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Administration of Asphalt Specifications

Placement

Placing of Asphalt Clause 8

Aim to produce §  Homogeneous product §  Tightly bound surface §  Uniform bond with substrate §  Specified surface properties

Placing asphalt to Specification

§  This module will focus on : ›  Pavement preparation (Clause 8.2) ›  Method of placement (Clause 8.3) ›  Protection of Work (Clause 8.4) ›  Course & layer thickness (Clause 8.6) ›  Pavement temperature & weather (Clause 8.7) ›  Paving & Compactions (Clause 8.8) ›  Tack coat (Clause 8.9) ›  Joints (Clause 8.10) ›  Placement Trial (Clause 8.11) ›  Temporary ramps (Clause 8.12)

Pavement Preparation (Clause 8.2.2)

  Cleaning –  Dry –  Swept

  To help create an effective

intra-layer bond

Vacuum Broom Rotary broom on skidsteer

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Hand broom Water flushing

Bond failure due to surface contamination

Existing pavement markers must be removed prior to paving

Pavement Preparation (Clause 8.2)

Pavement repairs

Crack Sealing (Clause 8.2.3)

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Crack Sealing- Excess joint filler Strain Alleviating Fabric Strips (Clause 8.2.4)

Preparation of pavement

Pavement repairs §  Cleaning §  Cold milling

Cold milling operation

Cold milling operation

Large milling drum and cutting teeth

Fine milling drum

Cold milling operation Milled asphalt surface Tooth spacing governs groove depth

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Result of poorly maintained milling drum Water infiltration between layers

Placing Asphalt

§  Pavement preparation (Clause 8.2) §  Method of placement (Clause 8.3)

Placing asphalt

›  Pavement preparation (Clause 9.2) ›  Paving equipment (Clause 9.3)

Asphalt to be placed by: - self-propelled paving machine - with automatic level control

Paver Components

Screed

Leveling arm

Dashboard

Tow point Steering wheels

Hopper Engine hood

Push roller

Slat Conveyor Screed operator position

Asphalt Feed Control System

Conveyor

Hopper

Augers

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Free Floating Screed

Angle of attack Head of material

Paving speed

The screed rises if:

  the head of material increases

  the speed of the tractor decreases

  the material temperature drops

  the asphalt mix becomes coarser

The screed settles if:

  the head of the material decreases

  the speed of the tractor unit increases

  the material temperature increases

 

Material bulk in front of screed to high.

Material bulk in front of screed to low.

Factors affecting the screed

The height of the screed remains constant only if all forces acting on the screed are in equilibrium.

Auger correct adjusted and material bulk in front of screed optimal.

Factors affecting the screed

Extendable Screed Poor auger configuration

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Proper Paver configuration Paver and auger setup

Segregation caused by auger speed and setup

Horizontal Location Level control

Marking of required placement depth is essential to effective process control

Chasing levels by hand requires skill and knowledge of plant reaction time.

Automated level control

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Sonic averaging beam

Automated level control

Sonic sensor

Automated Level Control

E x is tin g le ve l

  Thickness table from design is entered into the screed controller   Thickness is adjusted to account for compaction

Rolling survey control Method of Placement (Clause 8.3)

§  Asphalt to be placed by machine §  Hand placement only for:

§  minor correction of existing surface §  where use of paver is impracticable §  Broadcasting or overworking asphalt leads to segregation

Method of Placment (Clause 8.3)

Asphalt to be placed by machine Hand placement Echelon paving: If specified, in Annexure PSTS31.1

Echelon paving (Clause 8.3) §  Large scale projects §  Free from public traffic §  Does not have constrained site

conditions

Two pavers in echelon Three pavers in echelon

§  Full width paving is possible §  High production rates

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Feasibility and success depends on

§  Constant supply rate §  Provision for traffic §  Efficient truck marshalling §  Dedicated truck controller §  A good paving line and overlap §  Well drilled compaction effort §  Temperature monitoring

Method of Placement (Clause 8.3)

§  Asphalt to be placed by machine §  Hand placement §  Echelon paving §  Material Transfer Vehicle (MTV)

Material Transfer Vehicle

§  Benefits §  Buffer between trucks and paver §  Acts as surge bin §  Remixing ability

