Visco-Elastic Determination of Laboratory Mix & Compaction Temperatures

Transcription

1 Visco-Elastic Determination of Laboratory Mix & Compaction Temperatures Excerpts from NCHRP 9-39 research for discussion John Casola, Malvern Instruments & Randy West, NCAT

2 Outline Introduction Review NCHRP 3-39 goals Concept of the approach to determine Mix & Compaction Temperatures Review some of the data Compare predicted results with mix results

3 Why a new method? Equi-viscous method to determine Mix & Compaction temperatures has been used for many years and works well with neat, unmodified asphalt binders.

4 Why a new method? Equi-viscous method to determine Mix & Compaction temperatures has been used for many years and works well with neat, unmodified asphalt binders. However, engineered binders which are modified are not as easy to predict with this method.

5 Why a new method? Equi-viscous method to determine Mix & Compaction temperatures has been used for many years and works well with neat, unmodified asphalt binders. However, engineered binders which are modified are not as easy to predict with this method. In fact, using the equi-viscous method generally over predicts the temperatures which would cause over heating of the liquid asphalt binder, destroying the beneficial properties of the modifier.

6 Equi-Viscous Method (rotational viscosity or Brookfield test) Viscosity, Pa s Compaction Range Mixing Range Temperature, C

7 Modified have significantly different temperature susceptibility Viscosity, Pa s Neat Compaction Range Mixing Range Modified Temperature, C

8 Research Approach for 9-39 Evaluate several binder properties using most promising techniques. Determine temperature limits that cause binder degradation and emissions problems. Use mix tests to validate mixing and compaction temperatures. Use test of reasonableness to recommend the best procedure.

9 Candidate Methods for Determining Mixing & Compaction Temperatures High Shear Rate Viscosity (Yildirim, U/Texas) Steady Shear Flow (Reinke, MTE) Dynamic Shear Rheology (Casola, Malvern)

10 NCHRP 9-39 Work Plan 14 Asphalt Binders Part 1: Binder Testing Part 2: Mix Testing Steady Shear Flow Correlations Determine Minimum Mixing Temps Mix Coating Rotational Viscosity Determine Intermediate Mix Handling Temps Mix Workability Dynamic Shear Rheology & Reasonableness Determine Compaction Temps Range Mix Compaction Smoke & Emissions Potential Test Grade Binders Before & After SEP Establish Max Temp to Avoid Emissions Establish Max Temp to Avoid Degradation Check for Excessive Temps Determine Effect of Temps on Mix Props IDT Creep & Strength Test Select Best Method Mix Coating 4 Asphalt Binders Validation of Method Mix Workability Mix Compaction Draft New Test Method for Establishing Mixing & Compaction Temperatures

11 Work Plan Involved 14 Binders 14 Asphalt Binders Part 1: Binder Testing Part 2: Mix Testing Steady Shear Flow Correlations Determine Minimum Mixing Temps Mix Coating Rotational Viscosity Determine Intermediate Mix Handling Temps Mix Workability Dynamic Shear Rheology & Reasonableness Determine Compaction Temps Range Mix Compaction Smoke & Emissions Potential Test Grade Binders Before & After SEP Establish Max Temp to Avoid Emissions Establish Max Temp to Avoid Degradation Check for Excessive Temps Determine Effect of Temps on Mix Props IDT Creep & Strength Test Select Best Method Mix Coating 4 Asphalt Binders Validation of Method Mix Workability Mix Compaction Draft New Test Method for Establishing Mixing & Compaction Temperatures

12 Both Mix Testing & Binder Testing 14 Asphalt Binders Part 1: Binder Testing Part 2: Mix Testing Steady Shear Flow Correlations Determine Minimum Mixing Temps Mix Coating Rotational Viscosity Determine Intermediate Mix Handling Temps Mix Workability Dynamic Shear Rheology & Reasonableness Determine Compaction Temps Range Mix Compaction Smoke & Emissions Potential Test Grade Binders Before & After SEP Establish Max Temp to Avoid Emissions Establish Max Temp to Avoid Degradation Check for Excessive Temps Determine Effect of Temps on Mix Props IDT Creep & Strength Test Select Best Method Mix Coating 4 Asphalt Binders Validation of Method Mix Workability Mix Compaction Draft New Test Method for Establishing Mixing & Compaction Temperatures

