Semi Circular Bend Test:

Transcription

1 Semi Circular Bend Test: And Industry Initiative Towards Performance Based Testing Plant Certification Program Update/Refresher Course Outline A Review of Asphalt Concrete Fatigue Tests Semi Circular Bend (SCB) Test PSU SCB Study and Preliminary Results Industry Initiative Summary 2 1

2 Outline A Review of Asphalt Concrete Fatigue Tests Semi Circular Bend (SCB) Test PSU SCB Study and Preliminary Results Industry Initiative Summary 3 Lab Scale Tests Monotonic Tests Indirect Tensile Semi Circular Beam Disk Shaped Compact Tension Cyclic Tests Four Point Bending Beam Indirect Tensile Uniaxial Push Pull Texas Overlay Picture Curtesy: IPC Global, Umass, Penn State 2

3 Lab Scale Tests (Cyclic Tests) Texas Overlay Tester Fatigue/Cantilever Trapezoid Bending Beam Model Scale Accelerated Tests Third Scale Model Mobil Load Simulator (MMLS3) 6 3

4 Test Tracks and Full Scale Tests and ALF, HVS, MLS,. Penn State Track NCAT Track Picture Curtesy: NCAT 7 Outline A Review of Asphalt Concrete Fatigue Tests Semi Circular Bend (SCB) Test PSU SCB Study and Preliminary Results Industry Initiative Summary 8 4

5 Background on SCB Early Work on Rocks (Chong and Kuruppu, 1984) Introducing SCB for Asphalt Testing (Molenaar, 2 & 22) Further Research (Mohammad et al., 24) LA Further Research IFIT(Alqadi et al., 215) IL Implementation in Specs (Mohammad et al., LTRC, 216) 9 SCB Test Apply on Rocks (Initial Application) Photo Source: Lim et al

6 SCB Test Applied to Rocks SCB Testing of Granite Rock Photo Source: Dynamic Behavior of Materials, Vol.1 11 SCB Test Applied to Rocks Compression Induced Fracture Surfaces and Failure Mechanism Photo Source: Advances in Materials Science and Engineering Vol. 214, Article

7 SCB Test Setup Applied Load Notch Support 12 mm 15 mm Support Specimen Thickness: 5 mm Notch Depth: 15 mm Notch Width: 1.5 mm 13 Parameters Used For Evaluation 5 Load (N) % Peak Load Work of Fracture (W ) Peak Load (P ) Inflation Point (m) Critical Displacement Displacement (mm) Fracture Energy G W B L B: Specimen Thickness L: Ligament Length Flexibility Index G FI A abs m A: Constant Stiffness Index 5% Peak Load in Pre Peak Curve 14 7

8 Louisiana SCB Method (J Integral Concept) Notch Depth: 25.4 mm Notch Depth: 31.8 mm Notch Depth: 38. mm Strain Energy to Failure Plot Source: Mohammad et al Louisiana SCB Method (J Integral Concept) 1 1 Where: = Critical strain energy release rate, KJ/m 2 ; b = Specimen thickness, m; a = Notch depth, m; and U = Strain energy to failure, kn m or KJ. thickness: 5 mm multiple notch depths (25.4/31.8/38 mm) Plot Source: Elseifi et al. 212 : slope of the notch depth vs. strain energy plot 16 8

9 Advantages of SCB Test Specimen Easily Prepared Using SGC or Field Cores Four Specimens from One Compacted Mix Easy to Perform and Simple to Analyze Possible To Perform Test Using Marshall Type Stability Tester Good Correlation to Field Performance?? 17 Current Issues What Test Parameters to Use? What test temperature? How fast to test? What pass/fail criteria? Sensitivity to Mix Parameters Short term aged or long term aged mix? Test repeatability and reproducibility? 18 9

10 Outline A Review of Asphalt Concrete Fatigue Tests Semi Circular Bend (SCB) Test PSU SCB Study and Preliminary Results Industry Initiative Summary 19 INVESTIGATE Effect of Test Temperature Effect of Loading Rate Range Effect of Aging (short term vs long term) Effect of Binder Content and Binder Stiffness Effect of Voids 2 1

