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asphalt concrete pavement construction problems and solutions
With the rapid development of modern high-grade highways, asphalt concrete pavement has been widely promoted, and formed a pavement structure, material
materials, construction and testing as the core set of technologies, construction technology has been greatly improved, in part
asphalt concrete pavement technology and quality in general is at or near the international advanced level. However, the quality of asphalt concrete pavement by the personnel, materials, equipment, technology
process and the level of environmental and other factors, as well as the complexity of asphalt pavement construction process, system and relevance and impact of constraints
. Therefore, the necessary monitoring mechanism is very important, as the supervision of the construction units should be required in strict accordance with the approved construction design
and regulatory requirements for proper and orderly construction.
road construction in every process, every element of our overall quality of the final direct impact on the road. Therefore,
only on the various processes are to be monitored carefully in order to guarantee access to qualified asphalt concrete pavement.
one.
Asphalt concrete mixing process of asphalt concrete mixing and asphalt quality from time to time there will be instability or volatility is high, any kind of asphalt
all this green mixture, in the standardization and mechanization of the assembly line construction, are difficult to ensure the quality of asphalt concrete pavement. For example, uneven temperature or the mixture of different specifications of the original composition of mineral aggregate production variability is not large or regular testing for a variety of different specifications of mineral aggregate particles will lead to current values, changes in porosity, thus affecting road quality. So we will be taking a daily screening test and the results were analyzed longitudinal exchange, making it the basis for guiding the production and asked to adjust the proportion of cold bin; also require the construction unit must strictly control the mixing floor vibration sieve hole size. Practice shows that the control of the following sieve size is appropriate.
1 # sieve grading control the maximum size = + (1-2) mm
2 # sieve = (level with the maximum size of -5 mm control) / 2 + (1-2) mm
3 # screen = 5mm + (1-2) mm
4 # screen = 3mm
so appropriate adjustments can do, how to crown a new paragraph with the three-lane asphalt concrete choice AC25 sieve 33,16,6 , 3 shaker better.
asphalt concrete mixture in order to maintain proper quality, we test supervisors full-time course of routine testing have found that question for timely corrective treatment.
-type surface layer of asphalt penetration procedures and requirements of the construction according to the following:
one, setting out and installation of curbs.
Second, clean the grass roots.
three, poured through the layer or layers of asphalt. Thickness of 4 to 5 cm penetration pavement should be poured through the layer or layers of asphalt.
four, and threw the main floor stone shop. Paving stone the size of particle concentration should be avoided and should be checked for loose lay thickness. Vehicles should be prohibited to pass on a paved stone floor.
V. rolling. After the main floor stone paving should be 6 to 8 tons with the initial pressure roller, the speed should be 2 km / h, rolling should be gradual shift from the road edge of the road center, overlapping each wheel track is 30 cm, then from pressure the same way the other side to the road center. After rolling over the road humps should be examined and vertical slope, when there not meet the requirements should be flexible flat and then pressure, and should be rolled two times, the stone is basically stable, with no significant passage of time so far. Then 10 to 12 tons roller (the thickness of a large penetration pavement roller can be 12 to 15 tons) were rolling,
mulberry Handbags, each round of the track should overlap 1 / 2 or more, and should be rolled 4 to 6 times, until the main floor stone embedded crowded close, so far no significant wheel tracks.
coagulation on the asphalt mixture at the type of mineral aggregate maximum size can be divided into coarse-grained type (LH-30 and LH-35), the grain type (LH-20 and LH-25), fine grain type (LH-10 and LH-15), and sand type (LH-5).
asphalt mixture can be divided into coarse gravel-type (LS-30 and LS-35), in grain-type (LS-20 and LS-25) and fine type (LS-10 and LS-15).
standard asphalt concrete mixture porosity remaining after compaction, can be divided into: Ⅰ type: residual porosity of 3 to 6% in urban road 2 to 6%, the sidewalk system is 1.5 to 5% and Ⅱ: the remaining 6 to 10% porosity.
mixing asphalt mixture shall meet the following requirements:
one, according to a single feed ingredients and mixing, and strictly control all kinds of mineral aggregate and asphalt content.
Second, the control of various materials and the heating temperature of asphalt mixtures.