§  Limitations §  May exceed weight restrictions on

structures when loaded §  Maneuverability – avoid confined

areas e.g. tapers, turning lanes, roundabouts < 50m radius

Material Transfer Vehicle

  Avoid  emptying  hopper  and  MTV    Keep  hopper  2/3  full    Less  drop  height  minimises  segrega�on    Avoid  paving  out  mix  in  the  hopper  

Remixing effect of MTV

186.6 164.2 145.0

141.9

107.2 128.3

111.5

127.1

102.1

137.9

*>160.0°C

*<50.0°C

60.0

80.0

100.0

120.0

140.0

160.0

139.5138.0139.5134.5

136.6132.3 134.5

137.5

*>160.0°C

*<50.0°C

60.0

80.0

100.0

120.0

140.0

160.0

Without With

Placing Asphalt

§  Pavement preparation (Clause 8.2) §  Method of placement (Clause 8.3) §  Protection of work (Clause 8.4)

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Protection of Works (Clause 8.4)

It is the Contractor’s responsibility to ensure the asphalt has cooled sufficiently prior trafficking to minimise deformation of the asphalt. …

Clause 8.1 §  The application of water to induce rapid cooling in the asphalt shall not

be used at any stage in the process, including preparation for trafficking, unless approved by the Administrator.

Placing Asphalt

§  Pavement preparation (Clause 8.2) §  Method of placement (Clause 8.3) §  Protection of work (Clause 8.4) §  Protection of services and road fixtures (Clause 8.5)

Protection of services and road fixtures (Clause 8.5)

Quality plan Handwork around pits and bridge joints

Placing Asphalt

§  Pavement preparation (Clause 8.2) §  Method of placement (Clause 8.3) §  Protection of work (Clause 8.4) §  Protection of services and road fixtures (Clause 8.5) §  Course & layer thickness (Clause 8.6)

Course and layer thickness (Clause 8.6)

What is a course?

§  Specified thickness of one type of mix

§  Can be made up multiple layers

What is a layer? §  Asphalt laid in a single

pass of the paver

AC10  -­‐  Layer2  

AC10  -­‐  Layer  1  

Cou

rse

AC10  Course  

Course and layer thickness requirements

What is Specified or Nominated What is placed

Clause 8.6.1 – Nominated Layer Thickness   Course depth will be specified in drawings   Layer thickness may be specified otherwise

nominated by contractor   Thickness limits (Table 8.6.1), range asphalt

which may be effectively laid & compacted   Approximately 3.0-5.0 times the nominal

Mix Size

Clause 9.3 – Tolerance on average and individual layer thickness as laid.   Affect pavement life   Drainage   Influence adjoining structures

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Corrective courses and tie-ins

§  May need to lay outside thickness limits §  Reduce risk of differential compaction §  Match into existing levels

§  Contractor will submit work method to achieve dense and homogenous layer

Surveillance checklist - Placement

§  Are Contractor Asphalt Works Checklists and ITPs available and being used?

§  Staffing levels as per Contractor’s Project Quality Plan §  Suitable action to protect and maintain fixtures and Services

within work area. (cover grates, hydrants etc)

§  Pavement temperature is suitable to proceed with works §  Asphalt is placed and compacted within temp. range

according to binder manufacturers recommendations. §  Thickness correct (allow for compaction)

Surveillance checklist - Placement

§  Driving line §  Constant forward speed §  Flatness of mat §  Homogeneity §  Use of auger extensions §  Constant auger speed §  Smooth truck engagement §  Clearing spillages in front of hopper §  Delivery Dockets §  Measuring temperatures

Asphalt Surveillance - Mix Code

Check that mix code represents the accepted nominated mix Replace with Qld examples.

Placing Asphalt

§  Pavement preparation (Clause 8.2) §  Method of placement (Clause 8.3) §  Protection of work (Clause 8.4) §  Course & layer thickness (Clause 8.6) §  Pavement temperature and weather conditions (Clause 8.7) §  Paving and compaction temperatures (Clause 8.8)

Pavement Temperature and Weather

Pavement Temperature and Weather Conditions Clause 8.7 §  Pavement must not be wet. §  Rain must not appear imminent. §  Measure pavement temperature every 2 hours

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Pavement Temperature (Clause 8.7)

§  Affects cooling rates

§  Affects compaction time

§  Affects plant requirements

§  Minimum temperatures in Table 8.7

Paving and Compaction Temperature (Clause 8.8)

Quality plan must include:   Minimum temperature asphalt is paved at   Minimum temperature of mat when initial compaction will commence   How this will be measured

Typical asphalt compaction temperatures Temperature Measurement

Surveillance of mix temperature and traceability records

Other examples of temperature monitoring

Temperature Measurement Infrared Thermometers

§  Must be accurate to ± 2°C §  Verification of accuracy daily ?

