With the continuous improvement of China's highway network construction, asphalt pavement is widely used in various transportation projects such as highways, urban main roads, rural roads, etc., due to its advantages of smoothness, comfort, wear resistance, skid resistance, and convenient construction. The paving construction of asphalt pavement is the core process that determines the quality of the pavement. The standardization of its construction technology and the degree of control over its technical points directly affect the smoothness, compaction, durability, and driving safety of the pavement. If the paving construction process is not standardized and the technical points are not properly controlled, it is easy to encounter problems such as road cracks, ruts, looseness, and substandard flatness. This not only affects the driving experience, but also shortens the service life of the road surface and increases the cost of later maintenance and repair.
The construction of asphalt pavement follows the core principles of "process standardization, parameter refinement, process traceability, and full quality coverage", which runs through the entire process of construction preparation, mixture mixing, on-site paving, rolling forming, and post maintenance. The core goal is to ensure that the paving quality meets the standards and create a smooth, wear-resistant, anti-skid, and durable asphalt pavement. Industry experts say that asphalt pavement paving is a systematic and refined project that requires targeted implementation of process requirements based on pavement grade, traffic load, and climate conditions, and precise control of every technical detail, in order to achieve dual protection of pavement quality and service life.
The preparation work before asphalt pavement paving construction is the foundation for ensuring smooth construction progress and preventing quality hazards. The core includes four key links: base treatment, material control, equipment debugging, and scheme preparation, each of which has clear technical requirements.
Base treatment is a prerequisite for paving construction, which directly affects the adhesion between the asphalt surface layer and the base layer, as well as the overall stability of the road surface. It is necessary to strictly follow the technical requirements of "smoothness, solidity, cleanliness, and no hidden dangers". Before construction, a comprehensive inspection of the base layer should be carried out to remove debris, floating slurry, and dust from the surface of the base layer. Defects such as cracks and depressions in the base layer should be repaired to ensure that the flatness of the base layer meets the standard specifications. The gap between 3m straightedge inspections should not exceed 5mm. For semi-rigid base layers, it is necessary to ensure that the unconfined compressive strength of cement stabilized crushed stones after 7 days meets the standard requirements. The strength of the base layer for expressways and main roads should not be less than 4.0MPa, the strength of the sub base layer should not be less than 3.0MPa, and the compaction degree should not be less than. At the same time, it is necessary to spray a prime coat oil on the surface of the base layer, using PCR modified emulsified asphalt, with a spraying amount controlled at 0.8-1.2kg/m ², ensuring a penetration depth of not less than 8mm, enhancing the adhesion between the base layer and the asphalt surface layer, and preventing interlayer peeling problems.
Material control is the core of ensuring paving quality, and the quality of asphalt mixture directly determines the wear resistance and crack resistance of the road surface. Before construction, it is necessary to strictly inspect the core materials such as asphalt binder, coarse aggregate, fine aggregate, mineral powder, etc., check the specifications, models, quality certificates, and qualification certificates to ensure compliance with design requirements and regulatory standards. The selection of asphalt binder should be based on climate conditions and traffic loads. The softening point of SBS modified asphalt should not be lower than 65 ℃, and the ductility at 5 ℃ should not be lower than 20cm. The coarse aggregate should be basalt or diabase, with a crushing value not exceeding 20% and a needle like content not exceeding 15%; Mechanical sand is preferred for fine aggregates, and the amount of natural sand should not exceed 20%. The use of natural sand is strictly prohibited in SMA mixtures. Material storage should be standardized, and asphalt should be stored in dedicated storage tanks with proper insulation measures; Aggregates should be classified and stacked, and treated with dust and moisture prevention measures to avoid mixed pollution. In addition, before construction, it is necessary to complete the design and testing of the asphalt mixture mix proportion, determine a reasonable oil stone ratio, and control the allowable deviation within ± 0.3% to ensure that the performance of the mixture meets the standard.
Equipment debugging and scheme preparation are equally indispensable. Paving construction requires specialized equipment such as pavers, rollers, asphalt mixture mixing equipment, and transportation vehicles. Before construction, all equipment must be fully debugged to ensure stable performance. The ironing board of the paver needs to be preheated in advance, with a temperature not lower than 100 ℃, and the speed of the spiral feeder needs to match the paving speed; The roller needs to check the rolling pressure and walking speed to ensure the compaction effect; The mixing equipment needs to adjust the mixing temperature and time to ensure uniform mixing of the mixture. At the same time, the construction unit needs to prepare a special paving construction plan based on the road grade, paving thickness, and traffic conditions, clarifying the paving process, technical parameters, construction flow, quality control standards, and emergency measures. After approval, it can be put into implementation. The plan needs to specify the loose paving coefficient, with AC type mixture loose paving coefficient controlled between 1.15-1.35 and SMA mixture controlled between 1.05-1.20, which needs to be verified and determined through a test section.
The mixing and transportation of asphalt mixture is an important intermediate link in paving construction, and its process specifications directly affect the paving quality. It is necessary to focus on controlling the mixing parameters and transportation details. The mixing of the mixture must strictly follow the requirements of the specifications, control the mixing temperature and time. The mixing temperature of ordinary asphalt mixture should not be lower than 150 ℃, and the mixing temperature of modified asphalt mixture should not be lower than 160 ℃. The mixing time should be controlled within 30-60 seconds to ensure that the asphalt and aggregate are fully mixed without any white material or clumping phenomenon. During the mixing process, real-time monitoring of the oil stone ratio and gradation of the mixture is required, with no less than 3 random inspections per shift to ensure compliance with design requirements.
