March 22-24, 2016 | Nashville, TN | www.worldofasphalt.com

Pave IR & Rolling for Density

PRESENTED BY:

MARK BURROW – LONGVIEW ASPHALT, INC.

This is how we get paid…DENSITY

Pave IR is a Tool in our Box

• TxDot has created TX 244-F as a compliance specification utilizing the Pave IR System

• TX 244-F test procedure is looking for both Thermal and Material Segregation

• Pave IR scans the mat every 6 inches for the full length of the paving day

• The Paving crew has on NO CLOTHES

Asphalt Mix Design• Design a stable mix with enough AC • Dry mixes cause Thermal and Material

Segregation and low Density• The higher the PG asphalt grade the stiffer the

mix• RAP or RAS also stiffen the mix usually causing

the mix to allow for one PG grade bump down• HMA or WMA: Is the mix foamed?

o Astec Green foam or Chemical (Evotherm)

Hot Mix Plants

• Plants operated correctly, do not cause Thermal or Material Segregation provided they are maintained to the Manufactures specification

• The plant must produce the mix at a UNIFORMED TEMPERATURE

• Once the mix exits the drum, you can never add any more heat

Make the Mix Hot

• Heat (BTUs) turns AC into a liquid which acts likes a grease in the mix

• Hot Liquid AC is a Compaction AID• Tender Zone 220F – 170F is the AC’s

phase change from a grease to a glue• Temperatures < 169F the Liquid AC is

becoming a glue to bind the mix matrix together

Trucking

• Best practice for loading trucks is the 3 drop method (front, middle & rear drops)

• Conservation of Heat (BTUs) o Use fully sealing vinyl tarps on the truckso Insulated truck beds are great

• Thermal and Material Segregation will always be found in the front of a truck bed

The Worst Pave-IR ResultsDirect End Dump to Paver

This truck is equipped with a roll back tarp but we regularly see 50F lower temperature in the front of the truck bed

TARP <50F

Direct Dump Thermal and Material segregation flow directly in and out of the paver and shows up as truck ends

Remixing with MTV• The MTV provides two vital functions

o Re-blending of the mix to eliminate Thermal Segregation

• We regularly see 50F lower mix temperatures in the front of truck bedso Remixing will re-blend the Thermal

segregation to < 25F segregation o Re-blending of the mix eliminates Material

Segregation

MTV Solves Thermal & Material Segregation in the C-2 Hopper

1/3 Course Rocky Mix

1/3 Well Blended Mix

1/3 Finely Blended Mix

Material Segregation Thermal

Segregation

1/3 Hot

1/3 ModeratelyHot

1/3 Cool Mix

BTU Venting to Atmosphere

Once the dumping process starts, BTUs are venting to the atmosphere. The Paving Crew can only work with mix (BTUs) delivered.

BTUs Venting to Atmosphere

Keep your C-3 boom as low as possible. This is fluffing your mix with cold air.

Poor hopper loading will CAUSE MATERIAL SEGREGATION

Computer ScreenPave IR Bar with 13 infra-red

Temperature probes.

PAVE-IR

Pave-IR Scanning Head is Replacing the IR Bar

Pave-IR Benefits

Paving Crew can Self Monitor & Self Adjust

• Continuous paving speed monitored• Continuous thermal temperature displayed• Continuous paver stop duration readings

in minutes• Paving crew can instantly tell if the plant

production temperatures are varying

Pave-IR

Mounts on paver

13 Infra-red temperature sensors

Non-destructive & 100% coverage

Is a real time continuously temperature display of the mat as it is placed

Green is good > 75% of paving. 0 F – 25 F Heat Loss

Moderate can = 20% Yellow = 25 F - 50 F Heat Loss.Server can = 5 % Red = + 50 F Heat Loss. Borderline on not getting density.

8 Foot Paver stops. The program allows this without any penalty

Complete Moba Pave- IR Package

• Scanner Head

• GPS Antenna

• Computer

Moba Pave- IR Computer

• Time & Date

• GPS Coordinates

• Real Time Mat Temperature Recorded and Displayed

• Real Time Paving in FPM

Graphically Displayed Paver Speed in Ft/Min

The RED VERTICALLINES are paver stops

Graphically Displayed Paver Stop in Minutes

The Thermodynamic heating of the existing pavement by the new mix and the cooling of the newly laid pavement, should determined the duration of allowable paver stopping time in minutes

Graphically Displayed Thermal Profile Station 284+00-321+00

Best (#1) Pave-IR Results End Dump Truck to MTV

Best (#1) Pave-IR ResultsEnd Dump truck to MTV

There are a wide array of purported remixing devices on the market, but only devices equipped with triple pitch auger are true remixers

Experience has shown that the hot mix will loose 20 degrees F to the atmosphere as it is dumped from an end dump truck, conveyed through the MTV, and laid by the Paver

It is all about UNIFORMITY of Thermal and Material Segregation

2nd Best Pave-IR Belly Dump Windrow to MTV

2nd Best Pave-IR ResultsBelly Dump Windrow to MTV

• 95% of the mix is picked up and re-blended for both Thermal and Material Segregation

• Best dumping practice is to have no more than 2 loads spread on the roadway at a time

• Over lap end of loads 30-50 feet• Insulated the belly dump gates

2nd Best Pave-IR, Windrow - MTVThermally Segregated end of the load is overlapped with the nexthot load

313 – 214 degrees.