Third,
handbag uk, after the asphalt mixing uniform, no gray, no separation of coarse and fine material and Cluster into blocks and so on.
four samples in each class to do asphalt mixture performance, composition of aggregate gradation and asphalt content tests.
five, the end of class mixing, cleaning the mixing equipment, vent pipes in the asphalt. Make the inspection records, do not meet the technical requirements of the provisions of the asphalt mixture should be banned factory (field
II. Quality
paving paving quality directly affects the overall quality of the road, so this
our asphalt concrete pavement construction supervision in the process of focus. In addition to paving the quality of work and machinery related to the performance itself, but also depends on the paving of the continuity, stability, uniform, as well as the balance of feed and other factors,
leather handbags, so this stage also more problems, such as:
(1) non-uniform thickness of asphalt concrete pavement is always an objective reality, it will cause spread coefficients in the same song with different thickness of the compaction effect resulting in different surface roughness to influence. Therefore, in addition to improving the flatness of the grass roots and elevation control, should also strengthen the following asphalt pavement roughness and elevation of the monitoring, so that some compensation, strict control of up layer by layer, until the top layer.
in exceptional circumstances, to ensure the pavement thickness, then take the appropriate height adjustments to ensure that the thickness of pavement structure.
(2) paver and shops there will be some distance after the two-way slope, which is a great influence on pavement roughness. Repeatedly verified by arch gravity sag and screed and screed paving temperature preheat temperature difference in temperature between river size. Therefore, we require screed preheating temperature not lower than 80 ° C, with water level leveling and screed under the support plate to determine the thickness (the thickness of support plate thickness = pine + ironing board preheat shop camber + grass-roots level error, generally require a five fulcrum). Especially when the whole lot of paving, the paving should be adjusted before the arch of the same slope, and timely adjustments, in particular to stop before spreading to check, adjust, to avoid seams when the second high in the low road width .
(3) paver and paving screw feeder walking speed dial does not match the material spreader room too much or too little product, resulting mixture under screed thickness away from the pack, we ask that spiral windrow paving mixture indoor flush to or slightly above the height control screw axis line of paving. Especially the spiral phenomenon spreading device not idling.
(4) uneven paver walking speed, the speed of uneven paving, asphalt road surface waves, seriously affecting the smoothness and degree of compaction. Therefore, we request that it shall ensure that 3 ˉ 4 m / min speed of walking, try to avoid downtime. Case of a shutdown, lock screed paver should not make it sink. Pause time in temperatures above 10 ° C should not exceed 10 minutes. Pause for more than 30 minutes or mixture below 100 ° C when the cold joints in accordance with the method to re-seam. Paver to ensure that at least three cars before material to be spread, to minimize downtime and avoid the formation of waves.
(5) in the stability of walking on the paver, the following types of questions often:
a, paver track online because of the discharge and withdrawal of driving down the aggregate is not promptly removed , resulting in abrupt paving thickness. Therefore, in the construction process, construction personnel supervision and inspection at any time, in order to avoid this from happening.
b, truck reversing impact paver, pavers caused distortions forward, leaving the road surface convex blank, we ask that the process of continuous paver, paving haul trucks should be at front of stop at 10 ˉ 30cm , and neutral gear, relying on the slow push forward paver;
(6) in the construction of middle and upper classes, because leveling beam (drag bars) stiffness, and deflection is small, landing wheels and skis much, its own weight distribution is reasonable, walking stability, so we asked to use leveling beam, which is to improve road surface roughness and thickness played a very good effect.
III.
Rolling rolling technology is mainly bitumen surface forming process is to ensure the quality of its physical and mechanical properties of the road and features an important part of the design requirements, but also the last one in asphalt pavement construction process. Supervision requirements in the baking our responsibilities to the people, valet operation, found to be in place promptly corrected, and requested the construction unit to note the following:
(1) the rolling over, pushing the road cracks often occur that the stability of asphalt concrete pavement has a great influence.
Therefore, the initial pressure, final pressure of rolling temperature of timely detection, to ensure that the final pressure within the design requirements.
(2) roller surface in the new paving on the fast start and brake firmly not allowed to require skilled, experienced drivers
operation;
(3) of asphalt concrete surface water caused by excessive cooling too fast, so that the surface cracking of asphalt concrete, so the roller wheel on the water should be strictly controlled, as long as you can stick round, the impact of rollers rub the effect of asphalt concrete.
(4) checked before using the tire means the tire roller wear and pressure are equal, defense is not soft and hard on the tires
one of the lateral surface smoothness.
