TxDOT’s Use of Permeable Friction Courses (PFC)

Dale Rand, P.E.

TxDOT Construction Division

Flexible Pavements Branch

Arkansas Asphalt Pavement

Association

January 6, 2006

TxDOT’s Mission StatementThe mission of the Texas Department of

Transportation is to provide safe, effective and efficient movement of people and goods.

The vision of the Texas Department of Transportation is to provide transportation systems and alternatives that are comfortable, safe, durable,

cost-effective, accessible, environmentally sensitive and aesthetically appealing.

TxDOT’s Vision Statement

TxDOT HMA Classifications,2004 Standard Specifications

• Item 340 Dense Graded Hot Mix Asphalt (Method)

• Item 341 Dense Graded Hot Mix Asphalt (QC/QA)

• Item 342 Permeable Friction Course (PFC)

• Item 344 Performance Design Mixtures

• Item 346 Stone Matrix Asphalt (SMA)

Type “D” Hot Mix

PFC

Why does TxDOT’s like SMA & PFC

Stone Matrix Asphalt (SMA)…..DurabilityHigh binder content and stone matrix offer the best combination of cracking and rutting resistance relative to other known mixes

Permeable Friction Course (PFC)….SafetyReduces risk of hydroplaningSignificantly reduces splash and sprayImproves visibility of traffic markingsQuieter than most other optionsImproved ride quality

Background

TxDOT used OGFC (plant mix seal) up until the early 1990sTxDOT ceased using OGFC in the early 90s due to durability issuesTxDOT started using PFC in 2000The use of PFC is growing at a steady rateThere are approximately 100 PFC projects completed or currently under construction in Texas

Comparison of Plant Mix Seal and Permeable Friction Course

< 20%N/A, > 30 % Cantabro Loss

1.25 to 1.5 inches1.0 inch or lessTypical thickness

HighModeratePermeability

0.0 Typical0.3% Maximum

0.5 – 1.5%Drain down

10 – 14 years5 – 8 yearsTypical life

300F – 350FRemoves all moisture

212F – 220FNot all moisture removed

Production Temperature

18% - 22%12% – 15%Air Voids

0.3 %Cellulose or Mineral

N/AFiber

6 – 7 % (PG 76)8 – 10% (A-R)

5 – 7%Binder %

PG 76-22Asphalt Rubber (A-R)

AC-10 AC-10 (+ 3% latex)

Binder Grade

Permeable Friction CoursePlant Mix SealCharacteristic

0-5

0-10

N/A

25-40

90-100

100

ODOTOGFC

1-4

N/A

5-10

10-25

35-60

90-100

Georgia1/2 inch

PEM

1-42-4N/AN/A#200

N/A N/A5-150-4#10

1-105-10N/AN/A#8

1-2015-255-200-8#4

35-6055-7550-8050-803/8 inch

80-10085-10095-10095-1001/2 inch

Texas1/2 inch

PFC PG76

Georgia1/2 inchModified

OGFC

TexasGrade 2

Plant Mix Seal

TexasGrade 1

Plant Mix Seal

SieveSize

OGFC – Gradation Comparison (% Passing)

Master Gradation Band (% Passing by Weight or Volume) and Binder Content

Sieve Size PG 76 Mixtures A-R Mixtures

3/4" 100.0 100.0

1/2" 80.0 – 100.0 95.0 – 100.0

3/8" 35.0 – 60.0 50.0 – 80.0

#4 1.0 – 20.0 0.0 – 8.0

#8 1.0 – 10.0 0.0 – 4.0

#200 1.0 – 4.0 0.0 – 4.0

Binder Content, %

5.5 – 7.0 8.0 – 10.0

@ 9 years - Asphalt Rubber - PFC

Lufkin District

Comfort

Ride quality Noise

US 287 (Wichita Falls District) International Roughness Index (IRI)

Comparison of 2 Projects Completed in the Fall of 2001

0

20

40

60

80

100

120

140

Reference Markers

IRI (

In./m

i.)

