Roller Pattern & Compaction Equipment Flashcards

What is the term used to describe the overlap of successive roller passes to ensure full coverage of the mat width?

Answer: Pass increment

A pass increment (or lane offset) defines how far the roller moves laterally between passes to ensure the entire mat width receives consistent compactive effort.

When compacting a superpaved mix with a nominal maximum aggregate size of 19 mm, what is the recommended maximum loose lift thickness?

Answer: 3 times NMAS (≈ 2.25 in)

A general rule of thumb is that loose lift thickness should not exceed 3 times the NMAS to ensure aggregate interlock and adequate compaction throughout the lift.

A pneumatic tire roller is MOST effective for which compaction task?

Answer: Kneading and sealing the surface after intermediate rolling

Pneumatic tire rollers are best at intermediate and finish rolling where their kneading action seals the surface and fills voids without displacing the partially cooled mix.

What minimum temperature (°F) is typically recommended for breakdown rolling of a PG 64-22 mix?

Answer: 275°F

Breakdown rolling for a PG 64-22 mix should begin while the mat is still above approximately 275°F to allow adequate workability and density achievement.

Which of the following BEST describes the 'echelon paving' technique and its effect on compaction?

Answer: Multiple pavers paving adjacent lanes simultaneously to keep the joint hot

Echelon paving uses multiple pavers operating side by side so the longitudinal joint between lanes is compacted while both sides are still hot, yielding higher joint density.

What roller defect can occur when the vibratory frequency is set too high relative to roller travel speed?

Answer: Chatter marks or washboard surface texture

When frequency is too high relative to roller speed, the drum strikes the mat too frequently in a short distance, creating a repeating indentation pattern known as chatter or washboard marks.

An inspector is checking compaction with a nuclear gauge near the centerline of a freshly compacted lane. The reading is lower than expected. Which roller pattern error is MOST likely?

Answer: The roller made fewer passes at the centerline than at the edges

Insufficient pass count near the lane centerline is a common pattern error that results in a density trough in the middle of the mat.