13 Correlate the Mix & Binder Results 14 Asphalt Binders Part 1: Binder Testing Part 2: Mix Testing Steady Shear Flow Correlations Determine Minimum Mixing Temps Mix Coating Rotational Viscosity Determine Intermediate Mix Handling Temps Mix Workability Dynamic Shear Rheology & Reasonableness Determine Compaction Temps Range Mix Compaction Smoke & Emissions Potential Test Grade Binders Before & After SEP Establish Max Temp to Avoid Emissions Establish Max Temp to Avoid Degradation Check for Excessive Temps Determine Effect of Temps on Mix Props IDT Creep & Strength Test Select Best Method Mix Coating 4 Asphalt Binders Validation of Method Mix Workability Mix Compaction Draft New Test Method for Establishing Mixing & Compaction Temperatures

14 Ensure Temperatures are in Range 14 Asphalt Binders Part 1: Binder Testing Part 2: Mix Testing Steady Shear Flow Correlations Determine Minimum Mixing Temps Mix Coating Rotational Viscosity Determine Intermediate Mix Handling Temps Mix Workability Dynamic Shear Rheology & Reasonableness Determine Compaction Temps Range Mix Compaction Smoke & Emissions Potential Test Grade Binders Before & After SEP Establish Max Temp to Avoid Emissions Establish Max Temp to Avoid Degradation Check for Excessive Temps Determine Effect of Temps on Mix Props IDT Creep & Strength Test Select Best Method Mix Coating 4 Asphalt Binders Validation of Method Mix Workability Mix Compaction Draft New Test Method for Establishing Mixing & Compaction Temperatures

15 Determine the Best Method 14 Asphalt Binders Part 1: Binder Testing Part 2: Mix Testing Steady Shear Flow Correlations Determine Minimum Mixing Temps Mix Coating Rotational Viscosity Determine Intermediate Mix Handling Temps Mix Workability Dynamic Shear Rheology & Reasonableness Determine Compaction Temps Range Mix Compaction Smoke & Emissions Potential Test Grade Binders Before & After SEP Establish Max Temp to Avoid Emissions Establish Max Temp to Avoid Degradation Check for Excessive Temps Determine Effect of Temps on Mix Props IDT Creep & Strength Test Select Best Method Mix Coating 4 Asphalt Binders Validation of Method Mix Workability Mix Compaction Draft New Test Method for Establishing Mixing & Compaction Temperatures

16 Draft a Procedure 14 Asphalt Binders Part 1: Binder Testing Part 2: Mix Testing Steady Shear Flow Correlations Determine Minimum Mixing Temps Mix Coating Rotational Viscosity Determine Intermediate Mix Handling Temps Mix Workability Dynamic Shear Rheology & Reasonableness Determine Compaction Temps Range Mix Compaction Smoke & Emissions Potential Test Grade Binders Before & After SEP Establish Max Temp to Avoid Emissions Establish Max Temp to Avoid Degradation Check for Excessive Temps Determine Effect of Temps on Mix Props IDT Creep & Strength Test Select Best Method Mix Coating 4 Asphalt Binders Validation of Method Mix Workability Mix Compaction Draft New Test Method for Establishing Mixing & Compaction Temperatures

17 This discussion will focus on DSR method 14 Asphalt Binders Part 1: Binder Testing Part 2: Mix Testing Steady Shear Flow Correlations Determine Minimum Mixing Temps Mix Coating Rotational Viscosity Determine Intermediate Mix Handling Temps Mix Workability Dynamic Shear Rheology & Reasonableness Determine Compaction Temps Range Mix Compaction Smoke & Emissions Potential Test Grade Binders Before & After SEP Establish Max Temp to Avoid Emissions Establish Max Temp to Avoid Degradation Check for Excessive Temps Determine Effect of Temps on Mix Props IDT Creep & Strength Test Select Best Method Mix Coating 4 Asphalt Binders Validation of Method Mix Workability Mix Compaction Draft New Test Method for Establishing Mixing & Compaction Temperatures

18 Binders In the Test Plan K -16 J -22 F G,H,L M, N -28 D O I -34 A E C -40 B unmodified grade modified grade

19 Binders In the Test Plan Binder I.D. Binder Grade Modification Suppliers Mixing Temp, ( F) Suppliers Compaction Temp. ( F) B PG SBS C PG SBS D PG None E PG Air Blown F PG None G PG SBS+PPA H PG SBS I PG Air Blown J PG None K PG None L PG Crumb Rubber M PG F-T Wax+SBS No information available N PG SBS No information available O PG None

