1. The compaction of the asphalt mixture should be completed as soon as possible after the paving is under high temperature.
2. When rolling, follow the principles of “high frequency, low amplitude, close follow, slow pressure, less water, high temperature”, “from outside to inside, from low to high”.
3. The road roller should adopt the method of high vibration frequency and low amplitude. When rolling, it should follow the paver forward and then return. The driving speed should be slow and uniform, and the amount of water sprinkling should be based on the non-stick wheel.
4. Compaction is divided into three processes: initial pressure, re-pressure, and final pressure. The purpose of initial pressure is to level and stabilize the mixture. The purpose of re-pressure is to make the mixture dense, stable, and shaped. trace, and finally form a flat compacted surface.
5. The compaction temperature, speed, and a number of passes should be adjusted according to the type and thickness of the asphalt mixture. Generally speaking, the optimum compaction temperature of the asphalt mixture is 120-140°C, and the optimum compaction temperature of the SBS asphalt mixture is 140～160℃, the rolling speed is controlled at 2～4km/h, and the tire roller can be increased appropriately, but not more than 5km/h.
Rolling of asphalt pavements by road rollers is an important part of road construction projects. How to successfully complete the compaction work determines the progress of the entire project.
We know that there are two factors that affect the compactness and flatness of asphalt concrete structural layers: compaction temperature and compaction method.
The compaction temperature is commanded and controlled by the on-site dedicated temperature test personnel to control the rolling time and rolling location.
Key points of the compaction method
1. Carry out in accordance with the principle of top-down, static first, then vibration, first slow, and then fast. The single rolling distance should be as long as possible, so as to fully exert the stability of the rolling force;
2. It is required that the road roller should be followed closely behind the paver for rolling, and it should not be too far away to prevent the temperature conditions from being out of control. Before the final rolling, all the wheel rails should be eliminated, and the operation should be stopped immediately after meeting the requirements to avoid excessive vibration;
3 The elimination of wheel rails can be carried out by overlapping rolling. During rolling, adjacent rolling belts overlap 1/3~1/2 of the wheel width and gradually move from the lower side of the cross-section to the higher side. One turn of the road roller is one pass of rolling;
4 If it is not on the same section as the direction of the paver, but is in a stepped shape, then it is necessary to stagger the distance back and forth each time it is rolled, usually half a meter is enough. The method of first long and then short is adopted, that is, the first rolling distance is long, and the subsequent distance is gradually shortened.
5. Pay attention to the amount of water sprayed by the nozzle of the road roller. It is advisable to use non-stick wheels. It is forbidden to turn, brake, or stop when the rolling process is not terminated.
The following six skills should be mastered in the construction of road rollers in order to achieve twice the result with half the effort:
01 First light then heavy
The choice of compaction machinery should be light first and then heavy. At the beginning, the soil is soft. If the tonnage of the road roller is too heavy, the soil will accumulate, the thickness will be uneven, and the degree of compaction will not be guaranteed. Therefore, first, use a light roller to compact the soil uniformly, and then use a heavy roller to compact the soil to the required degree of compaction after the subgrade soil has a certain strength. If it is a vibratory roller, the first pass should be static pressure, and then from weak vibration to strong vibration.
02 First slow and then fast
The compaction speed should be slow at first and then fast. The rolling speed of the road roller should gradually increase with the increase of the number of rolling times, that is, the initial rolling should be carried out at a lower speed, which can prolong the time of rolling pressure, increase the depth of influence, accelerate soil deformation, and avoid The phenomenon of rolling the wheel and filling the soil can be generated to prevent abnormal situations such as the road roller getting stuck.
As the number of rolling passes increases, the compactness of the paving layer also increases rapidly, and accelerating the rolling speed is conducive to improving the smoothness of the surface layer of the paving layer and improving the operating efficiency of the road roller.
03 Side first then center
Straight line sections and large curved road sections without superelevation should be edged first and then centered. The road roller rolls from the outside of the roadbed, along the extension direction of the roadbed, and gradually rolls toward the centerline of the roadbed to form a road arch for easy drainage.
04 Curves from the inside out
Small curved road sections with superelevation shall be rolled from the inside to the outside, from the lower part of the subgrade to the higher part of the subgrade, to form a one-way superelevation cross slope.
05 Drive wheel behind
The driving wheel of the road roller should be behind when rolling the slope. When going uphill, the rear driving wheels can bear the driving force provided by the slope and the machine itself, and at the same time, the front wheels initially compact the road surface to withstand the large shear force generated by the driving wheels.
When going downhill, the impact force generated by the roller’s own weight is offset by the braking of the driving wheel. Only the mixture rolled by the front wheel can support the rear driving wheel to generate shear force.
06 Avoid shaking in place
During operation, the road roller should start before starting to vibrate. When parking, it should stop vibrating first and then stop to avoid in-situ vibration.
Specific rolling steps
1 Initial pressure
The temperature of the initial pressure should be above 150°C, start the machine with a steel wheel roller for 1-2 times static pressure, and keep the speed within 2km/h and keep it fast. Rolling is carried out on a flat surface, the driving wheel is in front, that is, facing the paver, and the driven wheel is behind. In the case of a slope, whether it is uphill or downhill, the driving wheels are at the bottom.
2 Complex pressure
After the initial pressure is completed, re-compacting can be carried out. At this time, the temperature of the road surface should not be lower than 125°C. First, use a heavy-duty double-drum roller to vibrate and roll 4 times at a speed of 4km/h~5km/h, and then use a heavy-duty tire roller to roll. 6 times, keep the speed at 3.5km/h~4.5km/h. In the end, depending on the effect, the number of rolling times can be increased by 1 or 2 times.
3 Final pressure
Immediately after the re-pressing is completed, the final pressure is carried out. At this time, the temperature of the road surface is preferably above 110 °C. Turn off the vibration and carry out static rolling at a speed of 2km/h~3km/h.
What type of roller is used for asphalt?
What are the main types of asphalt pavement compaction machinery?
1) Double-wheel steel cylinder roller: 6~8t;
2) Three-wheel steel drum roller: 8~12t, 12~15t;
3) Tire roller: 12-20t, 20-25t;
4) Vibratory roller: 2～6t, 6～14t;
5) Walk-behind small vibratory roller: 0.8～1.5t;
6) Vibrating tamping plate: the mass is not less than 180kg, and the vibration frequency is not less than 3000 times/min;