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 ????