Asphalt pavement is the general name of pavement with asphalt as binder, which has the advantages of high strength, smooth driving, no dust, no vibration and low noise, and is suitable for roads with various traffic flows. According to the requirements of modern traffic, asphalt concrete pavement must have sufficient strength, stability (including dry stability, water stability and temperature stability), smoothness, skid resistance and as low as possible dust emission. This paper discusses the quality control measures of asphalt concrete pavement construction.
A, asphalt concrete pavement quality requirements
(1) The asphalt pavement shall have sufficient pavement resistance.
The pavement should have enough bearing capacity to balance the pavement damage caused by excessive stress in the pavement structure layer under repeated vehicle loads.
(b) Asphalt pavement should have good fatigue resistance.
During the design service life, asphalt pavement will bear the repeated action of a large number of traffic loads. In order not to cause fatigue damage prematurely, it must have good anti-fatigue characteristics.
(3) Asphalt concrete pavement should have good high temperature stability.
Asphalt mixture is a typical rheological material, whose strength and stiffness modulus decrease with the increase of temperature. Therefore, under the repeated action of heavy traffic, asphalt concrete pavement gradually forms "ruts" on wheel tracks due to channelization of traffic, which is a common problem of high-grade asphalt pavement. The high temperature stability of asphalt pavement refers to the ability of asphalt mixture to resist repeated compression deformation and lateral flow of vehicles.
(d) Asphalt concrete pavement should have good low-temperature crack resistance.
The temperature shrinkage crack of asphalt pavement is characterized by the tensile failure of asphalt film between asphalt mixture aggregates in cold season, which leads to the opening of aggregates and the formation of cracks Therefore, the low-temperature crack resistance of asphalt mixture mainly depends on the low-temperature tensile deformation performance of asphalt binder, and then has a certain relationship with the temperature shrinkage coefficient, tensile strength and stiffness modulus of asphalt mixture.
(5) Asphalt concrete pavement should have good skid resistance.
The anti-skid performance of asphalt pavement directly affects driving safety. In order to ensure the skid resistance, special attention should be paid to the wear resistance of coarse aggregate, and hard angular aggregate should be selected. The amount of asphalt and the wax content of asphalt also have obvious effects on the anti-skid performance.
Second, the control of asphalt concrete pavement construction preparation stage
The main work in the preparation stage of asphalt concrete pavement construction includes: establishing construction organization, familiarizing with design documents, rationally deploying construction personnel, designing asphalt concrete mixture ratio, setting up mixing station, preparing materials, configuring construction machinery and pavement base.
(A) the formation of the construction organization
Establishing a lean and efficient construction organization is the key to construction quality control. This requires institutional members to have a strong sense of professionalism, understand technology and management, and establish a post responsibility system at all levels, and the responsibility lies with people.
(two) familiar with the design documents, understand the design intent.
Familiarity with design documents and mastery of construction design drawings are the primary tasks of preparation before construction. Generally, the technical director of the project department will organize the blue prints.the design, and fully understand the design intent through detailed analysis and research, so as to grasp the project scale and the actual quantities of each division and sub-project, and lay the foundation for the reasonable preparation of construction organization design and construction scheme. At the same time, it can also put forward suggestions on the problems existing in the design drawings, so as to create conditions for better controlling the construction quality.
(3) Configuration of construction personnel
The quality of personnel is one of the factors that affect the construction quality, so it is very necessary to allocate more construction personnel with strong sense of responsibility and high technology in key processes.
(4) Mix proportion design of asphalt concrete
Asphalt concrete mix design is divided into three stages: target mix design, production mix design and production mix verification. This work is done by the field laboratory. This work should be carried out as soon as possible. With the mixture ratio, the specifications and quantity of materials can be accurately determined. In the production process, when the incoming materials change, the gradation of asphalt mixture and Marshall test technical indicators do not meet the requirements, the mixture ratio should be adjusted in time.
(5) Setting of mixing station
Asphalt concrete must be mixed in asphalt mixing station with mixer. The setting of mixing station needs to fully consider the transportation economy of the site location, and the site should be wide and flat, in line with the relevant national regulations on environmental protection and fire safety, and should have good rain-proof and drainage facilities; Transportation roads should be smooth, convenient and unobstructed. At the same time, flammable items such as oil and asphalt should be separated from power supply and various heating settings, and there should also be reliable power supply.
(6) Preparation of materials
Asphalt concrete materials mainly include: asphalt, stone (gravel, sand) and filler. Material quality is an important factor affecting the quality of asphalt concrete pavement, and unqualified materials can never be used in road construction. Therefore, it is very important to purchase all kinds of materials needed for asphalt concrete pavement. Shop around, choose materials with high quality and low price, and give consideration to quality control and investment control. In addition, the material supply plan shall be worked out in stages and batches. All kinds of raw materials, finished products and semi-finished products must be selected and inspected before entering the site, and materials whose indicators meet the requirements shall be selected, and unqualified materials shall not be used. Asphalt is the most important material and should be ordered directly from the manufacturer. The general design documents of asphalt label have clear requirements.