11 Test Temperature I FIT Protocol: Fixed Temperature for All Mixes, i.e. 25 Proposed Protocol: Using Effective Temperature Concept NCHRP 74: A Performance Related Specification for HMA Harrisburgh is around 18 Freq: Loading Frequency, Hz; MAAT: Mean Annual Air Temperature, ; MAAT: Standard Deviation of the Mean Monthly Air Temperature; Rain: Annual Cumulative Rainfall Depth, inches; Sunshine: Mean Annual Percentage Sunshine, %; and Wind: Mean Annual Wind Speed, Mph. 21 Test Loading Rate Current Protocol: 5 mm/min (too fast, not enough data points, higher COV).5 mm/min (too slow, affected by creep) Findings: Loading rate between 5 to 2 mm/min will minimize the effect of creep, and provide a reasonable range for FI for long term aged mix

12 Specimen Preparation SGC Specimen or Field Cores Cut to Ensure Minimum AV Gradient Obtain Density Condition Specimens at Test Temperature Conduct Test 15 mm 2 mm 5 mm 5 mm It Takes 3 days from Mixing to Obtain Results 15 mm 2 mm 23 Specimens After Cutting Ready for Testing Specimens Before (L) / After (R) Testing 24 12

13 35 3 Typical Load vs Displacement Curves 3 Replicates, PG 58 28, 25 C 5 mm/min 25 Load (N) mm/min 5 mm/min 1 mm/min Displacement (mm) 25 Temperature/Loading Rate Effects Fracture Energy (J/m^2) Virgin Agg+PG58+7AV Virgin Agg+PG58+4AV Fracture Energy Comparison 1 mm/min 5 mm/min 2 mm/min 5 mm/min Virgin Agg+PG58+7AV+5.9BC Virgin Agg+PG76+7AV 18 Virgin 18C Virgin 18C Virgin 18 C Virgin 18C 26 13

14 Temperature/Loading Rate Effects Flexibility Index Flexibility Index Comparison 1 mm/min 5 mm/min 2 mm/min 5 mm/min 18 Virgin Agg+PG58+7AV Virgin Agg+PG58+4AV Virgin Agg+PG58+7AV+5.9BC Virgin Agg+PG76+7AV Virgin 18C Virgin 18C Virgin 18 C Virgin 18C 27 Stiffness Indices of Aged Mixes 15 Stiffness Index 12 Long Term Aged, SI Line of Equality y = x R² = Short Term Aged, SI 28 14

15 Facture Energy of Aged Mixes 45 Fracture Energy 4 Long Term Aged Fracture Energy (J/m^2) y =.663x R² = Short Term Aged Fracture Energy (J/m^2) 29 FI of Aged Mixes Flexibility Index 1 mm/min 5 mm/min 2 mm/min 5 mm/min Long Term Aged Flexibility Index Short Tem Aged Flexibility Index 3 15

16 Temperature/Loading Rate Sweep in SCB 2 Flexibility Index Long Term Aged Flexibility Index Faster Loading 1 mm/min 5 mm/min 2 mm/min 5 mm/min Temperature ( ) 31 Effect of Binder Content 3 STOA, PG64 22, 7% AV Load (N) Post Peak Slope 4.7% BC 5.2% BC 5.7% BC 6.2% BC Displacement (mm) 32 16

17 Effect of Binder Content 6 7% Air Void Flexibility Index PG58 28 PG64 22 PG Binder Content (%) 33 Effect of Binder Content 35 4% Air Void 3 Flexibility Index Binder Content (%) PG58 28 PG64 22 PG

18 Effect of Binder Grade (Stiffness) 3 STOA, 7% AV, 5.2% BC Load (N) PG58 28 PG64 22 PG Displacement (mm) 35 Effect of Binder Grade (Stiffness) 6 7% Air Void 5 Flexibility Index % BC 5.2% BC 5.7% BC 6.2% BC Binder High Temperature Grade 36 18

