Paver Operation 101 Paving for Uniform Texture and Smoothness RMACES February 2016
Paver Operation 101 Paving By The Numbers Paving for Uniform Texture Paving for Ride
Paving by the Numbers Step 1 Heat the Screed
Paving by the Numbers Step 2 Position Tow Arm Cylinders
Paving by the Numbers Step 3 Set Paving Width Based on the main screed width, set extender width per job specs Use scales on extenders Equal extender width on both sides whenever possible
Paving by the Numbers Step 4 Set Main Screed Crown per Job Specs
Paving by the Numbers Step 5 Set Extender Height (Angle of Attack)
Paving by the Numbers Step 6 Set Extender Slope per Job Specs
Paving by the Numbers Step 7 Prepare Screed Raise the end gates Select starting reference that is the proper thickness and length 0.9 1.2 m (3 4 ft) and position under extender pivot Support main screed and extender screed
Paving by the Numbers Step 7 Screed in Float
Paving by the Numbers Step 7 Lower the Screed Move the machine forward to remove the slack from the tow point
Paving by the Numbers Step 8 Null the Screed Null one side at a time Turn one depth control crank until no resistance is felt Repeat for the other depth control crank Check the first side again
Paving by the Numbers Step 8 Null the Screed Turn depth control crank in direction of increase until tension is felt Set other depth control crank the same way
Paving by the Numbers Step 9 2.5cm(1 ) Position End Gates Per Job Requirements Manual End Gates - lower to contact grade, apply 2.5 cm (1 inch) spring tension Hydraulic End Gates lower to grade
Paving by the Numbers Step 10 Set Auger Height Auger height affects mat texture Auger height of 5 cm (2 in) above the mat is right for most mixes Fine tune according to mix
Paving by the Numbers Step 11 Position Sonic Feeder Sensors Perpendicular to the live material flow. 46 cm (18 in) away from the material Target moving material
Paving by the Numbers Step 12 Set Feeder Controls
Paving by the Numbers Step 13 Manually Fill Auger Chamber Machine low idle Manually convey material out until material just touches auger shaft
Paving by the Numbers Step 13 Manually Fill Auger Chamber Machine low idle Manually auger material across screed face Auger material out to establish ½ level Do not overfill
Paving by the Numbers Step 13 No Fill Manually Fill Auger Chamber Using a shovel, hand fill area between last auger and end gate NOTE: Do not fill in area in front of screed extender on rear-mounted extender screeds
Paving by the Numbers Step 13 Feeder System All Auto
Paving by the Numbers Step 14 Set Accessory Functions Refer to O&MM for all accessory functions
Paving by the Numbers Step 14 Set Grade and Slope Controls Set grade controls to specifications Set slope control to specifications
Paving by the Numbers Step 15 5 3 2 6 4 1 7 Pull Off Starting Reference Pave mode (1), Screed in Float (2), throttle (3) Turn speed dial (4) to desired target speed (5) brake released (6) Move propel lever full forward (7)
Paving by the Numbers Step 15 Pull Off Starting Reference As paving begins Screed persons check material level at outboard end of augers Adjust mix height controls if needed to maintain material level at 1/2 auger
Paving by the Numbers Step 15 Pull Off Starting Reference As paving begins Operator checks center area of auger chamber. Adjust conveyor ratio controls if necessary to maintain material level at 1/2 auger
Paving by the Numbers Step 15 Pull Off Starting Reference As paving stabilizes Check auger speed Keep auger speed in 20 40 RPM range Avoid ON / OFF operation
Paving by the Numbers Step 15 No Separation Marks In Mat (Rear Mounted Extenders) Pull Off Starting Reference Screed personnel Check for transition marks Mat should be uniform
Paving by the Numbers Step 15 Extender Screeds Too Low (Rear Mounted Extenders) Pull Off Starting Reference Extender too low, mark in line with inner edge of extension Raise extender until line disappears
Paving by the Numbers Step 15 Extender Screeds Too High (Rear Mounted Extenders) Pull Off Starting Reference Extender too high, mark in line with outer edge of main screed Lower extender until transition line disappears
Paving by the Numbers Step 15 Keep speed constant Speed changes cause bumps or dips Adjust feeder system if speed must be changed
Mat Texture Basics Visual appearance of the surface Not the same as aggregate segregation Affected by many factors Goal is uniformity from edge to edge
Mat Texture Factors Texture affected by: - Angle of attack - Line of pull - Screed condition - Screed adjustments - Auger height - Type of mix - Temperature of mix - Paving Speed - Base condition
Mat Texture Angle of Attack 3mm (⅛ ) to 6mm (¼ ) Relationship between nose of screed and grade being paved 3mm to 6mm (1/8 to 1/4 ) Correct angle uses all of screed plate to create tight texture Angle of attack established at the start of each pull
Angle of Attack Correct angle of attack Flat angle of attack - adjustment needed Slough box - no adjustment possible
Angle of Attack Corrected Surface texture uniform after adjusting angle of attack Open texture behind strike-off unavoidable
Line of Pull Relationship between tow point height and screed pivot point height Same height above grade creates parallel line of pull Slightly upward line of pull acceptable Helps screed maintain stable floating condition
