Extending Performance with Proper Asphalt Compaction

Ken WalschlagerMilestone Contractors

Compaction is 90% rolling – the other half is preparation…

Compaction is the process of reducing the volume of a mass of material – making it more dense. Design Proper production Sub-base/drainage Good paving practices Lift thickness

Compaction is key…

Better Compaction results in… Extended pavement’s life of service Greater strength to support heavier

loads Increased resistance to rutting Reduced permeability of water and air Overall durability

Proper HMA Design

Different designs for different applicationsSpecial mix designs OG Porous SMA 4.75 Thin Lift What about Warm Mix?

Proper Depth

Nominal Mix Design 9.5mm 12.5mm 19mm 25mm 4.75mmMax Partical Size 12.5mm 19mm 25mm 37.5mm 9.5/12.5mmMinimum Depth 1" 1.5" 2" 3" .55"Maximum Depth 2" 3" 4" 6" 1 1/8"Recommended Depth 1.5" 2" 3" 4.5" 1"Wedge/Level Max 3" 4.5" 6" 9" ????

Back to design…

Proper Production

Stockpiles built correctly and tested?Loader using correct methods?Plant calibrated?Right blend entered?Proper loading of haul trucks?Trucks equipped with tarps?

Proper Laydown

Surface properly prepared/tacked?Mix dumped properly into buggy/paver?Hopper not run empty?Flow gates/auger speed set correctly?Proper head of material?Auger height correct/constant motion?Paver operated at constant speed?Depth as uniform as possible?

Proper Depth – it’s important

Deep enough for aggregate structure

Nominal Mix Design 9.5mm 12.5mm 19mm 25mm 4.75mmMax Partical Size 12.5mm 19mm 25mm 37.5mm 9.5/12.5mmMinimum Depth 1" 1.5" 2" 3" .55"Maximum Depth 2" 3" 4" 6" 1 1/8"Recommended Depth 1.5" 2" 3" 4.5" 1"Wedge/Level Max 3" 4.5" 6" 9" ????

Before rolling operations begin

Proper maintenance – read operators manualOperator Safety – get familiar with rollerCheck water system Release agent?Confirm frequencies

Rollers

Static Double drum 3 Wheeled Pneumatic Tire

VibratoryOscillatoryCombination Rollers

Static Rollers

Variables Weight, speed, rolling pattern When? OG, Porous, SMA, 4.75mm*

Vibratory Rollers

Variables Amplitude Frequency Speed (impact spacing)

Amplitude

Lower Amplitude Variable Higher Amplitude

Thinner <2" Lift Thickness Thicker >2"

Lower Grade PG Grade/Viscosity Higher Grade

Rounded/Gravel Aggragates Angular/Crushed

More open Gradation Dense

High Ambient/Mix Temp Low

Frequency

Impact Spacing Check owners manual.

Impacts per foot

Frequency (VPM) Feet/min mph Feet/min mph Feet/min mph2600 325 3.7 260 3.0 217 2.52800 350 4.0 280 3.2 233 2.73000 375 4.3 300 3.4 250 2.83200 400 4.5 320 3.6 267 3.03400 425 4.8 340 3.9 283 3.23600 450 5.1 360 4.1 300 3.43800 475 5.4 380 4.3 317 3.64000 500 5.7 400 4.5 333 3.8

1800 225 2.6 180 2.0 150 1.7

feet / min=VPM VPM impacts/ft

8 10 12

Frequency

Correct impact spacing

Roller Speed

Paver = Plant = Trucking # of Passes of breakdown roller Frequency setting Tender Zone? Roller width/paving width

Paver/Roller Speed

Do not out run your rollers. 3.5 mph roller300ft/min – 3 wide to cover X 4 passes

300/12=25ft/min 85% rolling = 21 ft/min paver speed(140tph)

300ft/min – 2 wide to cover X 4 passes300/8=37.585% rolling = 32 ft/min paver speed(211tph)

Rolling

Turn towards the shoulder(away from traffic) stopping at an angle. Make sure vibration is turned off before stopping.Be sure not to turn wheel while stopped.Break down when asphalt is at its hottest.Cover entire mat with one pass before starting 2nd.

Rolling cont.

Take previous stop marks out with next pass.As paver moved forward, roll up to paver with each pass to seal in heat. Roll handwork as soon as possible.Proper longitudinal joint construction. Stay on hot mat Know when to “pinch the joint”

Cross-roll transverse joints.

Porous/OG

Static onlyStrength through design with aggregate structure and modified ACVibration can cause over compaction

Stone Matrix Asphalt

Static roll onlyRoll as hot as possibleTypically no tender zoneRoll until cool – little concern of over-rolling

Warm Mix

Easier to compactHigher densities reportedOpen to traffic soonerUse same good rolling procedures as HMA

Summary

Good designProper productionProper paving practicesGood rolling techniquesStay watchful – things change…

Thanks

Questions?