Erwin Kohler

Findings from the Tire/Pavement Noise Study at the UC Pavement

Research CenterPart of Caltrans Quiet Pavement Research (QPR) program

San Luis Obispo, CAJuly 23rd, 2007

Quieter Pavement Research

1. What properties/materials impact pavement noise levels and how?

2. How long can the acoustic benefits of the pavement last?

3. How do quieter pavements perform over time with regard to friction, smoothness, traffic loading, and maintenance needs?

Three QPR components: • flexible pavement,• rigid pavement (including bridge decks), and • acoustic correlation research

Purpose is to answer:

UCPRC QPR Experiment Design

• 80 pavement sections throughout California– 23 “Environmental” sections– 57 Regular sections

Pav. Type

Age

Rainfall

Traffic H L H L H L H L H L H L H L H L H L H L H L H L H L H L H L H L H L H L H L H L H L H L H L H L

DIS

T/C

TY/R

TE/K

P

03-P

LA-8

0-1.

4/2.

601

-LAK

-29-

R37

.3/R

37.6

04-C

C-6

80-2

3.9/

24.9

05-S

CR

-152

-7.6

/8.0

04

-Mrn

-101

-0.0

/2.5

(NB&

SB)

04-S

on-1

21-3

.4/7

.3(N

B&SB

)(+)

04-S

Cl-2

37-R

3.8/

7.10

(+)

08-S

Bd-3

8-S0

.0/R

5.0

04-M

rn-3

7-12

.1/1

4.4(

EB&W

B)(+

)01

-ME

N-1

-0.1

/15.

2 (S

tant

ec/c

ored

)04

-SC

l-237

-R1.

0/2.

303

-Sac

-16-

6.9/

20.7

03

-Pla

-80-

14.3

/33.

301

-MEN

-20-

R37

.9/4

3.0

06-T

UL-

99-4

2.0/

47.0

06-T

UL-

63-1

9.8/

R30

.1

03-S

ac-5

0-16

.10/

17.3

010

-Am

a-49

-14.

7/17

.607

-LA-

710-

6.8/

9.7

06-T

ul-6

5-21

/29

(Sta

ntec

/cor

ed)

04-N

ap-1

28-5

.1/7

.4 (E

.B. o

nly)

04-S

Cl-8

5-1.

9/4.

708

-SB

D-5

8-R

0.0/

5.3

01-M

EN-2

0-R

37.9

/43.

004

-SC

l-280

-R0.

0/R

2.7

06-T

UL-

63-1

9.8/

R30

.1

04-M

rn-1

01-1

8.9/

23.1

(NB

only

)04

-Son

-1-0

.0/8

.4 (N

B&S

B)(+

)08

-Riv

-15-

33.8

/38.

405

-SLO

-46-

R10

.8/R

22.0

04-M

rn-1

01-2

.5/8

.5 (a

s-bu

it)10

-Cal

-4-0

/18.

807

-LA-

60-R

25.4

/R30

.5(s

tant

ec)

07-V

en-3

4-4.

3/6.

3

01-M

EN-2

0-R

37.9

/43.

006

-FR

E-99

-10.

7/15

.907

-LA-

138-

60.2

/61.

6 03

-ED

-50-

17.3

/18.

303

-ED

-50-

18.5

/20.

3 (a

s-bu

ilt)

06-K

ER-9

9-R

29.5

/R31

.0 (o

nly

SB)

04-S

OL-

113-

0.1/

18.0

04-S

M-2

80-9

.6/1

0.8

01

-Men

-1-2

0.8/

38.7

(S

tant

ec/c

ored

)04

-Ala

-92-

6.6/

8.8

06-K

ER

-65-

R0.

0/2.

9 (S

tant

ec/c

ored

)01

-Lak

e-20

-45.

8/46

.501

-Men

-101

-37.

4/38

.801

-Men

-101

-50.

8/ 5

1.5

01-H

UM

-101

-111

.1/1

11.5

01-M

en-2

0-21

.19/

21.6

901

-Men

-20-

22.1

8 /2

2.68

H H H

L H H

H L H L H L H L H L H L H L H L

-4 year-8 year

H L H L H L H L

<1 year 1-4 years 5-8 years <1 yea

F mixes

<1 year 1-4 years 5-8 years <1 year 1-4 years 5-8 years <1 year 1-4 years 5-8 years

RAC-O RAC-GOGAC DGAC

Pavement types

Type Description Open? Rubber ? # of sections

DGAC Dense Graded AC 0 0 18

OGAC Open Graded AC 1 0 18

RAC-G Rubberized AC, Gap graded ? 1 13

RAC-O Rubberized AC, Open graded 1 1 20

F-mix special mix, northern CA 1 0 5

Data collection

Collect Cores

Friction (microtexture)