Screed Condition Condition of screed affects mat texture Texture striping indicates non-uniform pressure Check screed flatness
Centerline Stripe Centerline stripe can have several causes: - lack of lead crown - worn or missing reversing augers - reversing augers not installed correctly
Centerline Stripe Lead Crown 3mm (1/8 ) Place stringline on front and rear of main screed. Adjust main screed crown until 3mm (1/8 ) gap is present in center of main screed Helps large aggregate tuck under center of screed plate
Centerline Stripe Lead Crown Remove stringline across front of screed Keep stringline across trailing edge of main screed Place nuts under stringline on trailing edge at each end Turn center adjusters adjusters to flatten trailing edge Lead crown stays at leading edge of main screed
Centerline Stripe Temperature Variation Infrared image shows continuous cool centerline stripe Digital image does not show stripe Indicates dead area in center of auger chamber Inspect reversing or kicker paddles
Centerline Stripe Reversing Augers Reversing Auger Stagnant Mix Check condition of reversing augers Consider installing one pull-type reversing auger One auger segment pushing mix and one pulling mix will eliminate stagnant area
Centerline Stripe Reversing Augers Infrared image shows effect of installing push-pull auger segments Center of auger chamber now active Cold stripe eliminated Temperature within tolerance
Auger Shadows Texture stripes appear directly behind the augers Especially common when mix has large aggregates Raise augers until mat is tight and uniform
Strike-off Adjustment Strike-off setting affects angle of attack and mat texture Reference screed checks & adjustments manual for recommended settings Check height at beginning of each shift Adjust as required
Strike-off Too High Open Texture Large stone mixes create added lift Screed rides up Screed personnel decrease angle of attack Screed rides on its nose Open texture results
Strike-off Too Low Shiny Mat Sandy or fine grain mixes decrease lift Screed drops Screed personnel increase angle of attack Screed rides on trailing edge Shiny surface results Erratic screed control
High Spots & Spills Spills on grade Drag Marks Mix spilled on grade acts like high spot Screed drags cold mix Texture opens Smoothness & density suffer Clean all spills!
Preventing Defects Mat Texture Run slight nose-up angle of attack Adjust tow point height for parallel line of pull Check screed plate flatness Install lead crown (recommended to be the last option) Adjust strike-off height Position augers 5 7.5 cm (2-3 ) above mat surface Check mix temperature, especially when mix is stiff or sticky Set paving speed that does not tear mat Clean spills / remove high spots in the grade
Ride Quality Ride quality important on most projects May have pay factors tied to smoothness / roughness Ride quality influenced by many factors
Paving Speed Constant Speed Shear factor is constant Screed floats at same level assuming all other factors remain the same Fills in lows and scalps off highs Enhances smoothness Depth remains constant
Paving Speed Increased Increased Speed More energy to push material Shear factor decreases Depth decreases Automation will correct, or Correct manually Roughness introduced
Paving Speed Decreased Decreased Speed Less energy to push head of material Screed climbs Automation reacts to change in mat thickness
Constant Paving Speed Best ride quality with non-stop paving at one speed Only possible with material transfer device Expect 10% to 15% better ride quality through continuous paving
Settlement Marks 1-2 minute stops unavoidable during truck exchanges Mat will dent to some extent Normally shallow enough to roll out
Settlement Marks Observe settlement marks during breakdown compaction If marks disappear, no issue with ride quality due to normal paver stops
Low Head of Material Proper head of material covers one half the auger shaft Low level causes screed to drop Often happens during truck exchanges
Low Head of Material Screed drops Voids may appear Open texture and drag marks Lots of handwork to repair High roughness
High Head of Material Forces acting on screed increase Screed rises Often results from use of feeder system manual overrides Often due to poor set-up technique
Grade Sensor Reference Grade reference smooth and clean as possible Set up to track the same path on sloped surface Use accurate steering guide Sensor Path Steering Guide 2% Slope Mount sensor on tow arm not end gate when joint matching Helps eliminate unnecessary tow point movements
Grade Sensor Reference Keep sensor(s) away from spills Clean up all spills Choose new grade reference
Grade Sensor Position Single sensor just behind the tow point connection Sonic or mechanical, any brand Sensing string or surface Creates 1:1 tow point reaction Screed reacts over 5 tow arm lengths
Slope Control Slope negatively affects ride quality Slope only base or binder Auto slope control drives large tow point movements Screed reacts quickly
Preventing Defects Ride Quality Continuous paving (MTVs) Calculated, consistent paving speed Short stops between trucks Screed assist for tender mixes Consistent head of material Proper set-up for wide width paving Proper grade reference Sensor position Using slope correctly Averaging ski selection