Rubberized Asphalt Concrete Center (RACTC)

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USE OF ASPHALT RUBBER IN PAVEMENTS
Construction Inspection Overview
Technology Transfer Series ARHM- 105 Webinar
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PRESENTATION TOPICS

• CONSTRUCTION INSPECTOR ROLES
• COMPOSITION OF ARHM
• MIX DESIGN CERTIFICATES
• INSPECTION AT THE PLANT
• JOB SITE INSPECTIONS
• TROUBLESHOOTING SUMMARY

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CONSTRUCTION INSPECTOR ROLES
Serve as link between the designer and the
contractor Verify that work conforms to plans
and specifications
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COMPOSITION OF ARHM
1. Gap Graded Aggregate 2. Asphalt Rubber Binder
Previously AR-4000 Now
PG 58-22 or PG 64-16 Scrap Tire
75 High Natural Rubber 25
Paving Asphalt - 80
Crumb Rubber - 20
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AGGREGATE GRADATIONS
Sieve Size "C2"1/2" dense graded "C2"1/2" dense graded "ARHM-GG-C"1/2" gap-graded "ARHM-GG-C"1/2" gap-graded
Sieve Size Min. - Max. (Mid Pt) Min. - Max. (Mid Pt)
19.0 mm (3/4 in.) 100   100  
12.5 mm (1/2 in.) 95-100 (97.5) 90-100 (95.0)
9.5 mm (3/8 in.) 72-88 (80.0) 78-92 (85.0)
4.5 mm (No. 4) 46-60 (53.0) 28-42 (35.0)
2.36 mm (No. 8) 28-42 (35.0) 15-25 (20.0)
600 µm (No. 30) 15-27 (21.0) 5-15 (10.0)
300 µm (No. 50) 10-20 (15.0)    
75 µm (No. 200) 2-7 (4.5) 2-7 (4.5)
A gap-graded mix is defined as continuously
graded with 1 or 2 finer sizes missing
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CRM GRADATION REQUIREMENTS
Greenbook Table 203-11.2.3.1 (A) Greenbook Table 203-11.2.3.1 (A) Greenbook Table 203-11.2.3.1 (A)
Sieve Size Scrap Tire CRM Percent passing High Natural CRM Percent passing
2.36 mm (No. 8) 100 100
2.00 mm (No.10) 98-100 100
1.18 mm (No. 16) 45-75 95-100
600 µm (No. 30) 2-20 35-85
300 µm (No. 50) 0-6 10-30
150 µm (No. 100 0-2 0-4 
75 µm (No. 200) --- 0-1
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CRUMB RUBBER
SCRAP TIRE 1/16 /- in Size
HIGH NATURAL RUBBER 1/32 /- in Size
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MIX DESIGN CERTIFICATES

• Submitted by the Contractor

• Per Greenbook (203-11), or local
• specifications

• Hveem Method
• (Modified CA Test Method 367)

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PROPERTIES OF ARHM MIX DESIGN

• Air Voids 3 - 6 per Greenbook
• Suggest Maximum 5

• Voids in Mineral Aggregates VMA
• 18 Minimum to 23 Maximum

• Asphalt Rubber Binder Content
• Greenbook Minimum 7.5 Max 8.7

• Combined Aggregate Gradation

• Stability (23 Min.)

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GREENBOOK MIX DESIGN
TABLE 203-11.3 (A) REQUIREMENTS FOR ARHM-GG TABLE 203-11.3 (A) REQUIREMENTS FOR ARHM-GG TABLE 203-11.3 (A) REQUIREMENTS FOR ARHM-GG TABLE 203-11.3 (A) REQUIREMENTS FOR ARHM-GG
SIEVE SIZE CLASS CLASS CLASS
SIEVE SIZE ARHM-GG-BMin. - Max. ARHM-GG-CMin. - Max. ARHM-GG-DMin. - Max.
25 mm (1 in.) 100 - -
19.0 mm (3/4 in.) 90-100 100 -
12.5 mm (1/2 in.) - 90-100 100
9.5 mm (3/8 in.) 60-75 78-92 78-92
4.5 mm (No. 4) 28-42 28-42 28-42
2.36 mm (No. 8) 15-25 15-25 15-25
600 µm (No. 30) 5-15 5-15 5-15
75 µm (No. 200) 0-5 2-7 2-7
Asphalt Rubber Binder by Weight of Dry Aggregate 7.5-8.4 7.5-8.7 7.5-8.7
Air Voids Calif. Test 367 3-6 3-6 3-6
Stabilometer Value Min. Calif. Test 304 and 366 25 23 23
Voids in Mineral Agg. Percent Min. 18 18 18
Once the percent asphalt rubber binder is determined by the mix design, the production tolerance shall be 0.5 as determined by California Test Method 362, 379, or 382. Once the percent asphalt rubber binder is determined by the mix design, the production tolerance shall be 0.5 as determined by California Test Method 362, 379, or 382. Once the percent asphalt rubber binder is determined by the mix design, the production tolerance shall be 0.5 as determined by California Test Method 362, 379, or 382. Once the percent asphalt rubber binder is determined by the mix design, the production tolerance shall be 0.5 as determined by California Test Method 362, 379, or 382.
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HVEEM MIX DESIGN CRITERIA
Modified, Step 2 not used Caltrans Mods Pending
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INSPECTION AT THE PLANT