19 Effect of Air Void Load (N) Typical Load vs. Displacement Curve STOA, PG64 22, 5.2% BC 2% AV 4% AV 7% AV Displacement (mm) 37 Effect of Air Void Flexibility Index % Binder Content PG58 28 PG64 22 PG Air Void (%) 38 19

20 The Effect of Air Void Reported by UIUC Source: Maxwell The Effect of Air Void Reported by UIUC Source: Maxwell

21 CRM Mixes Peak Load (LTOA) 41 CRM Mixes Fracture Energy (LTOA) Fracture Energy (J/m 2 ) PG64+22 PG % CRM 42 21

22 CRM Mixes Flexibility Index (LTOA) Flexibility Index PG64+22 PG % CRM 43 Outline A Review of Asphalt Concrete Fatigue Tests Semi Circular Bend (SCB) Test PSU SCB Study and Preliminary Results Industry Initiative Summary 44 22

23 How Did it Start? Move to Performance Testing Initiated by Asphalt Quality Improvement Committee and PAPA Industry Expressing Interest in Participating 45 Purpose of the Effort Bridge the Gap to Performance Testing Investigate Performance of PA Mixes in SCB Develop A Database of SCB Test Results Evaluate Sensitivity of the PA Mixes to the Test Evaluate Correlation with Field Performance 46 23

24 Mix Criteria and Variables Air Void: 5.5% (Final SCB Specimen) Design Binder Content (and +.5%) Mixes with 15% RAP at Design BC and at.5% Higher Binder Content Mixes at higher RAP Contents NMAS: 4.75, 9.5mm, 12.5mm, 19mm, 25mm 47 Plant vs Lab, and Aging Effect Lab Prepared Mix Short Term Aged 275F) Long Term Aged (5 185F) Plant Prepared Mix Short Term Aged Long Term Aged 48 24

25 What Do We Do with the Plugs? Once Received at NECEPT, Enter into Database: Identification Code Source Date of Compaction Date of Receipt at NECEPT Lab vs Plant Mix Aging Condition Air Void 49 Current Status (as of 1/15/18) # of producers, 7 # of plugs, 41 of Plant Mixes, 2 of Lab Mixes, 2 AS (4.75, 9.5, 19, rcents (, 1, 15, of SCB Tests,

26 Current Status (As of 1/15/18) # of plugs from producers varies: 1, 2, 3, 4, 1, 16 All with PG First Plug received: 11/28/217 Latest Plug received: 1/1/ Processing/Testing Specimens Photos Specific Gravity Measurement Cut into 4 Specimens Specific Gravity Measurement Conduct SCB 52 26

27 Industry SCB Test Results Repeatability of Industry SCB Specimens Load, N Displacement, mm 53 Industry SCB Test Results 35 Mix Source A: Plant mix, NMAS 9.5mm, PG64 22, 4.5% AV. Fracture Energy, J/m^ STOA, 5.6%BC LTOA, 5.6%BC STOA, 6.1%BC LTOA, 6.1%BC 54 27

28 Industry SCB Test Results Mix Source A: Plant mix, NMAS 9.5mm, PG64 22, 4.5% AV. Peak Load (N) STOA, 5.6%BC LTOA, 5.6%BC STOA, 6.1%BC LTOA, 6.1%BC 55 Industry SCB Test Results 25 Mix Source A: Plant mix, NMAS 9.5mm, PG64 22, 4.5% AV. Flexibility Index STOA, 5.6%BC LTOA, 5.6%BC STOA, 6.1%BC LTOA, 6.1%BC 56 28

29 Waiting for More Specimens Continue Receiving Material Continue Cataloging/Testing Materials Continue Analysis PLEASE: Label Materials Properly Ship/Transport Safely Include Mix Information/JMF/Compaction Date 57 Outline A Review of Asphalt Concrete Fatigue Tests Semi Circular Bend (SCB) Test PSU SCB Study and Preliminary Results Industry Initiative Summary 58 29

30 Summary Higher loading rate Lower FI Higher temperature Higher FI Higher Binder Content Higher FI Higher Air Void Higher FI? Higher Aging Lower FI Increase in Binder Stiffness (Grade)? CRM+PG 58 higher FI compared with PG THANK YOU! 3