I. Light first, then heavy

Light rolling first

• Stabilizes the mixture initially and prevents shoving, bulging, and cracking.

• Increases density gradually, avoiding structural damage, loose surface, and aggregate crushing caused by heavy rolling at the beginning.

Heavy rolling later

• Further improves density to meet the designed compaction requirements.

• Compacts on a stable basis, resulting in higher efficiency and better quality.

One sentence: Light rolling first stabilizes and prevents deformation; heavy rolling later achieves density and strength.

II. Slow first, then fast

Slow rolling first

• Ensures uniform compaction without missing areas, tearing, or shoving.

• Provides sufficient time for material densification to guarantee compaction quality.

Fast rolling later

• After the temperature drops and the material stabilizes, the speed can be appropriately increased to improve construction efficiency.

• Only performs smoothing and final rolling without affecting density.

One sentence: Slow rolling first ensures uniformity and quality; fast rolling later improves efficiency without negative effects.

III. Standard answer template

Rollers follow the principle of light first, then heavy; slow first, then fast during rolling:

• Light first, then heavy: Light rolling is used first to stabilize the mixture, prevent shoving, cracking and loosening; heavy rolling is then applied to increase density and ensure compaction strength.

• Slow first, then fast: Slow rolling is used initially to ensure uniformity, avoid missing compaction and damaging the pavement structure; the speed is increased appropriately later to improve construction efficiency on the premise of ensuring quality.