB RTFO PAV1 PAV % RAS +5% Oil 1 20% RAS + 5% Oil 2 1. Anderson, et al., Binder Characterization and Evaluation Volume 3: Physical Characterization. SHRP A-369 Report, National Research Council, Farrar, Sui, et al. 4 mm Plate Development TRB 2011, 2012, Eurobitume2012 and others.

5 Application and Verification -Trial Section US Hwy 14 4 mixes placed on shoulders in Sept PG 58-28, 0% RAS, 20% RAP, (21% PBR) JMF PG 58-28, 0% RAS, 31% RAP, (32% PBR) PG 58-28, 6% RAS (22% PBR), 11% RAP (12% PBR) PG 52-34, 6% RAS (22% PBR), 11% RAP (12% PBR) Field Cores 1 month after construction aged 0, 5, and 10 days at 85 C. 1 year after construction No aging, top 12mm and 2 nd 12mm tested. Testing Mix stiffness torsion bar Recovered Binder Properties 4 mm DSR Chemical Analysis - Iatroscan For more information: Reinke, et. al., Impact of RAS on Mixture and Recovered Binder Properties, Paper 1172, ISAP 2014.

6 Effects of Aging on Mechanical Properties ΔTC (M CRITICAL TEMP -S CRITICAL TEMP, C) UNAGED THE MORE NEGATIVE THE DIFFERENCE OF M -S CRITICAL TEMPERATURES THE MORE M CONTROLLED IS THE BINDER and Chemistry 5 DAY 0.4 ASPHALTENE, % DAY Hwy 1411% RAP, 6% RAS, PG Hwy 1431% RAP, 0% RAS PG Hwy 1420% RAP, 0% RAS, PG Hwy 1411% RAP, 6% RAS, PG Note: datavalues in colored boxes are the M-S critical temperatures for the respectively colored data curves at 0, 5 and 10 days of core 85 C -6.8

7 How does laboratory aging protocol relate to the field? MIX TORSION BAR TEST ASTM D mm X 12 mm X 7 mm TESTED AT -40 C TO DEPENDING ON MIX STIFFNESS Objectives Verify that the aging conditions selected are representative of what occurs in the field. Compare results of field aged RAP/RAS mixes to laboratory aged core results. *Will focus on low frequency end of master curve to compare values of stiffness. Data available: 2012 Cores: Taken one month after construction and aged at 85 C for 0, 5, and 10 days Cores: Taken one year after construction and tested.

8 G* FOR 6% RAS, 11% RAP MIXES PG 0, 5 & 10 DAYS 85 C 2012 and Cores from E+09 STIFFNESS MODULUS G*, Pa 1.0E E+07 mix is the same or a greater 1.0E+06 than the 5 day aged Data for 2013 cores --- Data for 2012 cores The mix stiffness data for the PG mix shows that the modulus of the top 12 mm of the 1 year old field original mix while the 2 nd 12 mm layer is similar to the stiffness of the 5 day aged mix. 1.0E E E E E E E E E E E E+03 FREQUENCY, RAD/SEC 2012 Core 0 Day 85 C 2013Core -Top 12mm Rep Core 5 85 C 2013Core Top 12 mm Rep Core C 2013 Core 2 nd 12mm

9 Effect of Reducing Binder Grade: G* for 6% RAS, 11% RAP MIXES PG 0, 5, 10 DAYS AGING 2012 CORES and CORES TAKEN in E+09 COMPLEX SHEAR MODULUS, G*, Pa Data for 2013 cores --- Data for 2012 cores 1.0E E+07 The mix stiffness data for the PG mix shows that the modulus of the top 1.0E mm of the 1 year old field mix is the same or a little greater than the 5 day aged original 1.0E E E E E E E E E E E E+03 REDUCED FREQUENCY, RAD/SEC 2012 Core 0 Day 85 C 2013Core -Top 12mm Rep Core 5 85 C 2013Core Top 12 mm Rep Core C 2013 Core 2 nd 12mm

10 Aging Summary of Findings Consideration of multiple aging conditions is necessary. Aging vs. ΔTc relationship was not linear. Study was focused on mixtures and recovered binders to best simulate thin film condition in the field. Can also study relationships with RTFO and PAV aging of binder. Effects of RAP and RAS For a given binder replacement, the rate of aging and embrittlement of high RAP mixes was significantly lower relative to RAS. This can be remedied by softening the binder grade and/or use of rejuvenating additives.

11 Balanced Mix Design Concept LT (-22 to -34 C) Thermal Cracking TSRST or DC(t) IT (15-25 C) Fatigue Semi-Circular Bend HT (~50 C) Rutting Hamburg or FN

12 Balanced Mix Design 1. Establish AC content by volumetrics 2. Verify Performance Challenges Corrective Action Binder vs. Aggregate Structure Contribution Field Verification σtest vs. σproduction Lab vs. Field Aging Surrogate test methods Cooper, S. Testing and Analysis of LWT and SCB Properties of Asphalt Mixtures Louisiana Transportation Conference, 2013.