MTV will remix the Thermally Segregated mix

3rd Least Favorable Pave-IR ResultsDirect Belly Dump to Windrow Elevator

• Mix dumping and truck load overlap is critical (30 to 50 Foot overlap)

• Least repeatable result for Thermal and Material segregation

• 95% of the mix picked up and placed in the paver insert hopper

• Should equip the paver insert hopper with a re-blending apparatus

3rd Least Pave-IR Results

3rd Pave-IR, Windrow - PaverServer Thermal Segregation >50FPaving on the borderline all the time!!!

The Science of Rolling• Paver Speed < 41 FPM this is possible

because of MTV 25 ton surge capacity • Total dump, pave, roller elapse time = 10

minutes• We MUST be finished with the break down

rolling pattern before the mix drops below 220 F

• WMA temperature range is 285 F – 220 F• Ladies & Gentlemen, we are laying HOT

Mix but we are rolling Warm Mix everyday

Beware of Temp < 220 F

The Break Down Rolling is completed prior to Temp Limit of < 220 F• 220 F to 170 F = Tender Zone

300F MTV 280F Screed 280F-220F Break down 220F-170F Tender 170F-150F Finish

BTU to AirBTU to Air BTU to Air BTU Air and Ground Grease to Glue 1Point Density UP

Continuously monitor the mix temperature all during the work day utilizing PAVE-IR. Keep an Infra-red hand held temperature gun on the finish roller to stay out of the Tender Zone

Truck Interruption STOP PAVING

• Paver@40fpm = 200ft pattern in 5 minutes

• 78F surface + 300F mix = 10 minute dwell time before rolling, the pave can stop

• Paver stop normal equal <20ft

• 5 paver stops@20ft =100ft

• Waiting on truck, slowly lay a 200ft rolling pattern@10fpm = 20 minute to lay the 200ft pattern…No Density

Roadway/Mix TemperaturesStation 127+60 Noncompacted

Time < 5 minCompacted Time <10 min

Delta Temperature Differential

MeasuredDensity Actual

Mix in Auger 300F 95.7 %

Pave-IR 297F scanning head

Gun - IR 295F 242F 53F

Middle Mat F. 298F 265F 33F

Bottom Mat F. 150F 221F 71F

Mix was laid 3:50 before the roller start and complete

10.5 minutes

Environmental Conditions = 78.5F surface 5 MPH wind

Hot Mix has to raise existing Mat degree F Up to >220F Above the Tender Zone

Be Consistent • MTV paving

• Uniform paving speed 30-40 FPM

• Uniform Temperature across the mat

• Uniform Rolling Pattern

• YIELDS 100% PAY !!

Rollers

• Run Matched rollers we run 3 Cat 534 XW, all having matched frequency and amplitude

• Density is a function of having a roller with enough weight, so that once it sets the mix in motion by the frequency and amplitude from the roller drum, it can seat the mix in place and produce a STABLE water impervious mat

Roller Stay in Their Wheel Path

Utilize Echelon rolling to cover the entire 12 foot travel lane in one pass

The Pave IR has shown that we laid a uniform pavement. It is now necessary to roll it uniformly to seal in the heat, and remove air voids

Mix Temperature• Major effect

on compaction

• Must compact while oil is still fluid enough to allow aggregate movement

My View of Future…Pave-IR• Mount a Pave-IR scanner forward on the paver

hopper to monitor the existing roadway pavement temperature

• The existing rear facing Pave-IR linked together with the forward Pave-IR and a computer will select the optimum paving speed in FPM

• The linked Pave-IR/Computer will be Bluetooth connected to the initial rollers running a mapping software. Any detected Thermal Segregated area will provide an exact location for the rollers to slow down and apply extra rolling energy to obtain density

My View of Future of Pave-IR

Dual Pave-IRs working in conjunction with Mapping software will identify Thermal Segregated Areas for extra compaction.

Intelligent Paving

• True remixing MTVs shall be used on all surface mixes

• Pavers can stop paving and not effect final density based on surface temperature

• Pave-IR allows the paving crew to self correct bad practices

• Future: Intelligent Pave-IR will allow for thermal scanning and roller mapping

March 22-24, 2016 | Nashville, TN | www.worldofasphalt.com

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