CTE Pavement Design & Materials

Question 1

In AASHTO pavement design, what does the structural number (SN) represent?

Accepted Answer

An index reflecting the structural strength of a pavement to support traffic loads

Answer

The number of axle load repetitions a pavement can sustain

Answer

The thickness of the asphalt surface layer in inches

Answer

The subgrade resilient modulus value

Question 2

What is the primary distress mode that MEPDG (Mechanistic-Empirical Pavement Design Guide) predicts for flexible pavements?

Accepted Answer

Alligator fatigue cracking, longitudinal cracking, and rutting simultaneously

Answer

Only alligator cracking

Answer

Transverse thermal cracking only

Answer

Faulting at transverse joints

Question 3

What is the Equivalent Single Axle Load (ESAL) concept used for in pavement design?

Accepted Answer

Converting mixed traffic of different axle weights into equivalent 18-kip single axle loads for design purposes

Answer

Measuring actual truck axle weights at weigh stations

Answer

Calculating pavement deflection under live loads

Answer

Setting legal load limits for highway vehicles

Question 4

What does the California Bearing Ratio (CBR) test measure?

Accepted Answer

The resistance of a subgrade or base material to penetration, used to assess pavement support strength

Answer

Asphalt mix stiffness at high temperatures

Answer

Concrete compressive strength for rigid pavement design

Answer

Aggregate gradation compliance for base course

Question 5

In flexible pavement design, what is 'rutting' and what layer is most often responsible?

Accepted Answer

Permanent surface deformation in wheel paths; most often caused by the asphalt surface or intermediate layer

Answer

Cracking at joints; caused by the base layer

Answer

Transverse cracking; caused by thermal expansion

Answer

Edge cracking; caused by inadequate shoulder support

Question 6

What is the purpose of the Performance Grade (PG) binder specification system developed under SHRP?

Accepted Answer

Grading binders based on climate-specific high- and low-temperature performance limits

Answer

Classifying asphalt binders by penetration depth at 77°F

Answer

Specifying viscosity requirements for warm-mix asphalt

Answer

Defining RAP content limits for recycled mixes