Today, with the rapid expansion of highways, asphalt concrete pavement has become a popular choice and has developed comprehensive technological solutions centered around pavement structure, raw materials, construction techniques, and quality inspections. Engineering construction methods have seen significant improvements, and the technical and quality standards of some asphalt concrete pavements have reached or nearly matched international excellence. However, the quality of asphalt concrete pavement is constrained and affected by various factors including operator skills, raw materials, machinery, technical processes, environmental conditions, and the complexity and interconnectivity of the construction process. Therefore, an effective supervision system is crucial. As supervisors, construction companies should strictly adhere to approved plans and established standards to ensure well-organized and appropriate execution of projects.
Every single step in the pavement construction process directly impacts the overall quality of the pavement. Hence, meticulous oversight of each step is essential to guarantee the production of high-quality asphalt concrete pavement.
1. Mixing Asphalt Mixture:
During the mixing process, asphalt concrete can experience inconsistent quality or uncertainty. This instability is particularly challenging at mechanized construction sites. For instance, uneven temperatures in the mix or inconsistencies in the specification of raw materials can lead to variations in particle composition, altering flow values and porosity, which ultimately affects pavement quality. To address this, we perform daily extraction and screening tests and analyze the results to guide production adjustments. This includes adjusting the proportion of cold hoppers and regulating the specifications of oscillating screens in the mixing plant. Based on practical experience, using circular hole screens with the following specifications has proven effective:
1# sieve > (1?2) mm
2# sieve = ((larger particle size?5mm)/2) + (1?2) mm
3# sieve = 5 mm - (1?2) mm
4# sieve = 3 mm
This approach allows for moderate adjustments. Using a round hole screen with sizes of 33, 16, 6, and 3 mm has shown good results. Our professional engineering supervision team conducts daily inspections during the mixing process and immediately corrects any issues.
2. Rolling Processing Technology:
Rolling is a critical process for creating asphalt surfaces, ensuring the pavement's physical and mechanical properties meet design requirements. Our supervision guidelines are implemented at all levels, and immediate corrections are made when deviations occur. Other key considerations include:
1. After rolling, edges often show gaps, which significantly impact the reliability of the pavement. Thus, careful monitoring of initial and final rolling temperatures is necessary to ensure compliance with design standards.
2. Oscillating rollers should not be started or braked abruptly on freshly laid surfaces. Experienced drivers should operate the equipment smoothly.
3. Excessive watering can cause the asphalt mixture surface to cool rapidly, leading to cracks. Watering on the roller wheels should be minimal to avoid compromising the effectiveness of the rolling process.
4. Before using a pneumatic tire roller, check that all tires are undamaged and at equal pressure to prevent unevenness in the finished surface.
3. Penetration Surface Layer Construction:
The construction of an asphalt penetration surface layer follows specific steps:
1. Plan and construct curbs.
2. Prepare the subbase.
3. Apply a permeable oil or tack coat to the surface.
4. Lay the main layer of aggregate, ensuring uniform particle size distribution and checking loose-laying thickness. Vehicles should not drive on newly laid aggregate.
5. Compact the main layer of aggregate using a 6-8 ton oscillating roller at 2 km/h. Roll from the edge towards the center, overlapping wheel tracks by 30 cm. Repeat the process from the opposite side. After rolling, check the road crown and adjust as needed. Roll twice to stabilize the aggregate. Use a 10-12 ton oscillating roller (or 12-15 tons for thicker surfaces), overlapping wheel tracks by more than half, and roll 4-6 times until the aggregate is tightly embedded without visible wheel tracks.
4. Asphalt Concrete Mixing:
Follow these rules when mixing asphalt concrete:
1. Strictly control mineral and asphalt usage according to the gradation sheet.
2. Monitor the heating temperatures of raw materials and asphalt.
3. Ensure uniform mixing without clumping or separation.
4. Sample each batch for testing asphalt characteristics, mineral gradation, and asphalt usage.
5. Clean mixing machinery after each shift, document checks, and prohibit non-compliant asphalt concrete from leaving the plant.
5. Sampling and Testing:
Construction site tests often yield variable results. To ensure accuracy:
1. Sample asphalt concrete using the statistical method to measure the gradation of asphalt mixtures. Sample from the hot mixer and paving site. Density tests require samples from compacted pavement, with immediate corrective action if discrepancies arise.
2. Sample every 500 tons of mix for review.
3. Conduct parallel tests for various indicators to verify results.
6. Paving Quality:
Pavement quality depends heavily on paving operations. Issues include uneven thickness, double slopes, and uneven paving rates. Solutions include:
1. Improve the planarity and elevation of the base layer to compensate for irregularities.
2. Adjust screed temperature and thickness to maintain uniform paving.
3. Match the feeder and paving rate to avoid material accumulation.
4. Maintain a consistent paving rate of 3-4 m/min to minimize stops and avoid wave patterns.
5. Address crawler contamination and transport vehicle impacts to ensure smooth paving.
7. Joint Treatment:
Joints can damage pavement flatness. To improve quality:
1. Cut joints with a saw to create a sloping surface.
2. Use a three-meter straightedge to check and remove defective sections.
3. Gradually roll joints from cold to hot, filling with coarse material until the required standard is met.
4. Level structural joints with a line and fill with thick material, ensuring skilled workers complete the task quickly.
5. Inspect and prepare the base layer at joints to ensure proper compaction and surface finish.
By addressing these aspects, we ensure high-quality asphalt concrete pavements that meet design and performance standards.
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