• 1. Scales
• 2. Combined Grading
• 3. Proportioning
• Crumb Rubber
• Paving Asphalt

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INSPECTION AT THE PLANT
INSPECTION AT THE PLANT
Plant operations during ARHM mix production are
essentially the same as for standard AC mix
production. CT 109 requirements apply.
Differences

• Production and monitoring of the asphalt
• rubber binder for wet process mixes
• Plant mixing temperatures of 300-330ºF
• may be slightly higher than usual

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CT 109 - PLANT CERTIFICATION
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SAMPLING COMBINED AGGREGATE
DRUM PLANT BELT SAMPLE
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MIXING OF PAVING ASPHALT AND CRM
BLENDER CONTROL PANEL
MIXING/ REACTION TANK
CRM PROPORTIONING 1. SCRAP TIRES (3 BAGS) 2.
HIGH NATURAL (1 BAG)
BLENDING PAVING ASPHALT CRM
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INSPECTION AT THE PLANT Continued

• Viscosity of asphalt rubber binder..

• Temperature of ARHM

• Samples of CRM, paving asphalt,
• asphalt rubber binder, aggregates, and ARHM

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INSPECTION AT THE PLANT Continued
Asphalt Rubber Binder Production

• Required Documentation
• Component identification and proportions
• CRM gradations
• AR test results showing compliance with
• specifications
• Asphalt Cement
• Asphalt Modifier (Extender Oil)
• Scrap Tire CRM
• High Natural CRM

AR Binder Design Profile
Certificates of Compliance
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AR BINDER PRODUCTION
Asphalt Rubber Binder Design Profile

TEST Minutes of Reaction Minutes of Reaction Minutes of Reaction Minutes of Reaction Minutes of Reaction Spec. Limits _at_ 45 minutes 2006 Greenbook
TEST 45 90 240 360 1,440 Spec. Limits _at_ 45 minutes 2006 Greenbook
Viscosity, Haake-Type _at_ 191ºC (375ºF) Centipoise 2400 2800 2800 2800 2100 1500 - 4000
Resilience_at_ 25ºC (77ºF) ( Rebound) (ASTM D 5329) 27 -- 33 -- 23 18 Minimum
R B Softening Pt., ºC (ºF) (ASTM D36) 59.0 59.5 59.5 60.0 58.5 52 74 (125-165ºF)
Cone Pen _at_ 25ºC (ASTM D217) 39 -- 46 -- 50 25 70
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AR BINDER PRODUCTION Continued
Inspection Items

• Batch sheets or production logs for AR binder
  that show the amounts (typically by mass) of the
  components used
• Asphalt Cement
• Extender oil
• Scrap tire CRM
• High natural CRM

Check Proportions
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AR BINDER PRODUCTION Continued
The AR binder production logs or viscosity
testing logs should show when the CRM was added.

Before adding AR Binder to the Aggregate
1. Verify minimum AR interaction time of 45
minutes has elapsed 2. Verify AR binder
viscosity meets or exceeds the minimum 1500 cPs
requirement at 375ºF 3. Continue to monitor
viscosity hourly during RAC mix production
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HAAKE FIELD VISCOSITY TEST
Haake Viscometer
1500 4000 Centipoise at 375oF
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AR BINDER PRODUCTION Continued

• Follow sampling and testing frequency
  requirements listed in the specifications for AR
  binder and individual components.
• Typically, at least one one-gallon sample
• should be obtained from each batch of
  binder
• produced.
• Of these, some samples would be randomly
• selected and tested for compliance.
• Take additional samples if any changes or
  discrepancies are observed in any of the
  materials.

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AR BINDER PRODUCTION Continued
As long as interaction time and viscosity meet or
exceed minimum requirements, the AR binder may be
added to the aggregate, even if viscosity differs
from values shown in the design profile. The
design profile serves as a guide, not as a
specification. If viscosity during production
differs from design profile by 400 cPs or more
for corresponding interaction interval, obtain a
binder sample for compliance testing.

