Segregation is defined as a lack of homogeneity in the HMA mat of such magnitude that there is a reasonable expectation of accelerated pavement distress.

• A. It is a uniform distribution of aggregate materials.
• B. It is a lack of homogeneity that can accelerate pavement distress.
• C. It is caused by improper compaction alone.
• D. It is a temporary surface roughness phenomenon.

Answer: (B)

Segregation in asphalt pavement is an uneven distribution of materials within the hot-mix asphalt mat, which creates nonuniform properties across the pavement surface. When the mat isn’t homogeneous, some areas may have coarser aggregate or thicker binder films while others are denser or more fines-rich. This lack of uniformity leads to stress concentrations and weaker zones, making the pavement more susceptible to distress as traffic loads begin to accumulate. That’s why the definition emphasizes a lack of homogeneity large enough to reasonably expect accelerated damage—because those inconsistent zones behave differently under load, moisture, and temperature changes, hastening cracking, raveling, or rutting. The other ideas don’t capture the issue: a uniform distribution would not be segregation; segregation isn’t simply caused by compaction alone (it’s about material distribution within the mat, though improper compaction can worsen the effects); and it isn’t a temporary surface roughness phenomenon, which would imply transient irregularities rather than persistent, distress-inducing nonuniformity.