DEVELOPMENT OF INFRARED AND RADAR TECHNOLOGIES FOR IDENTIFYING MIXTURE

SEGREGATION

Rick Collins (TxDOT)

Background to Thermal Segregation

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

.

Thermally segregated locations holding water

(courtesy WSDOT)

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

y = 0.2415xR2 = 0.9027

-15

-10

-5

0

5

10

15

-60 -40 -20 0 20 40 60

Change in Temp (F)

Cha

nge

in D

ensi

ty (p

cf)

Spec max density differential = 6 pcf

6 pcf density differential at ~ 25 F

temp differential

Implementing IR into Specifications Existing methods

using handheld IR devices already in place

Pave-IR system developed through research collects full-coverage testing without operator attendance

Moba Corporation refined and now manufactures Pave-IR. This device is commercially available

Thermal profile and results available real time Desktop software for viewing data files and

generating pdf report

Thermal Profile View in Operacion Summary Results in Operacion

Reviewing Thermal Profile with Desktop Software

Implementing IR into Specifications

In 2010 the use of Pave-IR is now included in TxDOT Special Provision 341-024

Pave-IR automatically processes data and generates report

Currently 12 Pave-IR systems purchased by Contractors and in use in Texas

Background to Ground Penetrating Radar

Sends pulses into pavement – non contact and high speed

Reflections obtained at interfaces of materials with different electrical (dielectric) properties

Traditionally used for thickness estimates and locating subsurface defects and section changes

Using GPR for Evaluating HMA Construction

TxDOT has extensive experience using GPR and an active GPR program

In-house software for data processing

The amplitude of the Surface reflection is related to density of the HMA surface layer

Plan Profile View of expected Air Void Distribution

Using IR and GPR Together IR serves well as QC with real-time

monitoring GPR serves as a QA check on completed

projects

IR Bar Installed in a PaverGPR Collecting Data