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AR BINDER PRODUCTION Continued
If viscosity falls below the minimum limit of
1500 cPs, the AR binder cannot be used for RAC.

To restore viscosity, the AR binder producer may
add up to 10 more CRM (using the design ratios
of scrap tire and high natural CRM) by total
binder mass.
1. The amount of CRM added shall be
documented 2. An additional 45 minute
interaction period is required after CRM
addition. 3. Viscosity of the adjusted AR
binder must comply with viscosity
specifications in order to proceed with
ARHM mix production
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ARHM MIX - Required Documentation
ARHM Mix Design including

• Individual and combined aggregate gradations
• Results of individual combined aggregate
  tests
• Aggregate source (s) and blend proportions
• Theoretical Maximum Specific Gravity/Density
• Design AR Binder content
• Design Air voids content
• Design VMA
• Hveem Stability

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Required Documentation Continued

ARHM Aggregate

• Individual and combined aggregate gradations
• Verify AC plant complies with CT 109
  requirements
• Check aggregate bins
• Sample aggregate cold feed
• Hot bins as appropriate and verify gradation
• Test Sand Equivalent as required

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Required Documentation Continued
ARHM Mix

• Verify ARHM mixing and discharge temperatures
• Visually inspect mix in haul truck before
  leaving plant

ARHM Mix Sample Tests

• Gradation
• AR Binder content
• Maximum Theoretical Specific Gravity
• Lab-compacted Air Voids
• Hveem Stability

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Required Documentation Continued

• Verify that haul trucks are tarped.
• Maintain inspector's log of pertinent information

1. List of samples obtained
2. Plant test results (aggregates mix)
3. Quantities of AR binder and ARHM mix
4. Binder production temps viscosity measurements
5. Other problems, items of note, events

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TEMPERATURE OF ARHM
SHOULD BE A MINIMUM OF 315 0F LEAVING PLANT
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SAMPLES
Paving Asphalt Asphalt Rubber Binder Crumb Rubber
Samples ARHM
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TESTING FOR BINDER CONTENT
IGNITION OVEN
INCOMPLETE IGNITION
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JOB SITE INSPECTION PRIOR TO PAVING
Pre-Construction Meeting

• Approved mix design
• Surface preparation
• Delivery method
• Rate of delivery
• Equipment in good working order
• Number and type of rollers (302-9.5)
• Other Issues (Refer to A-R Design Guide)
• Ambient and surface temperatures (gt50ºF)

Temperatures gt 60ºF are more effective in
achieving desirable compaction
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JOB SITE INSPECTION DURING PAVING

• RR distressed areas (dig-outs) complete?

• Cracks over ¼ -inch wide sealed?
• Caution Do not over-apply sealant to avoid
  creating
• fat spots in the new ARHM surface during
  compaction.

• Cold milling complete?

• Surface cleaned?

• Tack properly applied?
• Paving grade asphalt preferred

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a tack coatshall be uniformly applied upon the
existing pavement (302-5.4)
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JOB SITE INSPECTION DURING PAVING

• Paving machine moving at a uniform rate?

• Delivery rate of ARHM appropriate?
• If temperatures are marginally cold, do not
  windrow

• Automatic screed control working?

• Temperature of ARHM in trucks and hopper
• TEMPERATURE IS CRITICAL FOR ARHM

• Condition of the ARHM (Smoking, stiff, shiny,
• slumped, segregated)

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JOB SITE INSPECTION DURING PAVING
Rolling techniques

• Drive wheel forward
• Low side to high side
• Hot side to cold side
• Direction changes
• Sequence
• 1) Transverse joints
• 2) Longitudinal joints
• Breakdown passes (vibrator on)

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JOB SITE INSPECTION DURING PAVING

• Breakdown may require more than one coverage
• Need to get 95 of required compaction during
  breakdown to achieve target compaction
  requirements
• Temperature of mat at initiation of breakdown
  rolling (gt 290oF)
• Minimize handwork, raking and luting

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JOB SITE INSPECTION DURING PAVING
During ARHM placement

• Paving machine moving at a uniform rate?
• Collect load tickets and track tonnage placed
• Measure placement thickness and calculate yield
• Observe coordination between ARHM delivery and
  placement
• Record if trucks or paver are waiting
• Note any rejected loads of ARHM
• Observe delivery operations - are good practices
  being used?

