1. Implementation of the Pave-IR System in Texas
Russel Lenz, P.E.
TxDOT Construction Division
Division Director
Virginia Beach
August 3, 2011

2. Background
Historically, segregation (both physical & thermal) has been a major contributor to premature failures in flexible pavements with HMA surfaces.
TxDOT’s 2004 Standard Specifications attempted to address these concerns by requiring thermal and density profiles and by restricting paving when the surface temperature is below 60°F (70°F for SMA - 50°F for unmodified binders).
Many TxDOT districts also required the use of MTVs (shuttle buggies) to mitigate the problem.
Method of measuring thermal segregation with a hand held infrared thermometer proved to be relatively ineffective.
For the past 10 years, TxDOT has been working with TTI to develop a better methodology to measure thermal segregation.
TxDOT is now implementing the Pave-IR system developed by TTI and manufactured by Moba Corp.

3. TxDOT Definition of Thermal Segregation
Moderate
Severe
>25°F to 50°F
>50°F
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4. Pave-IR Output Showing Thermal Segregation (Truck End)
220
314
316
220
320
314
240
215
310

5. How TxDOT Specifications Address Segregation
A minimum of one “Thermal Profile” is required on every sublot of HMA. (Thermal profiles are 150 ft. in length.)
A “failing” thermal profile requires an additional density profile. Failing is defined as > 25°F thermal segregation.
No QC/QA bonus is paid if there is “severe” thermal segregation.
A “Density Profile” is required a minimum of once on every sublot. (11 density gauge readings taken 5 ft. apart in a line parallel to paving direction)
And every time the paver stops
And at locations where thermal segregation is identified
And where visible segregation is identified
Contractor waives QC/QA bonus if profile fails
Remove and replace sublot if it fails the density profile and has severe thermal segregation.
Note: density profiles are never required and are not applicable if the Contractor opts to use the Pave-IR system.

6. Implementation of the Pave-IR System
Goal: Improved pavement performance by encouraging Contractors to improve paving operations
Optional for use on TxDOT HMA paving projects
TxDOT specifications incentives
No density or thermal profiles
Opportunity to pave at lower temperatures (down to 32°F if dry)
Potential QCQA bonuses not waived for non compliance to density profile or thermal segregation requirement

7. Implementation of the Pave-IR System
TxDOT specifications incentives (cont’d)
Used in lieu of an MTD – End dumps not allowed w/o MTD
Automated documentation
Contractor’s ticket taker not required to measure mix temperature and record station # on haul tickets
Other minor incentives included in specification

8. Thermally segregated locations holding water.
Thermal Segregation - Background
Historically segregation thought of as mechanical (gradation) phenomenon
1996 – WSDOT discovered thermal imaging could detect segregation
Cold spots became low density areas
89 percent of locations with ∆t > 25°F failed density uniformity criteria
Thermal segregation work began as agencies were becoming more concerned with uniformity and paver stops. The density differential test was one outcome of agencies trying to obtain more uniform pavements and reduce the amount of paver stops.
Thermally segregated locations holding water
(courtesy WSDOT) 8

9. Example of a Density Profile (in pcf)
Note: TxDOT allows a maximum differential of 6 pcf from high to low or 3 pcf from low to average.
Research conducted by University of Connecticut, Connecticut Advanced Pavement Laboratory

10. NCAT (2000) and TTI (2002) similarly found thermal uniformity suitable for detecting segregation
NCAT – low severity segregation when ∆t > 18°F
TTI – when ∆t > 25°F, TxDOT density uniformity requirements not met 10

11. Why is Thermal Segregation Important?
Cold spots typically indicate low density areas
Density is “a” or “the” primary contributor to pavement performance
Contractor and agency risk are impacted
Acceptance and pay schedules are based on density
Segregated locations distress prematurely
Ride quality ultimately impacted by thermal segregation

12. Early observations: coarser texture and holding water
Common Performance Problems
Early observations: coarser texture and holding water

13. Raveling and Cracking Follow

14. Fatigue Life Substantially Reduced
Even moderate (>25 but < 50 F) thermal segregation can result in substantially reduced pavement life.
Source: NCAT (2000) 14

15. Common Methods of Measuring Thermal Segregation
Infrared Thermometers – less than $200
Infrared Cameras – less than $5K
Pave-IR System – less than $30K

16. Measuring Thermal Segregation
Test Method Tex-244-F
Handheld IR thermometer
Thermal camera
Pave-IR

17. Current Usage of Pave-IR
Texas – 25+ Units
Other users:
Minnesota
Wisconsin
NCAT
Other interested regions:
Washington
Alaska
Quebec
Ohio
Michigan
Germany
China
As of September 2010 these are the current users, and agencies/regions that have expressed interest in demonstrations 17

18. Test Device Strengths Weaknesses
Handheld IR Thermometer
Inexpensive.
Simple to use.
Tests independent of paving train.
Requires constant operator attendance.
May miss localized defects. No permanent record.
IR Camera
More coverage than thermometer.
May miss localized defects. No permanent record (usually).
Pave-IR
Does not require constant operator attendance.
Provides real-time feedback.
Tests virtually full-coverage.
Automated data reduction. Permanent record.
Most costly device.
Testing coverage could impact risk of finding defects.
May include artificial cold spots in data set.