Permeability

Condition Survey

Macrotexture

Smoothness (IRI)

Pavement/ tire noise

Aggregate Gradation (sizes)

Sound absorption

Air Void Content

Thickness

Traffic closureTraffic speed Laboratory

Cores #1 and #2 Cores #3 and #4 Cores #9 and #10 Cores #11 and #12

Core #3

Core #4

Core #5

Core #6Friction and permeability

zones

Center of the lane

Wheelpath

Direction of traffic

25m between cores

3.6m

150m long test section

Cores #5 and #6 Cores #7 and #8

Detail segment

Work in a traffic closure

Traffic Control: Caltrans Maintenance

Condition survey: cracks & distresses, pictures

Cores: drill, extract, label, backfill

Friction: BP (& DFT)

Permeability: epoxy seal, place, pour water, time

Laboratory workAir void content Absorption

Aggregate gradation

OBSI, SRTT conversion

Aquatred vs SRTT Comparison

0

2

4

6

8

10

12

1497 98 99 10

0

101

102

103

104

105

106

107

108

More

0

2

4

6

8

10

12

14

97 98 99

100 101 102 103 104 105 106 107 108More

y = 0.9286x + 5.067R2 = 0.9645

90.0

92.0

94.0

96.0

98.0

100.0

102.0

104.0

106.0

92.0 94.0 96.0 98.0 100.0 102.0 104.0 106.0 108.0

Aquatred

SRTT

Aquatred

SRTT

~2.44

Ranges (histogram)

0

5

10

15

20

0.5 3.5 6.5 9.5 12.5

Age

0

5

10

15

20

25

297 675 1052 1430 More

MPD,microns

0

5

10

15

20

3 7 11 16 20

Air Voids (%)

02468

101214

97 98 99 100 101 102 103 104 105

OBSI (SRTT)

QPR questions

• What properties/materials impact pavement noise levels and how?

1. Pavement type2. Age3. Air void4. Texture (MPD)5. Thickness

1 - Pavement type

A-W

eigh

ted

Soun

d In

tens

ity,

dB

(A)

DGACRAC-GRAC-OOGAC

107

106

105

104

103

102

101

100

Boxplot of A-Weighted Sound Intensity Levels

OGAC & RAC-O < RAC-G & DGAC

102.5 & 102.1 < 103.2 & 104.1 (Aquatred)102.3 < 104.1 ~1.8 dB reduction

18 20 13 18

2 - Age

A-W

eigh

ted

Soun

d In

tens

ity,

dB

(A)

Pavement TypeAge Category

DGACRAC-GRAC-OOGAC>41-4<1>41-4<1>41-4<1>41-4<1

107

106

105

104

103

102

101

100

Boxplot of A-Weighted Sound Intensity Levels

DGAC : highest OBSI OGAC & RAC-O : similar OBSIRAC-G :usually higher noise levels than open graded mixes, except when <1 year

Age

Age (years)

A-W

eigh

ted

Soun

d In

tens

ity

Leve

ls,d

B(A

)

14121086420

107

106

105

104

103

102

101

100

Age and pavement type

Age (years)

A-W

eigh

ted

Soun

d In

tens

ity

Leve

ls, d

B(A

)

14121086420

107

106

105

104

103

102

101

100

DGACF-mixOGACRAC-GRAC-O

TypePavement

Age

Age

A-W

eigh

ted

Soun

d In

tens

ity

Leve

ls, d

B(A

)

14121086420

107

106

105

104

103

102

101

100

01

CodePavement

Scatterplot of A-Weighted Sound Intensity Levels

3 – Air-voidsA

ir V

oid

Con

tent

(%

)

Mix TypeAge Categories

RAC-ORAC-GOGACDGAC>41-4<1>41-4<1>41-4<1>41-4<1

22.5

20.0

17.5

15.0

12.5

10.0

7.5

5.0

Air Void Content for Different Mixes at Different Ages

Air voids

AV Content (%)

A-W

eigh

ted

Soun

d In

tens

ity

Leve

ls, d

B(A

)

22.520.017.515.012.510.07.55.0

107

106

105

104

103

102

101

100

Air voids

AV Content(%)

A-W

eigh

ted

Soun

d In

tens

ity

Leve

ls, d

B(A

)

22.520.017.515.012.510.07.55.0

107

106

105

104

103

102

101

100

DGACF-mixOGACRAC-GRAC-O

TypePavement

Air voids

Air Void Content (%)

A-W

eigh

ted

Soun

d In

tens

ity,

dB

(A)