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JOB SITE INSPECTION DURING PAVING

• Record if windrows are used.
• Monitor ARHM temperatures at spread (per
  Greenbook 290/300 to 330ºF) and during breakdown
  (290ºF) and intermediate compaction.
• Observe paver operations note discrepancies
  from good practice that might impact quality of
  joints or ride (smoothness).
• Joints at proper locations?
• Observe raking, luting, handwork. Broadcasting of
  excess mix or over-raking will damage the
  appearance of the finished pavement.

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JOB SITE INSPECTION DURING PAVING

• Observe compaction operations note
  discrepancies from good practice that might
  impact in-place density
• Breakdown roller(s) following immediately behind
  paver?
• Breakdown roller(s) using vibratory mode?
• Sufficient breakdown rollers operating to keep up
  with paver?
• Intermediate static roller(s) keeping up?
• Finish rollers effective?

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The asphalt concrete as delivered shall be
deposited directly into the hopper of the
spreading and finishing machine. (302-5.5)
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With the approval of the Engineer, the
Contractor may depositinto a uniformly sized
windrow, then pick up the material and convey it
with loading equipment provided. (302-5.5,
2006 Greenbook)
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Fully Automatic Screed Control Device
The machine shall be equipped with a suitable
full-width compacting screed (302-5.5)
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vibratory rollers using the vibratory mode
shall be used for initial break down rolling.
The initial coverageshall commence before
thetemperature falls below(280/2900F)
(302-9.5)
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Pnuematic rollers shall not be used.
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Casting from the side
At the option of the Engineer, when traffic
conditions warrant, a rock dust or sand blotter
may be required to avoid tracking. (302-9.6)
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Casting from the side
When thepavement has cooled to below(150o F),
the blotter may not be required. (302-9.6)
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JOB SITE INSPECTION AFTER PAVING

• Check the appearance of the finished surface for
  roller marks, scuffs, gouges, or other
  irregularities
• Check smoothness as required in project special
  provisions
• Visually evaluate quality of paving joints and
  identify any areas that may need to be sealed
• Identify core locations for compaction acceptance
  if applicable

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Lunch Time ARHM at rest
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TROUBLESHOOTING

• If any type of ARHM mix problem is suspected,
  obtain samples immediately and test for
  compliance with project special provisions
• Log full description of problem and related
  activities and report to the Engineer

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TROUBLESHOOTING
Possible Problems to Watch For

• Segregation Particle size segregation may be
  difficult to ID in coarse graded ARHM-GG
  mixtures. May appear segregated even if not,
• due to small percentage of fines included.
• When in doubt, sample
• ID affected truckloads and corresponding
  placement areas for info
• Size segregation is often accompanied by
  temperature segregation

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TROUBLESHOOTING
Smoke

• Blue smoke means that the mix is too hot and
  plant operating temperature needs to be adjusted
• White smoke is steam - too much moisture in the
  mix. May make mix tender and interfere with
  compaction. Aggregate needs to be dried longer
  before mixing with the AR binder

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TROUBLESHOOTING

• Stiff appearance Too cool or possibly somewhat
  low AR binder content. Check temperature and get
  a mix sample for further testing if needed.
• Dull, flat appearance Low AR binder content
  and/or excessive fines. Localized areas may
  indicate insufficient mixing or segregation. Get
  sample and test for gradation and AR binder
  content.

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TROUBLESHOOTING
Slumped and Shiny Appearance

• Typically indicates high AR binder content.
• Open-graded mixes may look this way and still
  meet specifications
• Old descriptive term is wormy mix seems to
  almost crawl while watched
• Some complying ARHM-GG mixes may also be wormy
• Visually check for binder drain down in the haul
  truck bed, sample and test for AR binder content
  and gradation

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SUMMARY

• Changes in the plant inspectors duties due to
  ARHM production are limited to
• Monitoring AR binder production and viscosity
  results
• Sampling AR binder and individual component
  materials for verification and acceptance
• Changes to field inspectors duties are very
  minor, primarily related to monitoring ARHM
  temperature and compaction operations

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TYPICAL ASPHALT PAVING FAILURES
Weathered Or Dry Surface

• Low binder content

• Overheated Mix

• Absorptive Aggregate

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TYPICAL ASPHALT PAVING FAILURES
Bleeding And Instability

• Too much binder

• Too much tack coat

• Too many aggregate fines

• Rounded aggregates

• Low air void contents

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TYPICAL ASPHALT PAVING FAILURES
Raveling

• Lean or overheated mix

• Low density/ under compaction

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TYPICAL ASPHALT PAVING FAILURES
Slipping

• Existing street not clean

• Improper tack coat

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QUALITY CONSTRUCTION THROUGH
QUALITY INSPECTION
YOU ARE THE KEY