With the rapid development of modern high-grade highway, asphalt concrete pavement has been widely promoted, and pavement structure and materials have been formed.

Materials, construction and testing as the core of the complete set of technologies, the level of construction technology has been greatly improved, and some asphalt concrete pavement technologies

And the overall quality and quality have reached or approached the international advanced level. However, the quality of asphalt concrete pavement is affected by personnel, materials, equipment and technology.

Technology, level, environment and other factors, as well as the complexity, systematicness and relevance of asphalt pavement construction process.

And influence. Therefore, the necessary supervision mechanism is very important. As a supervisor, the construction unit should be required to strictly abide by it.

The approved construction organization design and specifications require correct and orderly construction.

Every process and link of pavement construction directly affects the final overall quality of pavement. So,

Only by carefully supervising each process can we ensure that qualified asphalt concrete pavement can be obtained.

1. Asphalt concrete mixing

In the process of mixing asphalt concrete, the quality of asphalt mixture is sometimes unstable or fluctuating, and any of these will be lost.

It is difficult to ensure the quality of asphalt concrete pavement in standardized and mechanized assembly line construction. For example, the uneven temperature of the mixture or the variability of the composition of raw minerals with different specifications or the failure to regularly check the particle composition of minerals with different specifications in the production process will lead to the change of flow value and porosity, thus affecting the quality of pavement. Therefore, we will carry out daily sampling and screening tests, and analyze the results vertically to make them the basis for guiding production, and require timely adjustment of the proportion of cold storage; It is also required that the construction unit must strictly control the size of the vibrating screen in the mixing building. Practice has proved that it is appropriate to control the screen hole according to the following dimensions.

1# sieve = maximum particle size for classification control +( 1-2) mm.

2# sieve = (maximum particle size for classification control-5 mm)/2+(1-2) mm.

3# sieve = 5 mm +( 1-2) mm.

4# sieve = 3mm

Appropriate adjustments can be made accordingly. How to choose the vibrating screen with the mesh size of 33,16,6,3 for AC25 asphalt concrete in the new section of the third-line crown?

In order to maintain the quality of asphalt concrete mixture, our full-time test supervisor conducts daily inspection in the production process and corrects problems in time.

Asphalt permeable pavement shall be constructed according to the following procedures and requirements:

A, curb lofting and installation.

Second, clean up the grassroots.

Three, pouring through layer or adhesive layer asphalt. The permeable pavement with a thickness of 4 ~ 5 cm should be poured with permeable asphalt or viscous asphalt.

Fourth, lay the main layer of stone. When paving stones, the concentration of large and small particles should be avoided, and the loose paving thickness should be checked. It is forbidden for vehicles to pass on the paved stone layer.

5. Scroll. After paving the main layer of stone, use a 6-8 ton roller for initial compaction at a speed of 2 km/h, and gradually compact from the edge of the road to the center of the road, with each wheel track overlapping by 30 cm, and then press it to the center of the road from the other side in the same way. After rolling again, check the road arch and longitudinal slope. If there is any non-conformity, it should be leveled and flattened again, and rolled twice to make the stone basically stable without obvious displacement. Then roll it with 10 ~ 12 ton roller (thick-penetration road surface can be used with 12 ~ 15 ton roller), and the wheel track overlap should be greater than12 each time, and roll it for 4 ~ 6 times until the main stone is embedded tightly and there is no obvious wheel track.

According to the maximum particle size of mineral aggregate, the types of asphalt mixture can be divided into coarse-grained (LH-30 and LH-35), medium-grained (LH-20 and LH-25), fine-grained (LH- 10 and LH- 15) and sand-grained (LH-5).

Asphalt macadam mixture is divided into coarse particles (LS-30 and LS-35), medium particles (LS-20 and LS-25) and fine particles (LS- 10 and LS- 15).

The residual porosity of asphalt concrete mixture after standard compaction can also be divided into: Class I: residual porosity 3-6%, urban road 2-6%, sidewalk system 1.5-5%, and Class II: residual porosity 6- 10%.

The mixing of asphalt mixture shall meet the following requirements:

A, according to the ingredients list feeding and mixing, strictly control the dosage of all kinds of mineral aggregate and asphalt.

Second, control the heating temperature of various materials and asphalt mixture.

Thirdly, the asphalt mixture after mixing is uniform, without ash, separation of coarse and fine materials and caking.

Four, each class sampling asphalt mixture performance, mineral aggregate gradation composition and asphalt content test.

5. At the end of each shift, clean the mixing equipment and drain the asphalt in the pipeline. Make inspection records, and the asphalt mixture that does not meet the specified technical requirements is prohibited from leaving the factory (field).