(7) Configuration of construction machinery
The selection of construction machinery and equipment should not only consider the technical performance, work efficiency, work quality, reliability and maintenance difficulty, energy consumption, safety and flexibility of construction machinery, but also consider its quantity configuration. Important machinery and equipment should have spare equipment. Generally, the asphalt concrete mixture of urban main roads and expressways should be mixed by intermittent mixer, which has an automatic batching system, which can automatically determine the mixing parameters such as mixing amount, mixing temperature and time. The smoothness of the pavement mainly depends on the paver. Urban main roads and expressways should be jointly paved with two or more pavers. The production efficiency of paver should be high, with automatic leveling and thickness adjustment devices and preliminary tamping and ironing devices. Roller adopts double steel wheel vibratory roller and tire roller for joint operation, and the quantity is determined according to the actual workload. Other mechanical equipment should match the whole construction process.
(eight) the grassroots strength is sufficient.
Asphalt concrete pavement should be paved on the base with sufficient strength, firmness and stability, and the surface of the base should not be loose and elastic. The strength, smoothness and deflection of the base have a vital influence on the paving quality of asphalt concrete pavement. Spray a certain amount of prime coat oil on the surface of the base, and the surface before asphalt paving should be free of dust and sundries, and cleaned up.
Third, the quality control in the construction stage
(1) mixing asphalt mixture
1, mixing temperature. When mixing, the temperature of asphalt is about 160℃~ 170℃. As the normal temperature mineral powder and mineral aggregate are added at the same time, in order to ensure the mixing temperature of mineral aggregate, the feed temperature of mineral aggregate is controlled at 175℃~ 190℃, and the ex-factory temperature of machine-made asphalt mixture is 155℃~ 65438. The factory temperature of modified asphalt mixture is higher. 2, the mixture shall not use recycled dust, dust must be discharged. The mineral powder used to produce asphalt concrete must be stored in the stone powder tank of the mixer and kept dry and free flowing.
3. The site laboratory samples the mixture performance, aggregate gradation and asphalt content twice a day, and the performance index of the mixture must be consistent with the tested qualified products.
4, the mixture should be uniform, no gray, caking or serious separation of coarse and fine materials, it is forbidden to unqualified products.
5. In rainy and humid climate conditions, aggregates (especially stone chips) needed for the production of asphalt mixture should be stacked in dry places. When the demand for fine aggregate is small, and it is difficult to feed the cold silo due to rain, humidity and other reasons, try not to arrange construction.
(2) Asphalt mixture transportation
As far as possible, large-tonnage dump trucks shall be used for mixture transportation, and the number of vehicles shall be reasonably allocated according to production capacity, vehicle speed and transportation distance, and an appropriate number of spare vehicles shall be reserved. During transportation, we should pay attention to the following points:
1, in order to ensure the paving temperature and prevent pollution and rain caused by leakage, all asphalt mixture transport vehicles should be covered with engine oil.
2. Before loading the truck, the trunk must be cleaned, and the bottom plate and peripheral wall of the trunk should be coated with a thin layer of oil-water mixture (diesel: water is less than 1).
3. When the mixer is unloaded from the truck, it should move the truck position of each barrel of mixture to reduce segregation.
4. The buckle of the tailgate of the dump truck body must be kept clean and easy to clip open, so as to prevent the vehicle from leaking materials during transportation, resulting in material waste and road pollution.
5. When reversing and discharging, avoid the car hitting the paver, assign a special person to command the vehicle and stop in front of the paver 10cm~30cm. In the process of discharging, a gap should be hung and propelled by paver.
6. The temperature of asphalt mixture transported to the site shall not be lower than 130℃~ 150℃. The mixture caked or wet by rain shall not be paved.
7, transport vehicles on the way back, hopper to fall, in order to avoid accidents and residual material leakage pollution road.
8. The remaining mixture in the hopper will be transported away from the paving site and away at the designated place. The garbage generated by the construction on the same day will be transported out of the construction site on the same day.
(3) Asphalt mixture paving
1, the whole picture is paved by the paver during the construction period. Paver echelon operation is adopted in the widening section, and the longitudinal joints are left in the front of the paving mixture, with the width of 10cm~20cm, which will not be rolled for the time being. As the elevation benchmark of paving behind, the paving layer overlaps about 5cm~ 10cm, and finally, the joints are rolled across in the form of hot joints to eliminate seam marks. The upper and lower longitudinal joints should be staggered by more than 15cm.
2. In order to ensure the smoothness and thickness of asphalt concrete pavement meet the design requirements, the upper layer is paved by sled to control the thickness and smoothness of the paving layer, and the paver is equipped with a mobile automatic leveling reference device.
3, in order to reduce construction joints, should ensure that each layer paving at least 65438+/-0.5 km every day.
4. In the process of paving, the paver should advance at a uniform speed according to the paving speed, vibration and vibration frequency determined by trial paving, and it is forbidden to change speed or stop halfway.
5, every day before paving, screed must be preheated, preheating temperature shall not be lower than 70℃.
6. In the process of mechanical paving, manual trimming is not allowed. Under special circumstances, manual local repair, replacement of mixture or manual paving can be adopted.
7, paving asphalt mixture before compaction, construction personnel shall not trample.
8, paving in case of rain, should immediately stop construction, and remove the uncompacted mixture after the rain.
Concluding remarks
The factors affecting the construction quality of asphalt concrete pavement include personnel, machinery, materials, methods and environment. The key is the rational allocation of personnel, materials and equipment. In the process of construction, we should be good at summing up, overcome human factors, select high-quality construction teams, and pay attention to introducing new technologies, new materials, new processes and new equipment. Strictly follow the construction plan, rectify the problems found in the construction in time, establish a post responsibility system, and make everyone responsible. As long as we strengthen the awareness of engineering quality, strengthen management and formulate scientific management methods, we can create first-class projects.
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