13 RUT DEPTH IN HAMBURG PASSES Effects of Aggregate Structure and Binder Properties on LWT RUT DEPTH AS A FUNCTION OF SVF FOR ALL MIXES FOR ALL TEST LOADS E N--R 2 = E N--R 2 = E N--R 2 = E N--R 2 = E N--R 2 = E N--R 2 = E N--R 2 = E N--R 2 = E N--R 2 =0.86 Higher ηand more stress tolerance = better rutting resistance E1 890N 2. E10 890N 3. E1 703N 4. E1 534N 5. E10 534N 6. E10 7. E10 8. E10 534N 9. E10 703N SVF = η* x Stress at 70% η*initial SVF Reinke, G., et al. Utilization of Binder Stress Sensitivity to Investigate the Impact of Applied Load, Binder Type, and Aggregate Structure on the Rutting Behavior of Bituminous Mixtures. Eurobitume, 2008.

14 Aggregate Structure Effect on Thermal- Volumetric Properties Thermal Strain (%) Low connectivity High connectivity Temperature ( C) Bahia, Hanz, Roohi, UW-MARC Mixing and Compaction Temperature Workshop UW Madison,

15 Direct Measurement of Aggregate Structure Image Analysis 2D Scan of mix image using bench top scanner. Example: IPas2 Software (UWMARC) Sefidmazgi, N. R., Tashman, L., and Bahia, H., "Characterization of Asphalt Mixture Rutting Performance Using 2-D Imaging Internal Structure Parameters," Journal of the Association of Asphalt Paving Technologists, Vol. 81, 2012, pp

16 Flow Number Relations to Performance Image Rutting Resistance R² = 0.90 Analysis E3 E10 E Contact Length (mm/100cm^2) CTE (1/ C) 6.50E E E E E E E-05 Thermal Contraction 3.00E Contact Length 1. Sefidmazgi, N. R., Teymourpour, P., Bahia, H. U. " Effect of Particle Mobility on Aggregate Structure Formation in Asphalt Mixtures, "Journal of the Association of Asphalt Paving Technologists, Vol. 82, 2013, pp Teymourpour, P.; Bahia, H.U.; "Role of Asphalt Modification In Achieving Better Aggregate Packing Structure And Performance," Proceedings of the 58th Annual Conference of the Canadian Technical Asphalt Association (CTAA), 2013.

17 Direct Measurement of Aggregate Structure Shear Forces during Compaction Eccentricity e = Eccentricity P = Pressure in the Gyratory A = Sample Area Relation to Mix Stability h = Sample Height ve_gyratory_compactor_t312_asphalt/main

18 Relations to Performance Shear Measurement During Compaction Mold R e Ram HMA Sample o 1.25 GLPA y = x R 2 = TFI FN Faheem, Bahia, Using the Gyratory Compactor to Measure the Mechanical Stability of HMA Mixtures. Wisconsin Highway Research Program, WisDOT, 2004.

19 Example: Inconsistent Stability During Production 'e' (inches) Count E1 Wimmie E1 Wimmie E1 Wimmie E1 Wimmie E1 Wimmie E1 Wimmie

20 Summary of Findings Performance related test methods for asphalt characterization are well established. There are opportunities to move beyond classifying aggregate structure based solely on gradation (i.e. fine and coarse) or mix classification (i.e. E1 vs. E10). These tools allow for assessment of how the aggregate and binder interact to form the final aggregate structure.

21 From Mix Design to Production Performance Testing Concerns Variability of Production vs. Test Method Is test sensitive enough to detect changes in mix composition? Aging Short Term Aging: Protocol needed to ensure lab and plant produced mixes experience similar aging before testing. Long Term Aging: Aging protocol that relates to critical condition in the field.

22 Effects of Variation in Dust and Asphalt Contents on FN Bonaquist, R., Evalutionof Flow Number as a Discriminating Mixture Property. Wisconsin Highway Research Program Report , WisDOT, 2012

23 Effects of Deviation in Design Air Void Content on FN Samples taken from resulting changes in air void content from varying P200 and %AC Poor relationship indicates that controlling air void content during production does not necessarily ensure rutting resistance. Bonaquist, R., Evalutionof Flow Number as a Discriminating Mixture Property. Wisconsin Highway Research Program Report , WisDOT, 2012

24 Short Term Aging -Preliminary Results: Capitol Dr. Field Project Flow Number (FN) Design Day 1 Day 2 Day 3 Bonaquist, Bahia, Hanz, Velasquez, WHRP Project Research in Progress, final report under review.

25 Long Term Aging Concerns ΔTc = m(crit) -S(crit) Recall data from Slide 6 Days Mix Aging at 85 C PG 58-28,20% RAP, 0% RAS PG 58-28, 31%RAP, 0%RAS PG 58-28, 11% RAP, 6% RAS PG 52-34, 11% RAP, 6%RAS Does evaluating cracking resistance on plant produced samples or even after 5 days aging represent possible differences in performance late in service life? Research needed.

26 Example: Framework for Performance Mix Characteristic Recycled Materials Volumetrics Rutting Resistance Fatigue Cracking Thermal Cracking Related Mix Evaluation Mix Design Rheologyof extracted binders at different aging. Current specifications + Imagingor Shear Measurement LWT,FN or irlpdon unaged 50 C SCB@ PG ITafterlong term aging Dc(t)@ LT PG+10 after long term aging Production (Daily) Gradation and %AC Imageanalysis, shear measurement, or other methods Notes: 1. Hamburg, Dc(t), and SCB are currently under consideration by WisDOT for evaluation of high RAM mixtures. Current Specifications Production(every XX,000 tons) Rheology of extracted binder. Mix Performance Test

27 Thank You! Acknowledgements P3 Symposium organizing committee. WHRP Flex TOC UW Modified Asphalt Research Center Construction/MTE Andrew Hanz MTE Services Inc