2. Paving quality

The quality of pavement paving directly affects the overall quality of pavement, so it becomes our supervision over asphalt concrete.

Key points of pavement construction. The quality of paving operation is not only related to the performance of machinery itself, but also depends on the continuity, stability, uniform speed and feed balance of paving, so there are many problems at this stage, such as:

(1) The uneven thickness of asphalt concrete pavement always exists objectively. Under the same loose paving coefficient, the compaction effect of different thicknesses will be different, thus affecting the smoothness of the pavement. Therefore, in addition to improving the control of the smoothness and elevation of the base, we should also strengthen the supervision of the smoothness and elevation of the lower asphalt pavement to make it compensated and strictly control it step by step until the upper level.

Under special circumstances, in order to ensure the thickness of pavement, adjust the elevation appropriately to ensure the thickness of pavement structure layer.

(2) After paving, a two-way slope will appear at a certain distance, which has a great influence on the smoothness of the pavement. Through repeated verification, the camber is related to the weight sag of screed and the temperature difference between the preheating temperature of screed and the paving temperature. Therefore, we require that when preheating the leveling layer, the temperature shall not be lower than 80℃, and it shall be leveled with a spirit level, and the thickness of the pallet under the leveling layer shall be determined (pallet thickness = loose laying thickness+leveling layer preheating camber+base elevation error, generally requiring five fulcrums). Especially when paving the whole picture, the camber should be adjusted to the same slope before paving, and it should be adjusted in time, especially before paving stops, so as to avoid the high and low road width at the secondary joint.

(3) The walking speed of the spiral distributor of the paver does not match with that of the paver, which leads to too much or too little material accumulated in the paving room, thus causing the mixture under the screed to be too thick. We require the height of the mixture pile in the spiral paving room to be equal to or slightly higher than the axis of the spiral paving machine. In particular, the spiral paver will not idle.

(4) The uneven walking speed of paver makes the paving speed uneven, and waves are formed on the surface of asphalt pavement, which seriously affects the flatness and compactness. So we ask it to walk at a speed of 3 ˉ 4m/min and try to avoid stopping. When stopping the machine, the paver screed should be locked to prevent sinking. When the temperature is higher than 10 C, the suspension time should not exceed10 minutes. When the suspension time exceeds 30 minutes or the mixture is lower than100 C, the joint must be re-joined according to the cold joint method. Before the paver, at least three materials should be laid, which can minimize downtime and avoid waves.

(5) Regarding the walking stability of pavers, the following problems often occur:

A, paver crawler line due to the discharge and removal from the aggregate is not timely, resulting in a sudden change in paving thickness. Therefore, in the process of construction, urge the construction personnel to patrol at any time to avoid this situation.

B, when the truck is reversing, it impacts the paver, causing the paver to twist forward, resulting in convex edges on the road surface. We require that in the process of continuous paver, the truck should be parked in front of the paver 10ˉ30cm, put in neutral, and slowly advance by the paver;

(6) In the construction of middle and upper floors, the leveling beam (tie rod) has large rigidity, small deflection, more wheels and sledges, reasonable weight distribution and good walking stability. Therefore, we require the use of leveling beam, which plays a very good role in improving the smoothness and thickness of pavement.

Three. Rolling technology

Rolling is the main process of asphalt pavement forming, an important link to ensure pavement quality and make its physical and mechanical properties and functional characteristics meet the design requirements, and also the last process of asphalt pavement construction. In this case, our supervisor requires that the responsibility should be carried out by people and shift workers, and any deficiencies found should be corrected in time. At the same time, the construction unit is required to pay attention to the following points:

After (1) rolling, nappe cracks often appear on the pavement, which has a great influence on the stability of asphalt concrete pavement.

Therefore, the rolling temperature of initial pressure and final pressure should be detected in time to ensure that the final pressure is within the design requirements.

(2) The roller shall not start and brake quickly on the newly paved road, and it needs skilled and experienced drivers.

Operation;

(3) Too much water spray leads to too fast cooling of asphalt concrete surface, which leads to cracking of asphalt concrete surface. Therefore, the water spraying on the roller wheel should be strictly controlled, as long as it does not stick to the wheel, which will affect the rolling effect of the roller on asphalt concrete.

(4) Before using the tire roller, check whether the wear and pressure of each tire are equal to prevent the tire from being hard or soft.

First, it affects the lateral smoothness of the surface layer.

Four. Sampling and testing

In the field test, there are often many differences between the test results and the actual results, so we need to pay attention to the following points:

(1) The asphalt mixture shall be sampled by statistical method to determine the asphalt content of aggregate gradation. Before asphalt mixing, the sampling position of compacted aggregate should be close to the hot mixing equipment. The asphalt content test shall be carried out after the paver and before the roller, and samples shall be taken from the paved mixture. After the compaction test is completed, if there are any errors, it shall immediately notify the mixing building or the paving site and take corresponding measures.

