9A. Sampling, testing, evaluation, and soil stabilization techniques

Question 1

Causes of alligator (bottom-up fatigue) cracking.

Answer 1

1. Loss of base, subbase or subgrade support (poor drainage)
2. Stripping on the bottom of the HMA layer
3. Increase loading (unanticipated loads)
4. Inadequate structural design
5. Poor construction (inadequate compaction)

Question 2

Causes of longitudinal (top-down) cracking for rigid pavement.

Answer 2

Poor lane joint construction
Temperature cycling
Reflective cracking in base layer
Volume changes in subgrade

Question 3

Causes of rutting (permanent deformation).

Answer 3

Heating/cooling cycles in the asphalt. (i.e., surface cools faster and with more intensity than the core of the structure)

Question 4

What are the distress in rigid pavement?

Answer 4

Bottom-Up Transverse Cracking (JPCP)
Top-Down Transverse Cracking (JPCP)
Joint Faulting (JPCP)
Punchouts (CRCP)