Material Properties

AASHTO Design Equation

1986

2

10

10 18 10 10 R

5.19

4.2 plog4.2 1.5log W 9.36log SN 1 0.20 2.32log M 8.0710940.4SN 1

ConstructedPavement Subgrade

Structural Number

1 1 2 2 3 3SN a D a D a D

1 2 3, , Ra a a Mf

3

asphalt base subbase

4

Typical Layer Coefficients

Subbase

Base

Asphalt

D2

D3

D1Dense-graded asphaltSand asphaltCrushed stone baseSandy gravel baseCement-treated baseAsphalt-treated baseLime-treated baseSandy gravel subbaseSand subbase

0.440.400.140.070.200.300.200.110.08

Typical Layer Coefficients

Pavement Stresses @ 24"

0

1

2

3

4

5

6

7

8

-6 -4 -2 0 2 4 6

Offset (ft)

Stre

ss (p

si)

Subgrade onlySubgrade + 24" SubbaseSubgrade + 6" Subbase + 18" BaseSubgrade + 6" Subbase + 12" Base + 6" Asphalt

5

Resilient Modulus

6

Resilient Modulus

Axial strain

Dev

iato

r stre

ss

MR

7

Diametral Resilient Modulus

8

Asphalt Layer Coefficient

9

Granular Soils

Source: WSDOT Pavement Guide Interactive CD-ROM 10

Base Layer

2 100.249log 0.977 BSa E

21 k

BSE k

11

AASHO Road Test

MoistureState

k1(psi)

k2(-)

Dry 8000 0.6Damp 4000 0.6Wet 3200 0.6

WARNING: We don’t actually use different values for different moisture states.This just illustrates the effects of moisture on base layer resilient modulus.

12

Estimating Base

Asphalt Thickness

(in)

Subgrade Resilient Modulus (psi)

3000 7500 15,000

< 2 20 25 302 – 4 10 15 204 – 6 5 10 15> 6 5 5 5

13

Base Layer Coefficient

14

CTB Layer Coefficients

15

ATB Layer Coefficients

16

Subbase Layer

3 100.227log 0.839 SBa E

21 k

SBE k

17

AASHO Road Test

MoistureState

k1(psi)

k2(-)

Damp 5400 0.6Wet 4600 0.6

WARNING: We don’t actually use different values for different moisture states.This just illustrates the effects of moisture on base layer resilient modulus.

18

Estimating Subbase

Asphalt Thickness

(in)

StressState(psi)

< 2 102 – 4 7.5> 4 5

19

Subbase Layer Coefficients

20

Drainage Coefficients

1966

21

1972

t

10

10 18 10

5

i

.19

4.2 plog4.2 1.5log W 9.36log SN 1 0.20 10940.

1log 0.372 S 3.

S 1

0R4

N

t10

10 18 10

5.19

4.2 plog4.2 1.5log W 9.36log SN 1 0.20 10940.4SN 1

1986

10

t10

10 18 10

5.19

R

4.2 plog4.2 1.5log W 9.36log SN 1 0.20 10940.4S

2.32log M 8.07

N 1

Drainage Coefficients

1 1 2 2 2 3 3 3SN a D a D m a D m

2 3, m m drainagef

22

asphalt base subbase

Drainage Quality

Quality Water Removed Within

Excellent 2 hoursGood 1 dayFair 1 weekPoor 1 month

Very Poor No drainage

23

Drainage Coefficients

Quality < 1% 1-5% 5-25% > 25%Excellent 1.40-1.35 1.35-1.30 1.30-1.20 1.20

Good 1.35-1.25 1.25-1.15 1.15-1.00 1.00Fair 1.25-1.15 1.15-1.05 1.00-0.80 0.80Poor 1.15-1.05 1.05-0.80 0.80-0.60 0.60

Very Poor 1.05-0.95 0.95-0.75 0.75-0.40 0.40

Percentage of Time Material Approaches Saturation

24

AASHTO Design Equation

1986

25

10

10 18 10 10 R

5.19

4.2 plog4.2 1.5log W 9.36log SN 1 0.20 2.32log M 8.0710940.4SN 1

ConstructedPavement Subgrade

Seasonal Moisture Effects

Time

Mod

ulus

Winter Freeze

Spring Thaw

Recovery

26

Seasonal Moisture Effects

27

WSDOT

28

Minnesota DOT

Season IWinter

Season IIEarly Spring

Season IIILate Spring

Season IVSummer

Season VFall

Description All LayersAre Frozen

Base Thaws,SG Frozen

Base Recovers,SG Thaws

HMA Low,SG Recovers

All LayersAre Standard

Pavement Layer Moduli Relative to Fall ValuesHMA High High Standard Low StandardBase High Low Low Standard StandardSG High High Low Low Standard

29

Minnesota DOT

Season IWinter

Season IIEarly Spring

Season IIILate Spring

Season IVSummer

Season VFall

Description All LayersAre Frozen

Base Thaws,SG Frozen

Base Recovers,SG Thaws

HMA Low,SG Recovers

All LayersAre Standard

Seasonal Modulus FactorsHMA 2.6 2.1 1.4 0.4 1.0BaseSG 22 2.4 0.73 0.75 1.0

30

AASHTO Design Equation

1986

31

10

10 18 10 10 R

5.19

4.2 plog4.2 1.5log W 9.36log SN 1 0.20 2.32log M 8.0710940.4SN 1

ConstructedPavement Subgrade

AASHTO Design Equation

32

10

10 18 10 10 R

5.19

4.2 plog4.2 1.5log W 9.36log SN 1 0.20 2.32log M 8.0710940.4SN 1

Q Ti

“i”representsablockoftimewithconstantMRItcouldbeamonth,aweek,aseason,etc.

10 18 18log 10 10 iTQii iW Q T W

“Standard” Vehicle

1 consumption per passageSS

dN

33

Seasonal Damage per ESAL

i

ii TQ Q

18 i

1 1 udW 10 10 10

i

8

i 2.32TR i

1 1.18 10u10 M

Let

di = damage per ESAL in Season i

34

Average Damage per ESAL

n n nf

i i i i i iQ Q Qi 1 i 1 i 1

1 1 1 1 1 ud f d f u f un n 10 10 n 10

fi = fraction of annual ESALs applied during Season i

35

Effective Modulus

8

f 2.32R eff

1.18 10uM

R 0.431eff

3005Mu

36

Example

Period MR ui N ui NDec-Feb 20,000 3

Mar 2500 1Apr-May 4000 2Jun-Nov 7000 6

37