When a road roller compacts an asphalt pavement, temperature is a core variable that determines compaction quality. Excessively high temperatures can easily cause the asphalt mixture to shift and bleed, while excessively low temperatures make it impossible for particles to fully interlock (asphalt hardens and compactness is insufficient). It is necessary to strictly follow the principle of "stage-by-stage temperature control and dynamic adaptation", and accurately control the temperature around the three core stages of initial compaction, re-compaction, and final compaction in combination with environmental conditions. The specific requirements are as follows:

I. Division by Compaction Stages: Clarify Temperature Ranges and Core Requirements for Each Stage

The three stages of asphalt pavement compaction have different goals (stabilizing pressure, achieving density, and finishing for flatness), and the corresponding temperature requirements vary significantly, requiring strict control stage by stage:

1. Initial Compaction Stage: "High-Temperature Stabilization and Shaping" – Sufficiently High Temperature Required

The core of initial compaction is to fix the shape of the mixture through light compaction, preventing material displacement and accumulation during subsequent rolling. This must be completed when the asphalt still has good fluidity, so the temperature requirement is the strictest.

Temperature Range:

• Ordinary Hot-Mix Asphalt Mixture (e.g., AC type): The starting temperature for initial compaction must be ≥ 130℃ (petroleum asphalt has low viscosity, and this temperature ensures fluidity).

• Modified Asphalt Mixture (e.g., SBS, SBR modified): The starting temperature for initial compaction must be ≥ 150℃ (modified asphalt has higher viscosity, and a higher temperature is required to avoid "wheel adhesion" or displacement during rolling).

• Stone Mastic Asphalt (SMA): The starting temperature for initial compaction must be ≥ 160℃ (SMA contains a large amount of coarse aggregate; high temperature ensures that the asphalt mastic fully fills the gaps between aggregates, preventing voids in later stages).

Key Operational Requirements:

Initial compaction must closely follow the paver (distance ≤ 10m). Especially in low-temperature and windy weather, the temperature drop rate of the mixture can reach 5-10℃/min, and delays will cause the temperature to quickly drop below the lower limit. If the initial compaction temperature is insufficient, the mixture will have hardened, and rolling may easily cause "bulging in front of the wheel" (material accumulation) or "surface cracks". In such cases, rolling must be stopped immediately; later, only high-frequency vibration during re-compaction can barely make up for the defect (with an effect far worse than normal initial compaction).

2. Re-Compaction Stage: "Medium-Temperature Intensive Compaction for Density" – Temperature Balances Efficiency and Effect

Re-compaction is the core link to improve the compactness of the asphalt surface course. It relies on high-frequency vibration (double-drum roller) or flexible kneading (pneumatic tire roller) to expel air from the mixture. The temperature must ensure that the asphalt still has plasticity while avoiding excessive displacement.

Temperature Range:

• Ordinary Hot-Mix Asphalt Mixture: The starting temperature for re-compaction is ≥ 110℃, and the ending temperature is ≥ 70℃.

• Modified Asphalt Mixture: The starting temperature for re-compaction is ≥ 130℃, and the ending temperature is ≥ 90℃.

• Stone Mastic Asphalt (SMA): The starting temperature for re-compaction is ≥ 140℃, and the ending temperature is ≥ 100℃.

Key Operational Requirements:

Temperature must be dynamically monitored during re-compaction: In hot weather (ambient temperature > 30℃), the ending temperature can be appropriately relaxed (e.g., ordinary asphalt can continue to be compacted until it drops to 60℃). In low-temperature and windy weather (ambient temperature < 10℃), the rolling speed must be increased (e.g., from 3km/h to 3.5-4km/h) to ensure that the required 4-6 rolling passes are completed before the temperature drops below the lower limit. Forced rolling at excessively low temperatures (e.g., ordinary asphalt < 70℃) is strictly prohibited. At this point, the asphalt has hardened, and rolling cannot improve compactness; instead, it will cause aggregate crushing and surface sanding, directly affecting pavement strength.

3. Final Compaction Stage: "Low-Temperature Finishing for Flatness" – Temperature Not Lower Than the Lower Limit for Wheel Track Elimination

The core of final compaction is to eliminate vibration wheel tracks left by re-compaction and improve pavement flatness. No additional compaction is required, so the temperature must ensure that the asphalt still has slight plasticity to eliminate wheel tracks without damaging the surface structure.

Temperature Range:

• Ordinary Hot-Mix Asphalt Mixture: The starting temperature for final compaction is ≥ 80℃, and the ending temperature is ≥ 50℃.

• Modified Asphalt Mixture: The starting temperature for final compaction is ≥ 100℃, and the ending temperature is ≥ 70℃.

• Stone Mastic Asphalt (SMA): The starting temperature for final compaction is ≥ 110℃, and the ending temperature is ≥ 80℃.

