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Asphalt Issues
TRB Committee AFK10March 17, 2004
Brian EganGary Head
Current Emphasis Areas
RAP Quality Control Fatigue Characteristics of HMA mixtures containing RAPNon-nuclear density devicesPavement SmoothnessNCAT Test TrackWhat Mix design/Compaction equipment to use?Performance testingEffect of CAA on Rutting Performance
Recycled Asphalt Pavement (RAP)
TDOT Specifications §307.03RAP... by cold planing is allowed...• A mix 15%• B-M, B-M2,
C-W, C 20%** except if uniform quality, then 20% does not apply, but 65% virgin asphalt
RAP- Quality Control
RAP- Quality Control
New Specification• A mix 15% (same)• BM, BM-2, C, C-W 20%• but if crushed or screened, and
sized such that the largest RAP particle is less than the nominal aggregate size of the mixture then can utilize 25% and C-S 15%• Must have 65% virgin AC
Fatigue Characteristics of HMA mixtures containing
RAP Currently evaluating the effects of RAP on the fatigue life of TDOT “D” mixes (surface)• 0, 10, 20, and 30% RAP w/PG 64 and 76• Limestone and Gravel Coarse Agg.• 4 different tests- (beam fatigue, indirect tensile strength,
semi-circular bending test (notched)
• Final report- fall/winter 2004• Phase 2- Field Evaluation funding
Approved
RAP testing
Evaluation of NonEvaluation of Non--nuclear density device nuclear density device
Preliminary FindingsPreliminary Findings
Backscatter GeometryBackscatter Geometry
Top Layer EffectTop Layer Effect
80%
60%
Our Findings…so farOur Findings…so far
Linear Regression of Corrected Nuclear Guage Values Vs. PQI Values
y = 0.9524x + 7.3249R2 = 0.935
120.0
130.0
140.0
150.0
160.0
120 130 140 150 160
Nuclear Guage (pcf)
PQI (
pcf)
Pavement Smoothness
5 high speed road profilersCorrelation between Mayes meter to develop new spec.Before and After with thin lifts
411 C BEFORE AND AFTER STUDYAVERAGE IMPROVEMENT: 33.3%
0
20
40
60
80
100
120
140
160
0 100 200 300 400 500
HCS IR
I (IN
/MI)
BEFOREAFTER%IMPROVEMENT
TDOT 2003
TDOT placed three tests sections August 12-15, 2003• SMA• OGFC on BM-2 at 75 gyrations• “D” mix with gravel at 75 gyrations
What is our future going to be?• SMA • OGFC • Marshall• Superpave (Gyratory compactor)
Why OGFC or SMA ?
95
96
97
98
99
Open graded Stone MatrixAsphalt
Dense GradedAsphalt
MeasuredTire Noise,
dB(A)
Compactive Effort Comparison
TDOT/Industry study; compare compactive efforts between Marshall and Superpavegyratory compactor (SGC)D and BM-2 mixes• 5 D-mixes• 3 BM-2 mixes
Comparison Plot
Air Voids versus Asphalt Content
0.01.02.03.04.05.06.07.0
3.5 4.0 4.5 5.0 5.5 6.0
Asphalt Content
Void
s in
Tot
al M
ix
75 Gyrations75 Blow Marshall65 Gyrations
Superpave gyration levels
Lowvolume
Highvolume
Comments
Georgia 65 80 SMA and OGFC onInterstate
Alabama 65 80 50 gyr. SMA on IS(and OGFC)
Mississippi 65 85 50 gyr. Superpaveif <1 mill ESAL
Virginia 65 75
Tennessee 65 ?? 75 ??
Performance Testing
Using Compaction study and APA data developed SP 407 SGC4 projects/ 1 per region- July 25, 2003 letting Mixture design with SGC at 65 gyrations and APA performance
Performance Testing
Specification Requirements:ADT <10,000• max. rut 0.40 in.
ADT >10,000• max. rut 0.35 in.
Did NOT change any aggregate requirements
PG 64-22 Rut Depths at 4,000 & 8,000 Cycles
0
0.1
0.2
0.3
0.4
0.5
0.6
Rut D
epth
(inc
hes)
4,000 Cycles 8,000 Cycles
53% ↑
47% ↓
0.40 in
PG 70-22 vs. APA Cycles
0
0.1
0.2
0.3
0.4
0.5
0.6
Rut D
epth
(inc
hes)
4,000 Cycles 8,000 Cycles
29%↑
71% ↓
0.35 in.
PG 76-22 vs. APA Cycles
0
0.1
0.2
0.3
0.4
0.5
0.6
Rut D
epth
(inc
hes)
4,000 Cycles 8,000 Cycles
32% ↑
68% ↓
0.35 in.
APA rut depths
0
0.1
0.2
0.3
0.4
0.5
0.6
Mixture 1 Mixture 2 Mixture 3 Mixture 4
Rut D
epth
, in.
DesignPlantCore
Effect of CAA on Rutting Performance
Proposed research project recently approved for fundingObjective: • What is the minimal level of CAA/
fractured faces needed• Evaluate different gravels with
varying % of fractured faces
Thank You .... Questions ????