IV. Site sampling and testing
trial would often test out the results and the actual difference more, so we asked to do the following:
(1) asphalt samples by statistical methods to determine the set aggregate gradation of asphalt content, compaction of asphalt aggregate sampling locations in the pre-mixed with hot mix of people next to the device, asphalt content tests should be behind the paver and roller in front of the mixture from the paving samples, compaction test concrete pavement should be good to take the sample pressure to get test results, if errors or paving immediately mixing plant site, and make the appropriate measures.
(2) mixture to take a sample every kind of mix 500T, the results from our approval.
(3) When the construction unit to make tests on the various indicators, self-parallel experiments to do in order to make use of its review.
five. Seaming
asphalt pavement joints are unavoidable operating interruptions and two cases with the structures of the joints, joint position focused on the impact of surface roughness of the adverse factors, the quality is good or bad quality of road significant impact, in order to improve the quality of joints required to take the following measures:
(1) its cross section cut by cutting sewing machine to ensure the joint is a vertical cross-section.
(2) slit position must be checked by three-meter ruler, rolling the joints due to the collapse of the previous total removal of the site, to reduce the length of
removal of part of a small, paving the end of the paver Vibration rammer hammer vibration to the paving to the end remained
(3) when the roller rolling landscape rolling gradual transition from cold to hot, and repeatedly filled with fine material fact, until the ruler seized by three meters
check reach the required standard so far, to begin vertical rolling.
(4) and the joint structures like the beginning of side seams with the cold, artificial paving the terminal segment to be hung flat, fine grind materials provided
pressure side of the side, to have skilled operation, in the short time to complete, to ensure the rolling temperature.
(5) with the structures joint before the first primary joints carefully check whether the flat, rolling is compact, compaction, such as
how, from the boundary between rigid-flexible multi-baking to ensure flatness.
2. Pavement Deflection Testing of new technology
Pavement Deflection of flexible pavements is a major target strength measurements. Pavement Deflection refers to the required standard axle loads, road surface wheel gap will occur in the total vertical deformation or vertical rebound deformation. New detection methods are the following.
2.1 Deflection of laser detector method
in the determination of time. The detector fixed rear wheel cars on the road gap. Use of the car left the road during the measured point rebound, driving the original fixed on silicon photovoltaic cells on the ground, rising up the probe, so that the laser beam emitted by the laser light shines into the pool of silicon photovoltaic photocurrent. According to the size of light to calculate the surface current value of the springback deformation, that is the road Pavement Deflection. This deflectometer simple operation, high accuracy, the reading is stable, small size, light weight,
gucci bag, low cost and easy to develop, and the other to rely on the light as the detector arm length, you can shoot very far. With narrow angle laser light spot is small and bright red, 10m of the far still clearly visible, can be used for rigid pavement deflection testing.
2.2 Automatic Deflection Tester Method
section of the detector on the detection of the role of the tractor to a certain speed, the determination of deflection analyzer on the chassis front end beam and supported on the ground to remain intact, when the rear wheel gap through the probe, the deflection device through the displacement sensor, is automatically recorded. Then drag the beam is measured to two times the speed onto the next measuring point tractor. Forward cycle of continuous testing. Can be output through the computer section of Deflection results.
the determination of continuous driving cars in the determination of the case carried out. It can be on the road for high density point intensity measurements, for road construction quality control, inspection and road maintenance management.
2.3 Falling Weight Deflectometer (FWD) method
FWD is through computer-controlled hydraulic system under the falling weight equipment startup assistance, so that the quality of the hammer will free fall from a height, the impact force on the load board and spread to the road, causing pavement deflection, through the distribution of : measurement points at different distances from the sensor detects the deformation of the surface structure, the signal input into the computer record system. The measuring point by way of deflection cylinder. FWD measurements are computer automatic data collection, the progress of fast, high precision. Detection of the maximum speed of up to 80km / h, built-in FWD traction device speed can be greater than 100km / h. The method is a very good full dynamic non-destructive testing equipment.
3. Pavement Detection Technology
road pavement surface roughness can be defined as a vehicle to induce vibration of the exercise of elevation changes, it is an important pavement performance indicators. Therefore, flatness of the road construction and maintenance of detection is a very important part.
roughness test equipment section is divided into two major categories of class and reaction type. Uneven road surface type determination section case, the reaction determination of road surface roughness class level. Currently, the section type of equipment, including 3m straight edge, continuous and laser flatness measurement instrument, such as Pavement, the reaction type of equipment, including vehicle-mounted bump cumulative detector.
