Question

5. Name the two types of fatigue cracking and the critical pavement locations.

Type:                              Critical location:    

Type:                                Critical location:

6. Name the causes typically associated with both types of fatigue cracking.

First Type:                             Causes:

Second Type:                         Causes:          

7. Name the type of loading typically used in the laboratory for evaluating:

Thin pavements        :          

Thick pavements       :          

8. In a typical conventional asphalt concrete pavement, keeping all other factors constant, (FILL IN THE BLANKS)

1. Increasing the HMA thickness typically                        fatigue cracking.

2. Increasing the HMA modulus typically                         fatigue cracking.

3. Increasing the wheel load typically                                fatigue cracking.

4. Increasing the tire pressure typically                             fatigue cracking.

Answer 1

• Fatigue cracking are of two types: critical pavment location:

1) bottom up fatigue cracking    1) bottom of HMA layer

2) top down fatigue cracking 2) top in areas of high tensile stresses

• causes typically associated with both types of fatigue cracking

1) bottom up Causes:- Due to generation of high tensile stresses under    repeated loading .

2) top down Causes:- Due to generation of high localised tensile stresses from tyre pavement interaction and asphalt binder aging.

• Type of loading typically used in the laboratory for evaluating thick and Thin pavements are Alf (accelerated loading facility ).  

• In a typical conventional asphalt concrete pavement, keeping all other factors constant, (FILL IN THE BLANKS)

Increasing the HMA thickness typically DECREASE fatigue cracking.

Increasing the HMA modulus typically INCREASES  fatigue cracking.

Increasing the wheel load typically INCREASES fatigue cracking.

Increasing the tire pressure typically INCREASES fatigue cracking.

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