(2) The mixture shall be sampled once every 500 tons, and the result shall be audited by us.

(3) When the construction unit carries out tests on various indicators, parallel tests shall be conducted for recheck.

Verbs (abbreviation of verb) are treated together.

There are two kinds of asphalt pavement joints: inevitable operation interruption and joints with structures. The unfavorable factors affecting the smoothness of pavement are concentrated in the joints, and their quality has a great influence on the quality of pavement. In order to improve the quality requirements of joints, the following measures must be taken:

(1) Cut the cross section with a seam cutter to ensure that the joint cross section is a vertical plane.

(2) The kerf position must be checked with a three-meter ruler, and all the joint parts collapsed due to the previous rolling shall be removed to reduce it.

The length of the cut-off part should be less, and the vibration rammer of the paver should keep vibrating until the end of paving.

(3) When rolling, the transverse rolling of the roller will gradually change from cold to hot, and the fine materials will be filled repeatedly until it is checked with a three-meter ruler.

The longitudinal rolling can only be started after the inspection reaches the specified standard.

(4) The beginning of the joint with the structure seems to be the same as the cold joint, and the terminal section needs to be laid manually, the line should be hung flat, and the fine materials should be filled and polished.

When pressing, it should be operated by skilled workers and completed in a short time to ensure the rolling temperature.

(5) Before joining with the structure, carefully check whether the base of the joint is smooth, whether the rolling is dense and the hardening degree is as follows.

Why, ensure the smoothness of rigid-flexible boundary from multiple surfaces.

2. New technology of pavement deflection detection.

Pavement deflection detection is the main index of flexible pavement strength measurement in China. Pavement deflection refers to the total vertical deformation or vertical rebound deformation produced by the wheel clearance position on the pavement under the specified standard axle load. There are several new detection methods.

2. 1 laser deflection tester method

At the time of confirmation. Fix the tester in the rear wheel gap of the car on the road. Using the rebound of the road when the car leaves the measured point, the probe of the silicon photovoltaic cell originally fixed on the ground is driven to rise upwards, so that the laser beam emitted by the laser is incident on the silicon photovoltaic cell through the incident light, and a photocurrent is generated. According to the magnitude of photocurrent, the rebound deformation value of pavement is calculated, that is, the rebound deflection value of pavement. The deflectometer has the advantages of simple operation, high precision, stable reading, small volume, light weight, low cost and easy development. In addition, because it relies on light as the arm length, it can shoot very far. In addition, the laser emission angle is narrow, the light spot is small and bright red, and it can still be clearly seen at the distance of 10m, so it can be used for deflection detection of rigid pavement.

2.2 Automatic deflection tester method

The tester runs at a certain speed under the action of the tractor on the measured section. The deflection measuring beam of the tester is placed at the front end of the vehicle chassis and supported on the ground to keep still. When the double clearance of the rear axle passes through the probe, the displacement sensor and other devices automatically record the deflection. At this time, the measuring beam is dragged to the next measuring point at twice the speed of the tractor. Measure forward continuously in one cycle. The statistical results of pavement deflection detection can be output by computer.

The whole measurement is carried out under the condition of continuous driving of the measuring vehicle. It can measure the strength of high-density points on pavement, and is suitable for quality control, acceptance and maintenance management of pavement construction.

2.3 falling weight deflectometer (FWD)

FWD starts the drop hammer assembly through the computer-controlled hydraulic system, so that a heavy hammer with a certain mass can fall freely from a certain height, and the impact force acts on the bearing plate and is transmitted to the road surface, resulting in the deflection of the road surface. Sensors distributed at different distances from the measuring point detect the deformation of the surface of the structural layer, and the recording system inputs the signal into the computer. Obtain the road and measure the deflection cylinder. FWD measurement is automatic data acquisition by computer, with fast progress and high accuracy. The highest detection speed can reach 80km/h, and the traction speed of the built-in falling weight deflectometer can be greater than100 km/h/h. This method is an ideal dynamic nondestructive testing equipment.

3. Pavement smoothness detection technology

Pavement smoothness can be defined as the change of pavement elevation that causes vehicle vibration, and it is an important index of pavement performance. Therefore, flatness detection is a very important link in pavement construction and maintenance.

Flatness testing equipment can be divided into two categories: section type and reaction type. The roughness of the pavement is determined by the grade of the road section, and the roughness of the pavement is determined by the reaction grade. At present, the road equipment includes 3m straightedge, continuous flatness meter and laser pavement flatness meter, and the reaction equipment includes vehicle-mounted bump accumulator.

