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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)