§  Compare against reference device e.g. calibrated infrared thermometer with NATA certificate

§  Range of temperatures e.g. one pavement and one mix temperature reading

§  Use difference as temperature offset Product specifications

Infrared temperaturerange

566: -40 °C to 650 °C (-40 °F to 1202 °F)568: -40 °C to 800 °C (-40 °F to 1472 °F)

Infrared accuracy < 0 °C (32 °F): ± (1.0 °C (± 2.0 °F) + 0.1°/1 °C or °F);> 0 °C (32 °F): ± 1 % or ± 1.0 °C (± 2.0 °F), whichever is greater

Display resolution 0.1 °C / 0.1 °F

Infrared spectral response 8 µm to 14 µm

Infrared response time < 500 msec

Thermocouple Type-Kinput temperature range

-270 °C to 1372 °C (-454 °F to 2501 °F)

Thermometers: Fluke 568and 566

Overview Features Specifications Models and Accessories More Info

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Uniform temperature is vital for uniform density

What is an acceptable level of temperature variation?

Compaction

Method of achieving compaction §  Roller type §  Number of passes §  Rolling pattern

May need to vary for §  Temperature §  Layer thickness §  Paving speed

Example number of roller passes

Min.  4  passes  of  vibra�ng  steel  roller    

Min.  10  passes  of  mul�-­‐tyred  roller    

Min.  2  passes  of  steel  roller,  sta�c  mod  

Usually  vibra�ng  but  may  have  a  sta�c  pass  on  difficult  mix  

Consistent compaction effort over whole of mat

Typical Rolling Pattern Temperature Zones

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Steel Drum Rollers

  Smooth drum surface   Water spray operational   Scraper in good order   Frequency matches roller speed

Amplitude

§  Compaction amplitude is half

the total downward movement

§  Compaction occurs from both ground vibration & drum impact

Amplitude

Frequency & Impact Spacing Multi tyred Rollers

  Tyres and mats in good condition   Water spray operational   Tyres correctly inflated to manufacturers

recommendations   Warm tyres before rolling

Surveillance checklist

§  Paving and rolling process produces an homogeneous finish with tightly bound surface.

§  Rolling pattern matches paver output, as specified in the Quality Plan and consistent throughout placement.

§  Number of rollers keeping up with paver and plant output

Typical surveillance checks - Compaction

§  Temperatures §  Cleanliness §  Warm up §  No oil leakage §  Water spray working and effective §  Operator safety §  Even rolling patterns §  Smooth speed and direction change §  Bow wave bumps §  Edge treatment

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Placing Asphalt

§  Pavement preparation (Clause 8.2) §  Method of placement (Clause 8.3) §  Protection of work (Clause 8.4 §  Course & layer thickness (Clause 8.6) §  Pavement temperature and weather conditions (Clause 8.7) §  Paving and compaction temperatures (Clause 8.8) §  Tack coat (Clause 8.9)

Is this tack coating acceptable ?

Tack Coat Application rate

  0.1 to 0.2 l/m2 of residual bitumen (Not emulsion)   Even application with mechanical applicator

Tack Coat Application rate

  Approximately double application rate for joints, kerb faces, etc.   Hand work where mechanical applicator impractical

Tack coat

§  Endorsed daily record ? §  Certified by supervisor §  Binder content – amount of bitumen as a %

Lot  No.   Volume  (L)  

Binder  Content  (%)  

Area  (m2)  

Applica�on  Rate  (L/m2)  

1   720   30   1200   0.18  

2   360   60   1200   0.18  

(720 x 0.3 ) ÷ ( 1200 ) = 0.18 L/m2

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Tack coat must:   be intact at the commencement

of paving   effectively bond between

layers.