20 Asphalts Tested Spec Grade TruGrade Supplier Freq at 86 A PG None Husky B PG SBS Husky 1.1 C PG SBS Husky D PG None Husky E PG Air Blown Husky F PG None Ergon 75 G PG SBS + PPA Ergon 0.03 H PG SBS Citgo I PG Elvaloy Air Blown + PPA Citgo J PG None Alon K PG None Alon-Apart? 800 L PG Crumb Rubber + SBS Apart M PG Sasoflex Sasol N PG SBS Valero O PG None Citgo P PG SBS + Sasoflex Sasoflex 0.23 W PG Air Blown Modified Husky X PG Elvaloy Un-Modified Ergon Y PG None Citgo Z PG SBS + Air Blown Alon

21 Concept Use of Visco-Elastic criteria for the ranking & determination of laboratory mix & compaction temperatures. Identify a range of temperatures Compile a Master Curve via TTS Identify a threshold for comparison A clear point where the material is no longer Newtonian Frequency where the Phase angle equals 86 o Correlate to actual Lab Mix performance Compare to Manufactures recommendations Compare to EC-101

22 Some Background On Why This Approach Mixing stresses & shear rates are extremely complex. The ability to coat & compact differ from Neat to Modified binders. Elastic contributions are significantly different in modified binders which is the likely cause of these differences. The transition from Newtonian to non-newtonian behavior would make for an easily identifiable threshold. We are unable to clearly see these differences at or around the mixing temperature. In order to quantify visco-elastic differences the sample temperature must be lowered. Simply put, a phase angle above 86 o is considered in the Newtonian region. A Phase Angle of 86 o is an easily identifiable transition point of the material exhibiting VE behavior for comparison. To see this transition over a reasonable range of frequency, we will investigate the samples at a temperature of 80 o C

23 Dynamic Shear Rheology Comparing 2 Binders; Neat vs. Modified Neat Modified Rad/s

24 Sample A Frequency Sweeps at Several Temperatures

25 Asphalt A Time Temperature Superposition to 80 o C

26 Sample A Identify Freq at Phase of 86 o at a Temperature of 80 o C Freq = rad/sec Phase = o Temp = 80 o C

27 Comparison of TruGrade vs. DSR Modified Un-Modified Spec Grade TruGrade Spec Grade Freq at 86 Mix T (F) M PG G PG SBS + PPA 324 G PG M PG Sasoflex 319 H PG C PG SBS 315 C PG H PG SBS 314 I PG B PG SBS 309 B PG I PG Air Blown 306 F PG O PG None 301 O PG E PG Air Blown 300 K PG F PG None 298 J PG D PG None 296 E PG J PG None 293 D PG K PG None 292

28 Mix Testing Performed by NCAT

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31 Estimated Mix Temperature Chart Estimated Mix Temperature 1000 Frequency (rad/sec) Temperature (F)

32 Model the relationship Mixing Temperature (ºF) = 325ω (ºC) = 163ω Compaction Temperature (ºF) = 300ω (ºC) = 149ω where ω is the frequency in rad/s where the measured phase angle equals 86 o at a temperature of 80 o C

33 Predicted Mix & Compaction Temperatures

34 EC-101 Recommendations EC-101 Recomendations 340 Mix Temperature Min EC101 Max EC101 Midpoint EC101 Poly. (Midpoint EC101) Grade

35 Comparison to Manufacturer s Recommendations Predicted vs. Mfg 350 Temperature (F) Series1 Series2 Series3 B C D E F G H I J K O Sample

36 Summary of Results Compare to Equi-Viscous Method

37 Summary of Results Compare to Mix & Compaction Results

38 Summary of Results Compare to Mix & Compaction Results M M M c c C

39 Regarding the Comparison to Industry Guidelines Everything fell within the EC-101 Guidelines. Not a very useful method for first approximation Most of the predicted mix temperatures fell within the Manufacturer s guidelines which, are a much narrower temperature range to that of EC-101. Of those that fell outside of the Mfg s guidelines: all predicted temperatures were lower.

40 In Summary Initial review appears to rank and predict within reason. Some of the samples were predicted to be lower than the Mfg s recommendations. Conclusion of the project is nearing with a formal report to follow. Testing is quick & easy

41 Thank you for your time Questions!