Question

The endurance limit for an asphalt concrete mix in tension is 0.000758 strain. a pavement structure is designed to limit the tensile strain at the bottom of the asphalt layer to 0.000720 strain. How many traffic repetitions will be needed to cause fatigue cracking in the asphalt concrete layer? Explain your answer.

Answer 1

By fatigue cracking model

3.89( 10.854 Nf 2.21 10-

Where,

Nf = No. of cumulative standard axles to produce 20% cracked surface area

$\varepsilon _{t}$ is strain at the bottom of Bituminous Concrete layer =0.000720

E is elastic modulus of asphalt at 32 F = 20,00,000- 50,00,000 psi

considering E = 50,00,000 psi = 34473.78 MPa

1 0.854 1 3.89 Nf 2.21 10.00 34473.78 0.000720

f 10705.81