Condition of tack coating

Placing Asphalt

§  Pavement preparation (Clause 8.2) §  Method of placement (Clause 8.3) §  Protection of work (Clause 8.4 §  Course & layer thickness (Clause 8.6) §  Pavement temperature and weather conditions (Clause 8.7) §  Paving and compaction temperatures (Clause 8.8) §  Tack coat (Clause 8.9) §  Joints (Clause 8.10)

Joints (Clause 8.10) §  Implement procedures to maximise joint density §  Mechanised edge compaction or trimming §  Loose or cracked material removed before placing adjacent run

Edge pressing tools Edge trimming tools

Edge Cutter

Saw cutting

Profiler

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Minimise density differential at mat edge

Minimise density differential at mat edge

In-situ Air Voids (Nuclear Gauge @ 200mm intervals transverse)

Joints (Clause 8.10)

Finish surface smooth, planar and coinciding with the surface of the rest of the mat

Longitudinal Joints (Clause 8.10)

§  Coincident with final traffic markings in surface layers §  150mm from the line of change of cross fall §  Offset by 150mm from joints in underlying layers

Where's the joint? Straight drivelines are critical to joint density

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Handwork on joints

§  Overlap previous run

§  Push overlapping asphalt to form ridge on joint

§  Remove segregated material

§  Do not spread across mat

Dense graded asphalt

Aim for no more than 150mm

Remove excess and segregated material

Transverse Joints (Clause 8.10)

§  Where §  Minimum 25m apart §  Offset 1m from joint in underlying layer §  Consider if practical for road location and geometry

§  When §  Commencement of each paving run §  When mix has cooled below initial compaction temperatures

Transverse joints

Definition of hot joints

§  Temperature of first mat not less than minimum recommended for effective compaction.

§  Edges of adjoining mats compacted in same process.

§  Effectively limited to echelon paving

Definitions of warm and cold joints

Warm Joints §  Temperature of first mat must not be less than minimum

recommended for final rolling §  Generally only 1% to 2% lower density

Cold Joints

§  Everything else

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Joint construction in Quality Plan

§  Procedure to achieve joint quality, density and location §  May include:

§  First placed mat must be planar (edges not rolled over). §  Edges must be in a straight line or uniform curve §  Mechanical edge compactor or trimmer §  Remove cracked or boney edges. §  Pave second mat with appropriate compaction allowance and

overlap. §  Push back overlap without broadcasting. §  Compact joint progressively. §  Manage temperature/density throughout process

Placing Asphalt

§  Pavement preparation (Clause 8.2) §  Method of placement (Clause 8.3) §  Protection of work (Clause 8.4 §  Course & layer thickness (Clause 8.6) §  Pavement temperature and weather conditions (Clause 8.7) §  Paving and compaction temperatures (Clause 8.8) §  Tack coat (Clause 8.9) §  Joints (Clause 8.10) §  Placement Trial (Clause 8.11)

Placement Trial (Clause 8.11)

Where to use it §  Major projects §  High production volumes §  Untried mixes §  Crew inexperienced with mixes/plant

Where not to use it §  Minor works §  Maintenance activities §  Proven mixes §  Experienced crew

What is being trialed §  Nominated mix §  Plant capability §  Crew competency

Placing Asphalt

§  Pavement preparation (Clause 8.2) §  Method of placement (Clause 8.3) §  Protection of work (Clause 8.4) §  Course & layer thickness (Clause 8.6) §  Pavement temperature and weather conditions (Clause 8.7) §  Paving and compaction temperatures (Clause 8.8) §  Tack coat (Clause 8.9) §  Joints (Clause 8.10) §  Placement Trial (Clause 8.11) §  Temporary Ramps (Clause 8.12)

Temporary Ramps and Tie-ins (Clause 8.12)

Transverse joints

Temporary Ramps and Tie-ins (Clause 8.12) Transverse joints - ramp length for every 50mm of height

50mm

50mm

2.5m

1.5m

≤

≥

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Temporary Ramps and Tie-ins (Clause 8.12) Longitudinal joints - 1.0m ramp length for every 50mm of height §  Will ramp will fall within wheel path ? §  Assess if delineation to prevent travel over joint and omission of ramp is safer.

50mm

1.0m

Surveillance checklist

§  Transverse and longitudinal edges are ramped correctly when they are to be opened to traffic.

§  Ramps are suitable formed around manholes, grates and covers etc when they are to be opened to traffic.

§  Clean up of milled area suitable for next construction process. (Tackcoat/Sprayed seal/asphalt etc)