19. Pave-IR Summary Results Screen
Summary Results during Data Collection
Press the button to view summary results
**Emphasize how to interpret this screen, what is important for inspector, and how to interpret the status bars…
The summary results first shows thermal segregation results for all profiles collected thus far in the data file. The top half of the results table presents these results. Each 150’ segment is analyzed to determine its temperature differential, then the results are summarized according to the number and percent of profiles containing moderate and severe thermal segregation. The categories are color-coded green, yellow, and red for no, moderate, and severe thermal segregation, respectively, and this status bar is color-coded according to the percentages in each category.
The lower half of the table defaults to present the result from the most recent profile. However, using the cursor buttons, the user may scroll through each individual profile to review the individual temperature differentials. Selecting to view the Results Summary Options will display which sensors are ignored from the analysis. Data collection continues as normal while reviewing summary results. Touching the checkmark will return to the data collection screen.
Pave-IR Summary Results Screen 19

20. Example report from project with minimal thermal segregation
The color plot shows ~ 750 feet of paving, with minimal thermal variations.
The report contains project information, a summary of the segment length, threshold temperature differential, and which sensors were ignored, then a thermal profile summary all on the first page. Subsequent report pages present summaries of locations with and without thermal segregation, a cumulative frequency distribution of measured placement temperatures, and locations of paver stops greater than one minute.
** Emphasize what is important for inspector – 0 “severe” and a nominal percentage “moderate” is good 20

21. Note report pages 3 & 4 are just continuations of profiles without thermal segregation21

23. Example report from project with severe thermal segregation

25. Next Slide All circumstances require NO reporting of test results
(or when Pave-IR is used
for informational only)
Use of
Pave-IR
YES
Measure temperature of HMA &
document with Station #
on each haul ticket
Next Slide
Comply with
pavement surface
temperature requirements
Perform density profiles
Paver stops
Thermal segregation
Visibly segregated areas
1 per sublot
Perform Thermal profiles
1 per sublot
Handheld thermometer
Thermal camera
Pass
Fail
Temperature
differential
< 25ºF
Moderate
thermal segregation
Thermal differential °F
Severe thermal
segregation
Thermal differential
> 50°F
When Moderate Thermal Segregation (25°F – 50°F) is Detected
If Contractor uses hand held thermometer or thermal camera for specification compliance: Take corrective action and:
Perform a density profile at the location thermal segregation was detected
If density profile fails – contractor waives QCQA production and placement bonus
If density profile passes – QCQA bonus if applicable will be paid provided contractor provides all documentation of thermal and density profiles
When Severe Thermal Segregation (> 50°F) is Detected
If Contractor uses hand held thermometer or thermal camera for specification compliance
Suspend operation & take immediate corrective action
No applicable QCQA bonus will be paid for production or placement if severe thermal segregation is identified
If density profile fails – Contractor must remove and replace the sublot
Report
test
results
Subject to:
No production &
placement bonuses
Remove & replace with
surface irregularities
Corrective action
Suspension of
paving operations
Pass
Immediate
Corrective
action
Subject to:
No production &
placement bonuses
Suspension of
paving operations
Immediate corrective
Action
Perform density profile
Remove & replace with
failing density profile
Report
test
results
Perform
density profile

26. Previous Slide Use of Pave-IR YES Provide Engineer electronic
(or when Pave-IR is used
for informational only)
NOT required to measure &
document HMA temp
and station # on each
Haul ticket
Allowed to pave
when roadway is dry &
surface temperature
is at least 32°F
Thermal
profile
Density profiles
NOT
required
Specify use for spec
compliance
Review output daily
Provide Engineer output files daily
Modify
paving process
Moderate
thermal segregation
thermal differential °F
Pass
Severe thermal
segregation
> 50°F
Subject to:
Suspension of
paving operations
Provide Engineer electronic
copies of all daily data files
Temperature
differential
< 25ºF NO
When Moderate Thermal Segregation (25°F – 50°F) is Detected
If Contractor uses Pave-IR for specification compliance
Modify the paving process as necessary to eliminate any (moderate or severe) thermal segregation identified by the Pave-IR system.
No further action (density profile) required
QCQA bonus if applicable will be paid provided contractor provides automated documentation of Pave-IR output
When Severe Thermal Segregation (> 50°F) is Detected
Engineer may suspend operations if recurring severe thermal segregation is identified.

27. When Moderate Thermal Segregation (25°F – 50°F) is Detected
If Contractor uses hand held thermometer or thermal camera for specification compliance: Take corrective action and:
Perform a density profile at the location thermal segregation was detected
If density profile fails – contractor waives QC/QA production and placement bonus
If density profile passes – QC/QA bonus if applicable will be paid provided contractor provides all documentation of thermal and density profiles
If Contractor uses Pave-IR for specification compliance
Modify the paving process as necessary to eliminate any (moderate or severe) thermal segregation identified by the Pave-IR system.
No further action (density profile) required
QCQA bonus if applicable will be paid provided contractor provides automated documentation of Pave-IR output

28. When Severe Thermal Segregation (> 50°F) is Detected
If Contractor uses hand held thermometer or thermal camera for specification compliance
Suspend operation & take immediate corrective action
No applicable QC/QA bonus will be paid for production or placement if severe thermal segregation is identified
Perform a density profile at the location thermal segregation was detected
If density profile fails – Contractor must remove and replace the sublot
If Contractor uses Pave-IR for specification compliance
Engineer may suspend operations if recurring severe thermal segregation is identified.
No further action (density profile) required
QC/QA bonus if applicable will be paid provided contractor provides automated documentation of Pave-IR output.

29. Conclusions “What Gets Measured Gets Done”
TxDOT, along with Industry, is implementing better specifications and better techniques to address the problem of thermal segregation
The Pave-IR System is an excellent “Passive Inspection” device that allows end result versus method specifications
It allows contractors to see what they are doing and improve their operations
Contractors can focus on causes and cures
Every contractor that has used the Pave-IR system states that they have improved their paving process from the feedback they get from the system.
“What Gets Measured Gets Done”

30. Questions? Russel W. Lenz, P.E. Director, Construction Division
(512)
Dale A. Rand, P.E.
Construction Division, Flexible Pavements Branch
(512)