Principles of paving
Sponsored Links
This presentation is the property of its rightful owner.
1 / 44

Principles of Paving PowerPoint PPT Presentation


  • 400 Views
  • Uploaded on
  • Presentation posted in: General

Principles of Paving. Paver System Five. Grade Control Systems Tremendous benefits to the paving contractor: Increase efficiency and productivity Control Material Quantities Improve smoothness and rideability Increase jobsite safety. Control Sensors. Slope Control. Laser Control.

Download Presentation

Principles of Paving

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Principles of Paving


Paver System Five

  • Grade Control Systems

  • Tremendous benefits to the paving contractor:

  • Increase efficiency and productivity

  • Control Material Quantities

  • Improve smoothness and rideability

  • Increase jobsite safety

Control Sensors

Slope Control

Laser Control

= Theanswer for perfect, smooth paving?

Sonic Control

Smoothtrac

Sonic Averaging System


Paver System Five

Good Paving Practice

Grade Control

Decent paving

Control Sensors

Control Sensors

Control Sensors

=

+

Fair paving

=

+

Great paving!

=

+


Principles of Paving

  • Good principles of paving must come BEFORE Grade Control

  • Paving is a TEAM project

  • Grade control is a great tool to help the paving team:

    • be more efficient

    • control material quantities

    • provide a smoother surface

Train the entire TEAM!


Paver Components

  • Asphalt Paver

  • The paver has two primary components:

  • Tractor

  • Screed


Paver Tractor

  • Tractor has two primary functions

  • Material Handling

  • Forward Movement


Paver Tractor

  • Asphalt distribution

  • The paver typically receives the asphalt:

  • directly from a truck

  • by a pickup machine (windrow elevator)


Paver Tractor

  • Asphalt distribution

  • The asphalt is received into the paver’s hopper

  • Hopper is a holding station for the asphalt

  • The operator tilts the hopper to deliver material into the feeder conveyor


Paver Tractor

  • Asphalt distribution

  • Feeder conveyors distribute the asphalt to the augers

  • The augers spread the asphalt in front of the screed

  • End gates contain the material at the outer edge of the screed


Screed Components

  • Paver Screed

  • Function of the screed is mat laydown

  • Screed has several components


Screed concept

  • The screed floats on the asphalt as it passes under the screed plate

  • The screed will “self-level” and maintain a thickness based on the forces acting on the screed.

Floating, Self-Leveling Screed


Screed Concept

  • The desired thickness is controlled by the screed angle of attack

  • As the angle of attack is increased or decreased, the screed will float up or down changing the thickness

Screed angle of attack…

…controls mat thickness


Changing Angle of Attack

  • The angle of attack can be changed by:

  • The manual crank

  • The hydraulic cylinder at the tow point


Screed Concept

If the angle of attack is…

increased,

decreased,

Mat thickness decreases

Mat thickness increases


Floating, Self-Leveling Screed

  • The paver tractor, and therefore the screed tow point, travel over the existing “rough” surface

  • The floating screed doesn’t react immediately to the variations in the tow point path

  • The floating screed seeks it’s own level, smoothing out small humps and bumps.


Floating, self-leveling screed

  • The floating screed naturally cuts off high spots and fill in low spots.

Cuts off high spots

Fills in low spots


Screed Reaction

  • Tow point “step disturbance” and screed reaction

  • Two point is changed by a unit of one (1)

  • Net effect = the angle of attack has been changed


Screed Reaction

  • Example of tow point “step disturbance” and screed reaction

  • Two point is changed by a unit of one (1)


Screed Reaction

Example of change in angle of attach by turning manual crank and screed reaction.


Checking Mat Depth

  • Goal is to “average” a particular paving thickness

  • Always check several places, horizontally and laterally


Adjusting Mat Depth

  • Once an adjustment is made – GIVE THE SCREED TIME TO REACT!


Adjusting Mat Depth

Goal – Provide smoothness and compaction, while hitting target tonnage for entire project!

  • Determine average depth by measuring tons/mile

  • Make small adjustments based on calculation


Floating, Self-Leveling Screed

Left alone, the screed will self-level and assume a thickness based on forces that are acting on the screed.

  • What are these forces?


Forces Acting on the Screed

There are four major forces acting on the screed


Forces Acting on the Screed

  • If any one of these forces change, the mat thickness will change.

  • But in “real life” job applications, these forces cannot always remain constant.


Tow Point Force

If the forward speed…

increases;

mat thickness will decrease

decreases;

mat thickness will increase

Goal - Non-stop, continuous paving!


Tow Point Force

Goal - Non-stop, continuous paving!

  • Determine paving speed based on plant supply in tons/hour

  • Regulate trucks to the paving supply and operation, not the paving operation to the trucks

Plant supply = 210 tons/hour

Paving speed = 25’/minute


Tow Point Force

Maintain smooth truck exchange!

Bump in matat every truck exchange

(probably “caused by faulty grade control!”)


In Motion Switches

  • While stopped waiting for trucks, the screed will settle slightly

  • Screed goes down, the tracker will also go down slightly


In Motion Switches

  • Grade control would want to drive the tow cylinder up to compensate

  • The paver’s In-Motion switch stops the valve electrical signal

  • A timer initiates the electrical signal after the paver is in-motion

X


Head of Material Force

Maintain a CONSISTANT head of material


Head of Material Force

Maintain a CONSISTANT head of material


Head of Material Force

Maintain a CONSISTANT head of material


Reaction of Material Force

  • Mix Characteristics

  • Gradation

  • Segregation

  • Mix Temperature


Weight of the Screed Force

Compaction Force = Pounds per square inch


Weight of the Screed Force

  • Compaction Force = Pounds per square inch

  • How can the weight force change? (lbs per square inch)

  • People climbing on and off the screed can have a small effect on overall screed weight


Weight of the Screed Force

  • Screed extension

  • Changing screed width changes the compaction force - Lbs per square inch


Roller Compaction

  • Good rolling practice is critical to the quality of the mat


Roller Compaction

  • A freshly laid, smooth mat will reflect some of the original surface after rolling

  • Quality of the base being paved affects smoothness

  • Multiple lifts help to minimize these effects


Mechanical condition of the Paver

  • The paving machine itself needs to be in good shape and adjusted correctly

  • Feeder system

    • Hopper, flight chain operation and adjustment, augers, etc.

    • Operation and adjustment of feeder controls

  • No excessive wear on screed components

    • Screed plates

    • Thickness control screws, bearings, and bushings

    • Screed pivot point bushings

  • Screed adjustment

    • Strike off plates

    • Screed flatness

    • Screed extensions adjusted properly, elevation and slope


Paver System Five

Good Paving Practice

Grade Control

Decent paving

Control Sensors

Control Sensors

Control Sensors

=

+

Fair paving

=

+

Great paving!

=

+


Paver System Five

  • Tow point is smoothly controlled to a desired path:

  • Curb

  • Stringline

  • SAS smoothing out existing surface

Then let the floating, self-leveling screed do it’s job!


Best Paving Practices

  • Good mechanical condition of the paver

  • Minimize changes in the natural forces on the screed

  • Non-stop, continuous paving

  • Good, smooth truck exchange

  • Constant paving speed

  • Constant head of material

  • Consistent mix characteristics

  • Good rolling techniques

  • Good quality of sub-base

  • Understand proper setup and operation of Grade Control


Principles of Paving


  • Login