Table 2.  Minimum Thicknesses and Material Requirements for Composite Pavements

2 

SUPERPAVE with Low ESALs 

3 

SUPERPAVE with Low ESALs 

3 

SUPERPAVE (4% voids) 

4 

SUPERPAVE (4% voids) 

The Highways Agency in the U.K. has extensive experience with composite pavement 

specifications, design, construction, and testing.  Composite pavements are commonly referred to 

as “flexible composite pavements.”  The design methodology and procedure used in the U.K. 

Pavement Design Guide is based on the TRL Report 615 (Nunn, 2004).   

The U.K. design method uses a nomograph to obtain two parameters: (1) the thickness of 

HBM base.  First, the foundation stiffness (modulus of resilience) is categorized based on the 

following ranges: 

•  Class 1 ≥ 50 MPa (7,252 psi) 

 10

•  Class 2 ≥ 100 MPa (14,503 psi) 

•  Class 3 ≥ 200 MPa (29,007 psi) 

•  Class 4 ≥ 400 MPa (58,015 psi) 

 

Second, the hydraulically bound base thickness is obtained as a function of the cement-

bound material (CBM) category described in Table 3. 

 

The properties of the base materials are shown in Table 4.  Once the thickness of the base 

is obtained, the thickness of the asphalt layer can be obtained from Equation 9. 

 

 

( )

(

)

( )

2

asphalt

H

16.05

L og N

101 L og N

45.08

= −

×

+

×

+

 

(9)

 

where 

 

 

H

asphalt

 = asphalt thickness (mm) (for 50 MSA < N < 80 MSA) 

 

N = cumulative traffic (MSA = million single axles = 1,000,000 ESALs). 

 

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