47 th Annual Mid Atlantic Quality Assurance Workshop February 4 th to 6 th, 2014 Atlantic City, NJ

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1 47 th Annual Mid Atlantic Quality Assurance Workshop February 4 th to 6 th, 2014 Atlantic City, NJ

2 Frank Fee & Ron Corun, NuStar Asphalt The Credit or Blame Wayne Byard/Mike Jopko, Trap Rock Industries The Guinea Pig Supplier NJDOT Materials and Pavement Design Bureau s

3 Due to high asphalt contents, a potential for draindown of binder exists Defined as liquid binder running off aggregate surface Results in fat spots and segregated areas of heavy and low binder content

4 To help reduce the potential of draindown, polymermodified asphalt (PMA) and fibers used with SMA and OGFC PMA results in better adhesion to aggregate at higher temps than Neat binders (generally higher viscosity) Fibers increase stiffness of mastic by increasing surface area Neat PMA PMA + Fibers

5 Cost fibers and rental equipment Fibers need to be separated or fluffed prior to addition or clumping can occur Metering required and should have sight glass to ensure fibers flowing Fibers must be included in ignition furnace calibration impossible to separate AC and Fiber changes during production

6 Found in pavement surface Other areas had little to no fibers Possibly due to the feeding system Guy throwing in bags at batch plant

7 The inclusion of fibers used to increase the viscosity of the mastic (binder, fines, fibers) Increased mastic viscosity will stick to aggregate better and resist draindown Utilizing an asphalt binder with higher viscosity can help increase mastic viscosity As temperature decreases, binder viscosity increases Reduction in mixture temp will create compaction issues Must couple mixture temp reduction with WMA additive WMA technology that does not influence binder viscosity

8 General methodology Utilize existing SMA design as your starting point (i.e. asphalt content, aggregate blend) Determine Draindown (AASHTO T305) and compacted air voids after reducing mixture temperature Example: 325, 300, 280, 255 o F Compare draindown and compacted air voids Examine mixing process to ensure coating is taking place Make slight mixture adjustments if necessary

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10 First project to look at fiberless SMA with WMA Location: Rt 1 in New Jersey 12.5mm SMA 6.4% AC content PG % cellulose fibers Washed Gradation Screen % Pass ½ ¾ ½ / # # # st Project Supplier did own assessment of compacted air voids

11 Mixture ID Temperature (F) Percent Mixing Testing Draindown Normal SMA WMA SMA #1 (No Fibers) WMA SMA #2 (No Fibers) WMA SMA #3 (No Fibers)

12 Field Core Density Normal SMA Density = 5.13% air voids Produced over 315F WMA SMA Density = 5.12% air voids Produced under 280F

13 10,000,000 1,000,000 Dynamic Modulus (psi) 100,000 10,000 1,000 SMA - Normal Production 100 SMA - WMA with No Fibers 1.0E E E E E E E E+07 Loading Frequency (Hz)

14 Vertical Deformation (mm) Loading Cycles (n) 0 2,500 5,000 7,500 10,000 12,500 15,000 17,500 20,000 SMA - Normal Production SMA - WMA & No Fibers Cycles to 12.5mm Rutting = > 20,000 cycles

15 SMA - WMA with No Fibers Sample ID Temp (F) Displacement Fatigue Life (inches) (cycles) # 1 10,472 # 2 77 F 0.025" 27,855 # 3 16,255 Average (Trimmed Mean) = 18,194 SMA - Normal Production Sample ID Temp (F) Displacement Fatigue Life (inches) (cycles) # 1 2,126 # 2 77 F 0.025" 2,425 # 3 1,458 Average (Trimmed Mean) = 2,003

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19 For initial pilot, reduction in production temp successfully reduced draindown when fibers eliminated 275 to 285 o F 270 to 280 o F Field densities of with and without fibers statistically equal Mixture performance looked good Lower production temps not aging binder as normal Stiffness slightly lower Large increase in fatigue resistance (higher effective AC?) One Complaint!

20 Supplier conducted draindown and compaction on own Provided Rutgers loose mix to evaluate/compare general performance properties Mixture Stiffness Dynamic Modulus (E*) Rutting Resistance Asphalt Pavement Analyzer Fatigue Resistance Overlay Tester

21 10,000,000 Dynamic Modulus (psi) 1,000, ,000 10,000 WMA SMA SMA 1, E E E E E E E E+07 Loading Frequency (Hz)

22 64 o C Test Temp.; 100psi Hose Pressure; 100 lb Load Load APA Rutting (mm) APA 8,000 Cycles SMA = 2.43 mm (Std Dev = 0.26 mm) SMA = 3.01 mm (Std Dev = 0.10 mm) 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 Number of Loading Cycles

23 WMA SMA SMA Overlay Tester Fatigue Life (cycles)

24 Mixture performance between SMA and WMA SMA similar Increased production temps results in slightly stiffer mixture Eliminating fibers and reducing temps results in superior fatigue resistance Properly designed SMA with PMA and stone onstone contact (assuming quality stone) should not rut

25 Determine Optimal Temperature for WMA SMA 12.5 mm NMAS SMA 6.5% Asphalt Content PG % Cellulose Fibers 0.04% Draindown at Design Washed Gradation Screen % Pass ½ ¾ ½ / # # # # # # #

26 Draindown (%) Air Voids (%) Draindown (%) Compacted Air Voids (%) Temperature ( o F)

27 Final Result Optimal temp range for mixture between 265 and 255 o F. In that range; Air voids slightly above 4% Draindown around 0.2 to 0.25% (specification is 0.3%) Dust to Effective Binder below allowable Final Recommendation Maintain asphalt content and increase dust content Increase dust will help close up air voids and reduce draindown Received phone call from contractor saying project went great and they are planning to bid all future SMA projects the same way

28 Determine Optimal Temperature Range 12.5mm NMAS SMA 6.7% Total Asphalt Content PG % RAP 0.4% Total Binder Weight Contribution 0.3% Cellulose Fibers Washed Gradation Screen % Pass ½ ¾ ½ / # # # # # # #

29 % Total Asphalt Content (6.3% Virgin Binder) (Baseline Mix with Fibers: 325 o F; 0.14% Draindown; 4.4% Compacted Air Voids) Compacted Air Voids Draindown High Draindown created issues with compaction Compacted Air Voids (%) Draindown (%) Mix Temperature ( o F)

30 1 st Trial Results Testing showed that air voids were slightly low and Draindown was still above specification For this particular mix, the elimination of fibers is creating an slightly over asphalted mix For Trial #2, asphalt content was reduced 0.3% and testing was again conducted

31 % Total Asphalt Content (6.0% Virgin Binder Content) (Baseline Mix with Fibers: 325 o F; 0.10% Draindown; 4.7% Compacted Air Voids) Compacted Air Voids (%) Draindown Compacted Air Voids (%) Draindown (%) Mix Temperature ( o F)

32 For the Virginia SMA, eliminating fibers created an over asphalted condition Fibers creating surface area taking up additional asphalt 2 nd trial showed a reduction of 0.3% asphalt was required to maintain draindown Supplier also slightly increased dust to help tighten up air voids

33 Traditionally fibers used to stiffen mastic of SMA mixtures Can be accomplished by increasing the viscosity of the binder within the mastic WMA technologies that do not affect binder viscosity can be used to reduce temperature (increasing viscosity) while acting as a compaction aid Mixture performance equivalent SMA slightly stiffer WMA SMA far superior fatigue From experience gained, not all mixtures react the same and each need to be evaluated separately

34 CAIT RUTGERS Thomas Bennert, Ph.D. Rutgers University