3. 13m ruler

When testing, put the 3m ruler on the road surface gently, move the plotter to one end, and push the plotter to the other end by hand. In this process, due to the unevenness of the road surface, the animation needle of the wheel measuring belt under the plotter moves up and down, and at the same time, the force transmission wheel drives the roller to rotate, which drives the paper tape to move. The combination of the two actions makes the drawing needle draw the geometric quantity of the road surface on the paper tape, from which the smoothness value of the road surface can be obtained.

This method is used to measure the smoothness of each layer of compacted pavement, so as to evaluate the construction quality and service quality of pavement. But this method is relatively backward, the measurement efficiency is low, and the operator needs to bow his head, so it has been used less now.

3.2 Continuous flatness meter

When measuring, people or Xiangqian Che pull the instrument, and the measuring wheel swings up and down because of the uneven road surface, driving the measuring rod of the displacement sensor to slide up and down in the small hole groove of the sensor. In this way, the smoothness of the road surface can be determined according to the positive and negative potentials output by the sensor and their sizes.

This kind of measuring instrument is flexible and can be towed or pulled by car, but its detection efficiency is low (detection speed ≤ 12km/h). This method is suitable for measuring pavement smoothness and evaluating pavement construction quality and service quality, but it is not suitable for measuring pavement with many pits and grooves and serious damage.

3.3 Laser Pavement Smoothness Tester

Laser pavement evenness tester is a measuring vehicle equipped with laser sensor, accelerometer and gyroscope, and it also has advanced data acquisition and processing system. The job is to test the car running on the road at a certain speed. A row of laser sensors fixed on the chassis of the car tests the road by testing the angle of the laser beam reflected back to the reader. This distance signal is different from the accelerometer signal installed on the test vehicle, which eliminates the bump of the test vehicle itself and outputs the real road section signal. The signal processing system converts the analog signal from the laser sensor into a digital signal and records it. When the car is running, data are collected at regular intervals. Through the data analysis system, the flatness detection results such as international flatness index can be displayed and printed.

This measuring instrument is a high-speed and high-precision non-contact measuring instrument. At the same time, it can also measure the longitudinal section, transverse slope and rut of pavement, and has broad application prospects.

3.4 Vehicle-mounted buffer accumulator

In the process of measurement, the test vehicle runs on the road at a certain speed, and the unevenness of the road surface will cause the vibration of the vehicle. The cumulative value of one-way displacement between the rear axle and the bracket can be measured by mechanical sensor in cm/km. The greater the VBI, the worse the pavement smoothness.

Vehicle-mounted bump totalizer has the advantages of high speed, low price and simple operation. The test results can be used to evaluate the quality of pavement construction and the comfort of service life.

4. New technology of asphalt pavement damage detection.

Various damages often occur in the course of pavement use. Damage not only affects the structural performance and bearing capacity of pavement, but also affects the service performance of pavement. Therefore, asphalt pavement damage detection is of great significance for asphalt pavement maintenance. At present, the more advanced measurement methods at home and abroad are: camera measurement and ground penetrating radar.

4. 1 camera measurement method

The basic principle of camera detection technology is a kind of detection technology, which is a special fast or high-speed camera installed on the measuring vehicle, records all kinds of diseases specified on the road surface into the camera belt at a certain speed and camera angle, and then quickly processes them into data on site or indoors. This method is advanced and low cost, and will become the main means of pavement damage detection in the future.

4.2 Ground Penetrating Radar

When a vehicle equipped with ground penetrating radar runs at a certain speed on the road, the ground penetrating radar emits electromagnetic pulse, which penetrates the road in a short time, and the pulse reflection wave is received by the wireless receiver. The data acquisition system records the echo time and the abrupt change of discontinuous dielectric constant in the pavement structure. The dielectric constant of each structural layer of pavement is obviously different, and the sudden change of dielectric constant is just the interface between the two structural layers. According to the measured dielectric constant and wave velocity of various pavement materials, the thickness of each structural layer of pavement can be calculated or the data such as water content and damage position can be given.

Ground penetrating radar detects asphalt pavement thickness, pavement gap, cracks, subsidence, air flow and other diseases. Its detection speed can reach more than 80 km/h, and the maximum detection depth is more than 60 cm. At present, ground penetrating radar has achieved good results in highway nondestructive testing and has a broader application prospect.

5. Concluding remarks

To sum up, various technologies of asphalt pavement detection are constantly developing. From static testing to dynamic testing, from manual testing to automatic testing, from destructive testing to nondestructive testing, from single testing to integrated testing. The detection speed is faster and faster, the efficiency is higher and higher, and the results are more and more accurate.