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1 Pavement Design and Materials Research Update Western Regional Superpave Center (WRSC) Pavements/Materials Engineering Program Dept. of Civil & Env. Engineering University of Nevada ; Slide No. 1

2 Presentation Outline Evaluation of Warm Mix Asphalt Concrete Pavement in South Dakota Conditions (SDDOT). Evaluation of WMA Technologies for Use in Modified Asphalt Mixtures (ALON Asphalt Company). Evaluation of WMA with RAP Mixtures (NDOT, Washoe RTC). Laboratory Evaluation of Thin Asphalt Overlays for Nevada. (USDOT/NDOT). ; Slide No. 2

3 LABORATORY EVALUATION OF THIN ASPHALT OVERLAYS FOR NEVADA (USDOT / NDOT) ; Slide No. 3

4 Introduction States and agencies survey responses 3% 11% more then 2 in. between 1.5 in. and 2 in. less than 1.5 in. 86% Summary is based on data from NCHRP synthesis 464: Thin Asphalt Overlays ; Slide No. 4

5 Introduction (Cont d) Asphalt Overlay Characteristics Functional Characteristics Structural Characteristics Service Life Ride Quality Improvement. Skid Resistance Improvement. Noise Level Reduction. Save the Existing Pavement Structure. Structural Strength Increase. Fatigue Life Increase. Longest average service life (7 to 11 years) among the preventive maintenance treatments. ; Slide No. 5

6 Overall Research Objective Assess the use of thin asphalt overlays in Nevada. Two aggregate sources: North (Lockwood) and South (Lone Mountain). Conduct mix designs using NDOT Hveem design method. Evaluate the performance properties of the designed mixtures. ; Slide No. 6

7 Experimental Plan Northern Nevada Aggregate: Lockwood (12.5 mm) Binder: PG 64-28NV HVEEM Mix Design Southern Nevada Aggregate: Lone Mountain (9.5 mm) Binder: PG 76-22NV 6.3 % OBC +/- 0.4% (N) Optimum Binder Content (OBC) Based on Volumetric Properties 4.5% OBC +/- 0.3% (S) Performance Tests Raveling Test Resistance to surface raveling (unconditioned & after 3 F-T cycles) Cantabro Loss Test Resistance to surface abrasion Dynamic Modulus Mechanical Property Flow Number Resistance to Rutting Texas Overlay Tester Resistance to reflective cracking LISST Bond Test Interlayer shear bond strength Revise OBC Selection Based on Performance Properties ; Slide No. 7

8 Aggregate Gradation Sieve Size 19 mm 12.5 mm 9.5 mm 4.75 mm 2.36 mm 2.0 mm 1.18 mm mm 0.30 mm mm Percent Passing (NDOT 2014) mm No mm No mm No mm No mm No mm No mm No mm No mm No mm 3/8 inch 12.5 mm 1/2 inch 19.0 mm 3/4 inch 25.0 mm 1 inch 37.5 mm 1 1/2 inch Percent Passing Aggregate: Lone Mountain ½ AGG : 47% Crushed Fines: 38% Rinker Sand : 15% mm No mm No mm No mm No mm No mm No mm No mm No mm No mm 3/8 inch 12.5 mm 1/2 inch 19.0 mm 3/4 inch 25.0 mm 1 inch 37.5 mm 1 1/2 inch Aggregate: Lockwood ¾ AGG : 8% ½ AGG : 14% 3/8 AGG : 27% Crushed Fines: 33% Natural Fines : 18% Sieve Size (0.45 Power) Sieve Size (0.45 Power) ; Slide No. 8 Percent Passing

9 Tensile Strength at OBC (Nev. T341) AV 8 0.5% Tensile Strength (psi) Min 65 psi Tensile Strength Ratio TSR (%) 0 Lockwood Lone Mountain 0 Unconditioned Tensile Strength (psi) Moisture-Conditioned Tensile Strength (psi) Tensile Strength Ratio (%) ; Slide No. 9

10 Resistance to Raveling (ASTM D7196) Samples Preparation Target Height: 70 ± 5 mm Number of Gyrations: 20 Test Duration: 15 min/sample Percent of mass loss by Surface Raveling at 77 F (25 C) F-T 3 F-T 0 F-T 3 F-T L6428 mixture LM7622 mixture OBC- OBC OBC+ ; Slide No. 10

11 Resistance to Surface Abrasion (Cantabro Loss) Samples Preparation (Tex-245-F) Target Height: 115 ± 5mm Target Density: 93 ± 1% Northern Mix (Lockwood) Southern Mix (Lone Mountain) Cantabro Loss (%) OC % OC OC % Binder content by DWA (%) Cantabro Loss (%) 22 OC % OC OC % Binder Content by DWA ; Slide No. 11

12 Dynamic Modulus Master Curves Northern Mix (Lockwood) Southern Mix (Lone Mountain) E* at 68 F, ksi 100 E* at 68 F, ksi E-06 1.E-04 1.E-02 1.E+00 1.E+02 1.E E-06 1.E-04 1.E-02 1.E+00 1.E+02 1.E+04 Reduced Frequency, Hz AC 5.9% AC 6.3% AC 6.7% Reduced Frequency, Hz 4.20% 4.50% 4.80% ; Slide No. 12

13 Resistance to Rutting FN test conditions (NCHRP 09-33): (1) unconfined; (2) 87 psi (600 kpa) deviator stress; (3) and at 7-day maximum pavement temperature 1 inch below the pavement surface, at 50% reliability. Unconfined Flow Number L6428 mixtures [Tested at 129 F (54 C)] LM7622 mixtures [Tested at 147 F (64 C)] OBC- OBC OBC+ > 30 MESALs 10 to < 30 MESALs 3 to <10 MESALs ; Slide No. 13

14 Resistance to Reflective Cracking Samples Preparation (TTI OT): Standard: Tex-248-F Target Density: 93 ± 1% Aging: Short-term Conditioning Testing Temperature: 50 ºF (10 ºC) Percent drop in initial load after 5,000 loading cycles L6428 mixtures LM7622 mixtures OBC - OBC OBC+ ; Slide No. 14

15 Interlayer Bond Strength (LISST Draft AASHTO) Interlayer Shear Strength (ISS), psi No Tack Coat Slow Setting SS (50% diluted) High Performance Seal HPS L6428 mixtures LM7622 mixtures ; Slide No. 15

16 Overall Summary High Resistance to Surface Raveling. High Resistance to Surface Abrasion. Good stiffness property. Acceptable rutting resistance High Resistance to Reflective Cracking. ; Slide No. 16

17 Thank You! ; Slide No. 17