22.520.017.515.012.510.07.55.0

107

106

105

104

103

102

101

100

01

CodePavement

Scatterplot of A-Weighted Sound Intensity versus Air Void Content (%)

DGAC : Air voids reduce OBSIOGAC : it is already good, does not matter

4 – Texture (MPD)

MPD (microns)

A-W

eigh

ted

Soun

d In

tens

ity

Leve

ls,d

B(A

)

20001750150012501000750500

107

106

105

104

103

102

101

100

01

CodePavement

DGAC & OGAC : lower MPD is better smaller aggregates

MPD

AV Content (%)

MP

D (

mic

rons

)

22.520.017.515.012.510.07.55.0

2000

1750

1500

1250

1000

750

500

lower MPD is better but it’s achieved at the expense of air voids

5- Thickness

Surface Layer Thickness (mm)

A-W

eigh

ted

Soun

d In

tens

ity

Leve

ls, d

B(A

)

120100806040200

107

106

105

104

103

102

101

100

DGACF-mixOGACRAC-GRAC-O

TypePavement

Thickness

Surface Layer Thickness (mm)

A-W

eigh

ted

Soun

d In

tens

ity

,dB

(A)

120100806040200

107

106

105

104

103

102

101

100

01

CodePavement

Scatterplot of A-Weighted Sound Intensity vs Surface Layer Thickness

DGAC : insensitive to thickness (maybe louder with thickness)OGAC : unless greater than 55 to 60mm, thickness doesn’t matter

10 close-up pictures

Sections QP10 to QP20

Database rages

Age : 1 – 14 years

OBSI(SRTT) : 98 - 104 dBA

MPD : 300 – 1800 microns

Air void : 3 – 22 %

QP10 07VEN34W5.9

RAC-G

Age=5

OBSI (SRTT) = 101.8

MPD = 889

AV = 10.2

QP11 07LA60E26.3

DGAC

Age=7

OBSI (SRTT) = 101.9

MPD = 652

AV = 5.5

QP12 08SBD58E4.2

RAC-O

Age=5

OBSI (SRTT) = 99.9

MPD = 1346.8

AV = 19.3

QP13 08SBD38E2.2

OGAC

Age=5

OBSI (SRTT) = 100.1

MPD = 1291

AV = 17.7

QP14 08RIV15S33.7

RAC-G

Age=5

OBSI (SRTT) = 100.1

MPD = 849

AV = 11.6

QP15 07LA138E61.3

DGAC

Age=<1

OBSI (SRTT) = 100.9

MPD = 638

AV = 6.7

QP16 04ALA92E7.7

DGAC

Age= 14

OBSI (SRTT) = 102.4

MPD = 1059

AV = 9.1

QP17 10AMA49S16.4

RAC-O

Age= 3

OBSI (SRTT) = 101.7

MPD = 1287

AV = 18.3

QP18 10CAL4W15.6

RAC-G

Age= 6

OBSI (SRTT) = 102.7

MPD = 1466

AV = 9.9

QP19 05SLO46W21.0

RAC-G

Age= 4

OBSI (SRTT) = 99.9

MPD = 758

AV = 10.7

QP20 05SCr152E7.9

OGAC

Age= <1

OBSI (SRTT) = 101.7

MPD = 1255

AV = 21.6

Model for Sound Intensity (OBSI)

• Multicollinearity: Principal factor analysis & Principal Components Regression

OBSI = 101 - 1.26 (A) + 0.664 (B) - 0.352 (C) + 0.00262 (MPD)

• Factors- 1.26 A: “Flow Variables” [AV (%) , Cu , F.M. , Code, Thickness ]

+ 0.664 B: “Surface Roughness” [Raveling, IRI, Age]

- 0.352 C: “Durability” [IRI, Cracks, Age]

+ 0.00262 MPD

• R-Sq = 52.8%, all factors significant at 95% confidence level

Conclusions

• OGAC is quieter than DGAC (~2dB)• Increasing air voids reduces OBSI for DGAC. OGAC

insensitive.– Affects high frequencies

• Increasing MPD increases OBSI (stronger for OGAC)– Affects low frequencies

• Rubber inclusion did not have a noticeable effect

• 80 sections was a small sample for the number of variables considered in this study

• A model was developed

Practical Recommendation

• At this time, the best approach is to use thin layers of OGAC or RAC-O with small aggregates

– Thin. Lower cost– OGAC or RAC-O. Better than RAC-G (longer benefit).

Quieter than DGAC– Small aggregates

Lower air voids (but still open). Good for durabilityLower MPD. Good for noise reduction at low frequencies