Flexible (PFC + Superpave) Rigid (11" CRCP)

0300 +00.5 to 0312 +00.0

0472 +01.2 to 0478 +00.2

US 287

US 70/ US 287Avg. IRI = 43

Avg. IRI = 90

% Energy Loss -Vs- dBA Reduction

20

37

50

60

7075

8085

8890

92 94 95 96 97 97.5 98 98.4 98.75 99

0

10

20

30

40

50

60

70

80

90

100

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Noise Reduction (dBA)

% S

ound

Ene

rgy

Loss

85%

Highway Safety

For most people, driving is the most dangerous activity that we are ever involved withBy 1950, more Americans were killed in auto accidents then were killed in both world warsA high percentage of accidents happen in intersections and in horizontal or vertical curvesWet weather accidents account for a high percentage of highway fatalities

How Can PFC Mixes Improve Safety?

Reduces the risk of hydroplaningDrains the water off the roadway quickerReduces sprayReduces glareImproves visibility of traffic markingsCoarse macro-texture improves frictional characteristics

Question: Can we prove that these things actually reduce the occurrence of wet weather accidents?

IH 35 – San AntonioPFC Overlay on Existing CRCP

A-R PFC on CRCP

IH 35 San Antonio, Fall 2002

IH 35 – San AntonioA-R PFC Overlay on Existing CRCP

Existing concrete pavement– Relatively sound structurally (Durable)– Approximately 20 years old (Durable)– History of numerous wet weather accidents (Safety?)– Ride Quality was poor (IRI = 200) (Comfort?)– Considered to be one of the loudest pavement

surfaces around (Comfort?)

A-R PFC Overlay on CRCPIH 35 San Antonio

1.5 inches of A-R PFC– Improved the ride quality of the existing CRCP by

approximately 61%– Improved the skid resistance by over 200%– Reduced the noise level by an average of 8 to 14

decibels (measured by 3 different individuals)– Significant reduction in major accidents after the PFC

overlay

Climatic & Accident DataIH 35 San Antonio: Before and After A-R PFC Overlay

July 2001-June 2002• Total Precipitation:

– 31.78 inches

• Total Days with…– Measurable precipitation: 69

• Major Accidents: 85• Major Accidents on Days

with Precipitation: 39

Nov 2003-Oct 2003• Total Precipitation:

– 32.63 inches

• Total Days with…– Measurable precipitation: 99

• Major Accidents: 48• Major Accidents on Days

with Precipitation: 19

Climate data obtained from National Oceanographic and Atmospheric Administration

Click on image below to show video

US 183 – Williamson Co.

South Bound near San Gabriel River

PFC Mix

Dense Grade (Type C)

Click on image below to show video

RM 1431 – Travis County

WBL – Between Cedar Park and Jonestown

PFC Mix

Dense Grade

RM 1431 – Travis County – Pictures from Feb 14, 2004

2001 – 2003: 124 Total Accidents

2001 – 2003: 68 Wet Weather Accidents

2001 – 2003: 6 Fatalities, 62 Injuries (13 incapacitating)

Note: Project length is only 2 miles long

Accident Data: FM 1431 - Travis County - Near Jonestown (PFC mixture was placed in February 2004)

Averages % ChangeYear 2001 2002 2003 2004 2001-2003 in 2004Total # of accidents 29 51 44 17 41.3 -58.9Dry weather accidents 10 23 13 15 15.3 -2.2Wet weather accidents 19 28 21 2 22.7 -91.2Fatalities 0 1 5 0 2.0 -100.0Total injuries 25 16 21 0 20.7 -100.0Incapacitating injuries* 6 4 3 0 4.3 -100.0Non-incapacitating injuries 19 12 18 0 16.3 -100.0Annual rainfall (inches) 42.9 36.0 21.4 52.0 33.4 55.5

Total rain days (>0.1 in.) 57 56 37 70 50.0 40.0

* Some of these injuries later became fatalitiesSource: Cedar Park Police Department

Safety is a Major Quality of Life Issue

Conclusions

TxDOT uses a variety of 4 different HMA mixturesGoal: Select the most appropriate mixture type for each given application The use of PFC and SMA is increasing in Texas due to the unique properties of these mixesPFC is considered to be the quietest and safest option currently available for paving

Thank You

TexasDepartment

of Transportation