The core goals of asphalt pavement compaction are to achieve qualified density (void ratio 3%-6%), excellent flatness (IRI ≤ 2.0m/km), and structural integrity protection. The combined selection of double steel drum and pneumatic tyred rollers must revolve around four core dimensions: "pavement structural layer characteristics, material type, construction environment, and quality requirements", and follow the principle of "divided work with coordination and complementary advantages". Specifically, double steel drum rollers focus on "vibratory compaction + flatness correction", while pneumatic tyred rollers focus on "kneading compaction + bonding enhancement". The specific logic for formulating selection criteria is as follows:
Before formulating combined selection criteria, it is necessary to first define key boundary conditions to avoid blind matching:
Pavement structural layer: Thickness (4-12cm) and design compaction requirements of the lower layer (load-bearing layer), middle layer (transition layer), and upper layer (functional layer, including ultra-thin wearing course).
Asphalt mixture type: Dense-graded AC, gap-graded SMA, open-graded OGFC, as well as aggregate gradation (coarse aggregate content 30%-70%), asphalt grade (70#/90#), and modifier type (SBS/rubber powder).
Construction environment: Temperature (5-35℃), wind speed (≤5m/s), base course flatness (IRI ≤ 3.0m/km), and working width (3-6m).
Quality control focus: Whether to emphasize rutting resistance, water damage resistance, or special requirements (such as appearance protection of colored asphalt).
Core advantages: The rigid steel drum can transmit high-frequency impact force through vibration, enabling rapid arrangement and compaction of mixture particles. The small contact area of the steel drum concentrates pressure, which can correct local protrusions/depressions on the pavement and ensure flatness.
Applicable scenarios: Initial compaction (leveling and static compaction), re-compaction (vibratory compaction), and final compaction (static rolling for finishing). Especially suitable for mixtures with high flatness requirements and relatively coarse aggregates.
Key parameters: Tonnage (8-14t), amplitude (0.3-0.8mm), frequency (30-40Hz), and static linear load (250-350N/cm).
Core advantages: The elastic pneumatic tyres provide uniform contact pressure (0.7-1.0MPa). Through "kneading and squeezing", they make mixture particles interlock more tightly and fill small voids left by the vibration of double steel drum rollers. Meanwhile, they can promote the bonding between asphalt film and aggregates, improving the pavement's rutting resistance.
Applicable scenarios: Re-compaction stage (cooperating with double steel drum rollers). Especially suitable for dense-graded AC, SBS-modified asphalt mixtures, or mixtures with high coarse aggregate content that are prone to voids.
Key parameters: Tonnage (16-22t), number of tyre sets (3-5), and tyre pressure (0.6-0.8MPa). It is necessary to ensure that the tyres are free of damage and have clear patterns.
Core requirements: High-strength compaction, stable aggregate interlocking, and providing support for the upper layer.
Combination scheme: Double steel drum roller (12-14t) + pneumatic tyred roller (18-22t).
Division logic:
Initial compaction: Double steel drum roller performs static rolling for 2 passes at a speed of 2-3km/h to level the mixture and stabilize the loose-laid layer, avoiding displacement.
Re-compaction: First, the pneumatic tyred roller rolls for 3-4 passes at 3-4km/h to fully interlock coarse aggregates and fill voids through kneading; then the double steel drum roller performs high-frequency, small-amplitude vibratory rolling for 2-3 passes (frequency 35-40Hz, amplitude 0.5-0.8mm) to enhance deep compaction.
Final compaction: Double steel drum roller performs static rolling for 2 passes at 3-4km/h to eliminate wheel tracks and correct flatness.
Selection basis: The lower layer has a large thickness and coarse aggregates. Kneading by the pneumatic tyred roller solves the void problem between coarse aggregates, while the vibration energy of the heavy-tonnage double steel drum roller can penetrate to the bottom of the layer, avoiding "dense surface and loose interior".
Core requirements: Uniform compaction, smooth transition, and balancing strength and flatness.
Combination scheme: Double steel drum roller (10-12t) + pneumatic tyred roller (16-18t).
Division logic:
Initial compaction: Double steel drum roller performs static rolling for 1-2 passes at 2.5-3.5km/h to quickly stabilize the loose-laid layer.
Re-compaction: Pneumatic tyred roller rolls for 2-3 passes + double steel drum roller performs vibratory rolling for 2 passes (frequency 32-38Hz, amplitude 0.4-0.6mm) to balance compaction density and uniformity.
Final compaction: Double steel drum roller performs static rolling for 1-2 passes to eliminate re-compaction wheel tracks.
Selection basis: The middle layer has a medium thickness and does not require extra-heavy equipment. The combination of medium-tonnage double steel drum and pneumatic tyred rollers avoids aggregate crushing caused by over-compaction while ensuring interlayer bonding.
Core requirements: High flatness, anti-skid performance, water damage resistance, and avoiding surface damage.
Combination scheme:
Conventional AC-13: Double steel drum roller (8-10t) + light pneumatic tyred roller (16t).
SMA-13 (gap-graded): Mainly double steel drum roller (8-10t); pneumatic tyred roller is optional (tyre pressure must be reduced to below 0.6MPa to avoid damaging the fiber stabilizer).
OGFC-13 (open-graded): Only double steel drum roller (8t) is used; pneumatic tyred roller is prohibited (to avoid clogging voids).
Division logic:
Initial compaction: Double steel drum roller performs static rolling for 1 pass at 2-3km/h, with temperature controlled above 150℃ (above 160℃ for modified asphalt) for rapid leveling.
