Asphalt concrete paving
The quality of paving directly affects the overall quality of the pavement, so this becomes the focus of our supervision of the asphalt concrete pavement construction process. The quality of the paving operation is not only related to the performance of the machinery itself, but also depends on factors such as the continuity, stability and uniformity of the paving, as well as the balanced degree of material supply, so there are more problems that arise at this stage, such as.
(1) Uneven thickness of asphalt concrete pavement always exists objectively, which can cause different compaction effects produced by different thicknesses under the same paving coefficient and thus affect the pavement levelling. Therefore, in addition to improving the levelness and elevation control of the grass-roots level, the supervision of the levelness and elevation of the asphalt pavement of the following layer should also be strengthened to make up for it, and the layer by layer is strictly controlled up to the upper layer.
In extraordinary circumstances, to ensure the thickness of the pavement, appropriate elevation adjustments are taken to ensure the thickness of the structural layer of the pavement.
(2) A two-way slope will appear for some distance after the paver has been opened, which has a great impact on the pavement level. By repeatedly verifying the arch and screed self-weight sag and the size of the temperature difference between the screed pre-heating temperature and the river paving temperature.
Therefore, we require a temperature of not less than 80°C during screed preheating, levelling with a leveller and determining the thickness of the pivot plate under the screed (thickness of the pivot plate = thickness of loose paving + screed preheating arch + high level error of the subgrade, with five pivot points generally required). Especially when the whole paving, should be adjusted to the same slope before paving the arch, and timely adjustment, especially before paving stop to check, adjust well, in order to avoid the second joint when the road width bias high and low.
(3) Paver spiral paddle and paving walking speed mismatch, so that the paving room in the accumulation of too much or too little material, resulting in the screed under the mixture of coarse and fine away from the fold, we require the spiral paving room mixture material pile height flush in or slightly higher than the spiral paver axis line. In particular, the spiral paver is not idle phenomenon.
(4) The paver’s walking speed is not uniform, so that the paving speed is not uniform, and the asphalt pavement surface forms waves, which seriously affects the levelness and compaction. Therefore, we require that it should be guaranteed to travel at a speed of 3ˉ4m/min and avoid stopping as far as possible.
In the event of a stoppage, the paver screed should be locked in place so that it does not sink. Pause times should not exceed 10 minutes at temperatures above 10°C. If the pause is longer than 30 minutes or if the mix is below 100°C, re-joint according to the cold joint method. Ensure that at least three loads of material are waiting to be laid before the paver to minimise downtime and avoid the formation of waves.
(5) The following types of problems often occur in the stability of paver travel.
- Granular material withdrawn from the paver track driving line due to unloading is not removed in time, resulting in sudden changes in paving thickness. Therefore, during the construction process, the construction personnel are urged to inspect at all times in order to avoid this situation.
- The transport vehicle backing up when hitting the paver, causing the paver to twist forward, so that the road appears convex rash, we require in the continuous paver process, the transport vehicle should be in front of the paver 10ˉ30cm stop, and hang idle, rely on the paver to push slowly forward;.
(6) In the construction of the middle and upper layers, as the levelling beam (dragging bar) has high stiffness, low deflection, many landing wheels and sleds, reasonable distribution of its own weight and good walking stability, we therefore require that the levelling beam must be used, which has a good effect on improving the level and thickness of the road surface.
Asphalt concrete rolling
Rolling is the main process of asphalt surface forming, which is an important link to ensure the quality of the pavement so that its physical and mechanical properties and functional characteristics meet the design requirements, and is also the last process of asphalt pavement construction. We supervise the implementation of responsibilities in this area, follow the work and correct any inappropriate ones in time.
(1) At the end of rolling, the pavement often appears to be pushed and cracked, which has a great impact on the stability of asphalt concrete pavement.
Therefore, the rolling temperature of the initial and final compaction is tested in due course to ensure that the final compaction is within the design requirements.
(2) The roller is not allowed to start and brake quickly on the newly paved surface and requires skilled and experienced drivers to operate it.
(3) Spraying too much water causes the surface of asphalt concrete to cool too quickly, making the surface of the asphalt mix crack, so the water sprayed on the roller wheel should be strictly controlled, as long as it does not stick to the wheel, and affect the effect of the roller on the asphalt concrete rubbing.
(4) the use of tyre way roller before checking the wear and tear of the tyres and pressure is equal, to prevent the tyre on the soft and hard, affecting the transverse smoothness of the surface layer.
Sampling and testing
Site tests often appear to test the results and the actual difference between more, so it is required to do the following.
(1) asphalt mixture according to the statistical method of sampling, to determine the aggregate grade asphalt content, compaction aggregate sampling location in the asphalt mixer before the hot mix equipment, asphalt content test should be in the back of the paver and roller in front, from the paved mixture in the sample, compaction test should be taken from the pressed pavement concrete samples, get the test results, if there is a mistake immediately notify the mixing floor or paving site, and make the appropriate measures.
(2) Mix sampling is taken once for every 500T mixed, and the results are approved by us.
(3) When the construction unit to make a test of the indicators, their own good parallel test, in order to do their review of the use.
Joint treatment
Asphalt pavement joints are unavoidable operation interruptions and joints with the structure of the two cases, the joints part of the concentration of adverse factors affecting the smoothness of the pavement, its good or bad quality has a great impact on the quality of the pavement, in order to improve the quality of the joints must take the following measures:.
(1) The use of seam cutter to cut its section, to ensure that the joint section is a vertical surface.
(2) The position of the cut joints must be checked by a three-metre ruler, and all parts of the joint collapsed by the previous rolling must be removed.
(3) Rolling when the roller transverse rolling from cold to hot gradually transition, and repeatedly fill with fine material, until the three-metre straightedge check to reach the required standard, before starting longitudinal rolling.
(4) and the beginning of the joint with the structure seems to be the same as the cold joint, need to manually pave the terminal section to hang line level, fine material filling while rolling, to have skilled workers to operate, in a short time to complete, to ensure that the rolling temperature.
(5) and the structure of the joint before, first carefully check whether the joint at the grass-roots level, rolling is dense, how the degree of slab, from the multifaceted to ensure the smoothness of the rigid-flexible boundary.
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