3.13m ruler
test light to 3m straightedge placed on the road, will be moved to the end of the drawing instruments, drawing instruments by hand into the other end. In this process because of the uneven pavement, drawing instrument measured the following round needle up and down movement with animation, while at the transmission roller wheel, driven wheel rotation, and move the tape drive, the synthesis of the two movements will be painted the needle Tape down the road on the drawing geometry, and thus obtain the surface roughness values.
3.2 Continuous flatness meter
measured by the person or vehicle pulling forward of the instrument, due to uneven pavement caused by measuring the ferry up and down swing, and promote the displacement sensor measuring rod slot in the sensor hole slide up and down. This potential according to the positive and negative sensor output to determine the size and surface roughness.
greater flexibility in the use of such detector, one can drag, but also broaching, but the test efficiency is low (detection rate of ≤ 12km / h) of the method is applicable to the determination of road surface roughness, assessed the road construction quality and use of quality, but does not apply to existing large pits, determination of serious damage to the road.
3.3 Laser Pavement Analyzer
Laser Pavement Analyzer is a equipped with laser sensors, accelerometers and gyroscopes in the determination of car, it also has advanced data acquisition and processing system. Work is to test the speed of vehicles on the road to a certain exercise, fixed in a row on the chassis to pass the test laser beam laser sensor reading of the angle is reflected back to the road test, the test car fitted with the signal from the accelerometer signal to each other poor self-test vehicle to eliminate the bumps, the output section of the road the real signal. Signal processing system will come from the laser sensor analog signals into digital signals and record them. With the car moving, pitch intervals, a data collection. Through data analysis system that can display print international roughness index flatness test results.
such analyzer is a non-contact with the road surface measuring instruments, test speed, high precision. Vertical section of the road can also, cross slope, rutting and other measurements, so the detector has a broad application prospects.
3.4 meter vehicle-mounted bump cumulative
test vehicle when measured to a certain speed on the road to exercise,
gucci handbags, uneven pavement caused by vehicle vibration, the rear axle by a mechanical sensor measures the displacement of the same car one-way between the cumulative value of the VBI, in cm / km meter . VBI greater, indicating that the worse the pavement roughness.
cumulative vehicle-mounted bump road surface roughness measured by speed, low cost, easy to operate. The test results can be assessed the quality of road construction and use of comfort.
4. asphalt pavement fault testing of new technology
road often occur in the course of a wide range of damage. Damage not only affect the pavement performance and structure of the bearing capacity of the structure will affect the pavement performance. Therefore,
chloe handbags, the asphalt pavement fault detection, for asphalt pavement maintenance is important. Currently, more advanced methods of measurement at home and abroad are: camera measurements and ground penetrating radar method.
4.1 camera measurements
camera detection technology, the basic principle is to be installed on the car in the determination of special fast or high-speed video camera at a certain speed and certain camera angles, the road specified entry Cassette various diseases, and rapid processing in the field or indoor into data of a detection technology. The method is advanced, low cost, will become the road for some time the main means of damage detection.
4.2 GPR
car equipped with ground penetrating radar on the road driving a certain speed, ground penetrating radar, electromagnetic pulse transmitter, and through the road in a short time, the pulse reflected wave received by the wireless receiver, data acquisition system records returned When asked in the pavement structure and the dielectric constant discontinuity mutation. Pavement materials each layer distinctly different dielectric constant, therefore, dielectric constant mutation Department, will meet the two structural layers of the interface. According to detect a variety of road material and the dielectric constant velocity, you can calculate the thickness of each layer pavement or given water content, damage location information.
Ground Penetrating Radar Detection
thickness of asphalt pavement, pavement void, crack, fall, air streams and other diseases. The detection rate of up to 80km / h or more, the maximum detection depth of more than 60cm. At present the road non-destructive detection, ground penetrating radar has achieved good results, but also the broader applications.
5. Conclusion
To sum up, the detection of asphalt pavement technology is evolving. From static to dynamic test development testing, from manual methods to automation by the nondestructive testing damage detection to the development of detection by the single test to integrated development. The speed of detection and faster, increasing efficiency, the results more accurate.
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