Re-compaction: For AC-13, add 1-2 passes of pneumatic tyred rolling (for kneading compaction), then 1-2 passes of high-frequency, small-amplitude vibratory rolling with double steel drum roller (amplitude 0.3-0.5mm, frequency 38-40Hz); for SMA-13, directly use double steel drum roller for 2 passes of vibratory rolling to avoid aggregate skeleton damage by pneumatic tyred roller.
Final compaction: Double steel drum roller performs static rolling for 2 passes at 3-4km/h, completed when the temperature drops below 90℃ to ensure no wheel tracks.
Selection basis: The upper layer has a small thickness and high functional requirements. Light double steel drum rollers avoid over-compaction. Pneumatic tyred rollers only assist in dense-graded mixtures. For SMA/OGFC, special structures need protection, so pneumatic tyred rollers are prohibited or used with caution.
Dense-graded AC (uniform aggregates, small void ratio): Priority is given to the "double steel drum + pneumatic tyred" combination. Kneading by the pneumatic tyred roller further reduces void ratio and improves durability.
SBS-modified asphalt mixture (high viscosity, strong toughness): The tonnage of the pneumatic tyred roller can be appropriately increased (18-20t), and the amplitude of the double steel drum roller is set to 0.4-0.6mm. High-frequency vibration promotes the flow and compaction of the mixture.
Rubber asphalt mixture (high elasticity, strong bonding): Increase the number of rolling passes of the pneumatic tyred roller by 1-2, and raise the vibration frequency of the double steel drum roller to 35-40Hz to enhance the bonding effect.
Open-graded OGFC (void ratio 15%-25%): Only static rolling + low-frequency, small-amplitude vibratory rolling with double steel drum roller is used. Pneumatic tyred roller is prohibited (rubber on tyres is easy to adhere to the mixture and block drainage voids).
High-temperature environment (temperature ≥ 30℃): Reduce the tonnage of the pneumatic tyred roller by 1-2t, increase the rolling speed by 0.5-1km/h to avoid mixture sticking to tyres and displacement; reduce the amplitude of the double steel drum roller by 0.1-0.2mm to prevent over-compaction.
Low-temperature environment (temperature 5-10℃): Use heavy-tonnage pneumatic tyred roller (20-22t) + medium-tonnage double steel drum roller (10-12t), increase re-compaction passes by 1-2, and raise the frequency of the double steel drum roller to 38-40Hz. Use vibration energy to compensate for insufficient fluidity of the mixture at low temperatures.
High-wind environment (wind speed 3-5m/s): Reduce the use of pneumatic tyred rollers (to avoid rapid cooling and hardening of the mixture surface, which reduces kneading effect). Focus on vibratory compaction with double steel drum rollers and shorten the rolling interval.
Narrow spaces (e.g., tunnels, interchange ramps): Use small double steel drum roller (6-8t) + small pneumatic tyred roller (14-16t) to ensure operational flexibility, with unchanged combination logic.
Compaction pass control: 1-2 initial compaction passes, 3-5 re-compaction passes (pneumatic tyred + double steel drum), 1-2 final compaction passes, with a total of 5-9 passes. Adjustments are made based on compaction test results (each additional pass increases compaction by 0.5%-1%).
Speed-temperature matching: Initial compaction speed 2-3km/h (mixture temperature 130-160℃), re-compaction speed 3-4km/h (temperature 110-140℃), final compaction speed 3-4km/h (temperature 90-110℃). The rolling speed of pneumatic tyred rollers is slightly 0.5km/h higher than that of double steel drum rollers.
Equipment quantity ratio: Calculate based on a working width of 3-6m. Each paver is matched with 1 double steel drum roller for initial compaction + 1-2 pieces of equipment for re-compaction (double steel drum + pneumatic tyred) + 1 double steel drum roller for final compaction. Ensure continuous rolling (when the paver speed is 2-4m/min, the following distance of rollers ≤ 5m).
Quality verification standards: Compaction ≥ 96% (for expressways), flatness IRI ≤ 2.0m/km, no obvious wheel tracks on the surface (depth ≤ 2mm), and no defects such as displacement, peeling, or aggregate crushing.
Taboos: Using heavy-tonnage double steel drum rollers (≥12t) for vibratory rolling on the upper layer, which easily causes surface cracking and reduced flatness; using pneumatic tyred rollers for SMA/OGFC rolling, which easily damages the aggregate skeleton or clogs voids.
Misunderstandings: Using only double steel drum rollers without pneumatic tyred rollers makes it difficult to reduce the void ratio of dense-graded mixtures to the design requirement, resulting in insufficient rutting resistance; using only pneumatic tyred rollers without double steel drum rollers fails to ensure pavement flatness and easily causes wavy deformation.
Avoidance methods: Clarify the mixture type and structural layer function before selection; assign equipment functions according to the logic of "stable initial compaction, sufficient re-compaction, and flat final compaction"; verify the combination scheme through a test section (length 200-300m); adjust tonnage, passes, and rolling sequence based on compaction and flatness test results.
The combined selection criteria for double steel drum and pneumatic tyred rollers essentially represent a systematic decision-making process of "defining functions by structural layer, determining strength by material, and making adjustments by environment". For the lower layer, "compaction depth" is emphasized, requiring a heavy-tonnage combination; for the middle layer, "balanced adaptation" is emphasized, requiring a medium-tonnage combination; for the upper layer, "functional protection" is emphasized, requiring a light combination or a single double steel drum roller combination. The core is to form complementarity between the "vibratory compaction + flatness" of double steel drum rollers and the "kneading compaction + bonding" of pneumatic tyred rollers, ultimately achieving the quality goals of asphalt pavement.
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