Roller Pattern & Compaction Equipment Flashcards

Which type of roller is typically AVOIDED when compacting open-graded friction courses (OGFC)?

Answer: Pneumatic tire roller

Pneumatic tire rollers are not used on OGFC because their kneading action can clog the open-graded voids with binder, destroying the drainage characteristics of the mix.

What is the recommended direction for beginning the first breakdown roller pass on a newly paved lane?

Answer: From the high side of the mat toward the low side

Beginning on the high side (or centerline on a crowned road) and rolling toward the low side prevents the mix from being displaced downhill and ensures the mat is confined laterally.

What is 'tenderness' in an asphalt mix, and how should a roller operator respond to it?

Answer: A mix that is workable but prone to shoving; operator should reduce compactive effort and allow cooling

A tender mix is temporarily unstable and prone to shoving or rutting under roller load; the operator should reduce roller weight, turn off vibration, or wait for the mix to cool slightly.

A 3-axle tandem steel roller is used for finish rolling. Which statement about its operation is CORRECT?

Answer: It should operate in static mode to remove roller marks without displacing the mix

During finish rolling, static mode removes surface irregularities without risk of displacing the already-densified mix that is approaching its stiffness threshold.

How does increasing the number of passes on a nearly cooled mat (below 175°F) typically affect the compaction result?

Answer: Has little effect on density and may cause surface damage

Once HMA cools below approximately 175°F the binder is too stiff to be re-worked, so additional passes add minimal density while risking surface cracking or aggregate fracture.

What does the term 'roller pattern' specifically define in asphalt paving inspection?

Answer: The sequence, direction, speed, and number of passes the roller makes over the mat

A roller pattern documents the precise sequence of passes, directions, overlaps, speeds, and equipment settings used to achieve target density on a specific mix and lift.

Which instrument is commonly used in the field to evaluate compaction quality without coring?

Answer: Nuclear density gauge or non-nuclear density gauge (EDG/PQI)

Nuclear density gauges (and non-nuclear alternatives like the Pavement Quality Indicator) measure in-place density quickly to verify that compaction targets are being met.