Key Operational Requirements:

Final compaction must use static rolling (vibration turned off for double-drum rollers) or pneumatic tire rollers to avoid "cracking" of the surface layer due to high-frequency vibration at low temperatures. If the final compaction temperature is below the lower limit (e.g., ordinary asphalt < 50℃), wheel tracks can no longer be eliminated. Forced rolling will cause "indentation cracks" on the pavement; later, only thin-layer repair can improve the condition (with poor aesthetics and durability).

II. Temperature Adjustment Under Special Environments: Addressing Weather Effects on Temperature

The temperature of the asphalt mixture is greatly affected by the environment. Low temperatures, strong winds, and rain accelerate temperature drop, requiring targeted adjustment strategies to avoid substandard compaction quality:

1. Low-Temperature Weather (Ambient Temperature < 10℃)

• Increase Initial Temperature: Require the asphalt mixing plant to increase the delivery temperature of the mixture (10-15℃ higher for ordinary asphalt, 15-20℃ higher for modified asphalt) to offset temperature loss during transportation and paving.

• Shorten Operation Intervals: Reduce the distance between the paver and the initial compaction roller to 5-8m, and conduct re-compaction and final compaction continuously to avoid intermediate pauses (a 1-minute pause may cause a 5-8℃ temperature drop).

• Reduce Paving Width: Reduce the single paving width from 6-8m to 4-5m to reduce the exposed area of the mixture and lower the temperature drop rate.

2. Windy Weather (Wind Speed > 5m/s, approximately Force 3 Wind)

• Install Thermal Insulation Devices: Add a thermal insulation cover behind the paver's screed and wrap thermal insulation cotton around the roller's drums to reduce the cooling effect of wind on the mixture and drums.

• Accelerate Rolling Rhythm: Increase the re-compaction and final compaction speed by 0.5-1km/h (e.g., from 3km/h to 3.5-4km/h) to complete the required number of rolling passes before the temperature drops rapidly.

• Prioritize Compacting Leeward Sides: If there are obvious wind gaps in the section (e.g., bridges, open areas), first compact the leeward area, and handle the windward side after the wind speed decreases to avoid sudden temperature drops on the windward side.

3. Rainy Weather (Light Rain or Heavier)

• Prohibit Construction: Rainwater will damage the adhesion between asphalt and aggregates; even if the temperature meets the standard, spalling and water seepage may occur in later stages. If light rain suddenly falls during construction, stop paving immediately, use the roller to quickly compact the already paved section (combining initial compaction and re-compaction within the allowable temperature range), and cover it with a rainproof cloth to prevent rainwater from seeping in.

III. Temperature Monitoring and Testing: Avoid Subjective Judgment Errors

Judging temperature based solely on "hand feel" or "appearance" is error-prone. Professional tools must be used for real-time monitoring to ensure data accuracy:

Testing Tools:

The core tool is an insertion thermometer (measurement range 0-200℃, accuracy ±1℃), which must be inserted into the mixture to a depth of ≥ 50mm (to avoid only measuring surface temperature, as the surface temperature is 5-10℃ lower than the internal temperature). An infrared thermometer is used as an auxiliary tool to quickly measure surface temperature and predict temperature drop trends, but it cannot replace the core testing function of the insertion thermometer.

Testing Frequency:

Measure once every 50m of paving before initial compaction (taking the average of 3 points each time), measure once after each rolling pass during re-compaction, and measure once before final compaction. A dedicated person must record the testing time, location, and temperature value to form a "Temperature Testing Record Form", which serves as a basis for quality traceability (e.g., if rutting or water seepage occurs on the pavement in later stages, it can be checked whether it is caused by substandard temperature).

IV. Handling of Common Temperature-Related Issues

• If the mixture shifts or bulges during initial compaction, it is mostly due to excessively high initial compaction temperature (e.g., ordinary asphalt > 160℃). The solution is to lower the delivery temperature of the mixing plant or slow down the paving speed to allow the temperature to drop to a reasonable range before rolling.

• If the compactness is insufficient after re-compaction, it is mostly due to excessively low re-compaction temperature (e.g., ordinary asphalt < 70℃). For subsequent construction, increase the delivery temperature, shorten the rolling interval, or increase the number of re-compaction passes when the temperature meets the standard.

• If obvious wheel tracks remain after final compaction, it is mostly due to excessively low final compaction temperature (e.g., ordinary asphalt < 50℃). The solution is to increase the starting temperature of final compaction or speed up the final compaction to prevent the temperature from dropping below the lower limit.

• If surface bleeding occurs (abnormal gloss), it is mostly due to excessive asphalt overflow caused by high temperatures during initial or re-compaction. The solution is to lower the rolling temperature or reduce the kneading time of the pneumatic tire roller (to avoid excessive rolling causing asphalt to float upward).

In summary, temperature control for road roller compaction of asphalt pavements essentially involves "completing operations at each stage within the 'compactable range' of asphalt" – temperatures above the upper limit easily damage the structure, while temperatures below the lower limit prevent sufficient compaction. Dynamic adjustments must be made based on stage goals and environmental conditions, and professional monitoring must be used to ensure accurate temperature control. Only in this way can the compactness, flatness, and durability of the asphalt surface course be guaranteed.