Post on 22-Feb-2016
description
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