Clean and sealed transportation vehicles should be selected during the transportation process. Before transportation, the carriages should be cleaned and coated with isolation agents to prevent the mixture from sticking to the carriages. During transportation, insulation measures should be taken, and the top of the carriage should be covered with tarpaulin to reduce temperature loss and ensure that the temperature of the mixture meets the requirements when it is transported to the paving site. The temperature of ordinary asphalt mixture should not be lower than 140 ℃, and the temperature of modified asphalt mixture should not be lower than 150 ℃. Transport vehicles should queue up in an orderly manner to avoid random parking or turning around at the paving site. When unloading, they should cooperate with the paving machine in a coordinated manner, unload at a constant speed, and prevent segregation of the mixture.
On site paving is the core process of asphalt pavement construction, and the technical points mainly include four aspects: paving temperature, paving speed, paving thickness, and paving smoothness. It is necessary to strictly follow the regulatory requirements and accurately control every detail. The paving temperature needs to be strictly controlled. During paving, the temperature of ordinary asphalt mixture should not be lower than 135 ℃, and the temperature of modified asphalt mixture should not be lower than 145 ℃. If the temperature is too high, it is easy to cause the mixture to age, while if the temperature is too low, it will affect the compaction effect and cause problems such as looseness and lack of compactness.
The paving speed should be kept uniform and stable, generally controlled at 2-3m/min, matching the production capacity of the mixing equipment and the transportation efficiency of the transport vehicles, to avoid sudden changes in speed that may result in substandard road surface smoothness. During the paving process, the paver should maintain a constant speed and not stop or turn randomly. The ironing board should be kept stable to avoid floating up and down. The paving thickness should be accurately controlled based on the design thickness and loose paving coefficient. The paving thickness of the upper layer on expressways and main roads is generally 4-5cm, and the paving thickness of the lower layer is 6-8cm. During the paving process, the thickness needs to be monitored in real time and adjusted in a timely manner. The smoothness of paving is a key indicator and requires the use of a 3D paving system to assist in construction, ensuring that the elevation error does not exceed ± 2mm and the International Roughness Index (IRI) after compaction does not exceed 2.0m/km.
Rolling forming is the key to improving road compaction and enhancing road stability. It is necessary to follow the principle of "closely following, slow rolling, high frequency, and low amplitude", and select rolling equipment and processes reasonably. Rolling is divided into three stages: initial rolling, secondary rolling, and final rolling. The initial rolling is carried out using a steel wheel roller, with a rolling speed controlled between 1.5-2km/h and two passes of rolling. The main purpose is to stabilize the mixture; Re compaction is carried out using tire rollers or steel wheel rollers, with a rolling speed controlled at 2-3km/h and 4-6 passes to ensure that the road surface compaction meets the standard. The compaction degree of the asphalt surface layer on expressways and main roads is not less than 98%; The final compaction is carried out using a steel wheel roller, with a rolling speed controlled between 2-3km/h and 2 passes of rolling. The main purpose is to eliminate rolling marks and improve the smoothness of the road surface.
During the rolling process, the rolling temperature should be controlled. The initial rolling temperature should not be lower than 130 ℃, the re rolling temperature should not be lower than 110 ℃, and the final rolling temperature should not be lower than 70 ℃. When the temperature is too low, rolling should be stopped to avoid damaging the road surface. At the same time, during compaction, it is necessary to avoid sudden braking and U-turns of the roller on the road surface to prevent problems such as road displacement and cracks. Joint treatment is a weak link in paving construction and needs to be closely controlled. Longitudinal joints are paved in a staggered manner, with a lap width controlled between 10-15cm, and the lap joints need to be compacted by rolling; Horizontal joints require the use of a cutting machine to remove loose layers, with a cutting depth of 1/3 of the layer thickness. Before paving, a layer of adhesive oil should be applied to ensure that the joints are tightly bonded without cracks or looseness.
The post construction maintenance after paving construction is an important support to ensure the quality of the road surface and extend its service life, and must strictly comply with regulatory requirements. During the maintenance period, traffic must be closed off and vehicles are prohibited from passing to avoid road damage caused by crushing. The maintenance time should be determined based on temperature conditions, generally not less than 7 days. It can be shortened appropriately in high temperature weather and extended in low temperature weather. During the maintenance period, it is necessary to regularly check the condition of the road surface and promptly clean up any debris. If cracks or looseness are found on the road surface, timely repair measures should be taken. After maintenance is completed, a comprehensive inspection of the road surface is required, with a focus on indicators such as smoothness, compaction, and water permeability. Only after passing the inspection can traffic be opened.
The reporter learned that the "Technical Specification for Construction of Highway Asphalt Pavement" (JTG F40-2004) has been implemented since January 1, 2005, further improving the technical requirements for asphalt pavement paving construction, absorbing new technological achievements such as 3D paving and modified asphalt application, and providing clear guidance for industry construction. Industry experts remind that the construction of asphalt pavement is related to traffic operation safety and engineering durability. Construction units need to strictly implement the quality responsibility system, strengthen the full process standardized control, strictly follow relevant technical specifications, optimize the construction plan based on the actual project, strengthen professional training for construction personnel, and improve the level of standardized operation. In the future, with the continuous promotion of intelligent construction equipment and new materials, the standardization and refinement level of asphalt pavement construction will be further improved, providing strong guarantees for the high-quality development of China's highway transportation and helping to create a safe, comfortable, and durable transportation environment.
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