Asphalt pavement is the most important pavement structural layer located on the pavement base. It directly bears the role of wheel loads and atmospheric natural factors. It should have comprehensive performances such as flatness, solidity, durability, and resistance to rut, cracking, slippage, and water damage. The quality of asphalt pavement construction directly affects the design service life of the highway and driving safety issues. For this reason, common common quality problems, formation causes and prevention measures for asphalt pavement are specially formulated:
1. The proportion of the nominal maximum particle size of the mixed aggregate and the pavement thickness is not matched.
2, asphalt mixture is not good.
3. The mixture is unevenly mixed and segregation occurs during transportation.
4, paver is in poor working condition and no two paver is used.
Prevention and control measures:
1. Appropriately select asphalt mixture with the nominal maximum particle size of the first-level aggregate to be suitable for the paving thickness.
2. Appropriately adjust the production mix ratio ore grading so that slightly coarse aggregates are close to the upper limit of the grading range and finer aggregates are close to the lower limit of the grading range.
3. When transporting and loading materials, the feed should be charged at least three times to avoid forming a cone to cause the coarse aggregate to roll off the bottom of the cone.
4. Adjust the paver to the best state. The opening of the material door before the screed should be consistent with the maximum particle size of the aggregate. The height of the mixture on the spiral cloth maker should be basically the same, and the material surface should be more than 2/3 higher than the spiral cloth maker.
2. asphalt surface layer compaction degree unqualified reason for the formation:
1. Poor grading of asphalt mixture.
2. The rolling temperature of the asphalt mixture is not enough.
3. The roller has a small quality and the number of compactions is insufficient.
4. The roller has not reached the edge.
5. The standard density is inaccurate.
Prevention and control measures:
1. Ensure good grading of asphalt mixture.
2. Take good insulation measures to ensure that the rolling temperature of the asphalt mixture is not lower than the prescribed requirements.
3. Choose a roller that meets the required quality to compact, and the number of compactions complies with the regulations.
4. When using embedded curb , the curb should be installed before the asphalt surface construction. The roller should be rolled from the outside to the center and rolled close to the curb; when using paved curb, the mixture on the edge can be slightly raked high with a rake, and then the outer wheel of the roller extends outward to about 10cm, and the width can also be 30~40cm at the edge. After the first press, most of the weight of the roller should be placed on the compacted mixture surface and then pressed the edge to reduce the edge to move outward.
5, strict Marshall test to ensure the accuracy of Marshall standard density.
3. Uneven compaction of asphalt surface layer
. Reasons for formation:
1. The asphalt mixture is isolated during loading and unloading and paving, and the local mixture temperature is too low.
2. The crushing is chaotic, and the roller machine set is insufficient, resulting in local pressure leakage.
3. The rolling temperature is uneven.
Prevention and control measures:
1. The material truck should move back and forth during loading, and should be covered with insulation during transportation.
2. Adjust the height of the feed of the paver so that the mixture in cloth is full and flush.
3. Organize the roller reasonably to ensure the overlap and compaction of the press wheels.
4. Reasons for the formation of dry feed
:
1. The moisture content of sand and ore materials is too high, resulting in the temperature of the coarse materials being too high when the fine materials are dried.
2. There are many pores of aggregates.
Prevention and control measures:
1, fine aggregates and ore powder should be stored, to ensure that the moisture content of fine aggregates is less than 7% before drying.
2, when the factory temperature of the mixture exceeds the regulations, it should be discarded.
3. For coarse aggregates with large pores, the heating time should be appropriately extended to cause the moisture in the pores to evaporate, but the heating temperature should be controlled.
5. The void ratio of asphalt surface layer is not qualified.
. Reasons for the formation of:
1. Marshall test porosity is too large or small.
2. The compaction degree is not controlled within the specified range.
3. The fine aggregate content in the mixture is relatively low.
4 and oil and stone control is worse than .
Prevention and control measures:
1. Take the aggregate at the hot material silo of the asphalt mixing station to ensure that the asphalt mixture ore grading complies with the regulations.
2. Ensure that the production ratio of oil and stone is within the specified error range.
3. Control the rolling temperature within the specified range.
4. Select the specified roller to control the number of rolling times.
5. Strictly control the compaction degree.
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6. The oil-stone ratio of asphalt mixture is not qualified.
. The reason for the formation of:
1. The actual mix ratio and the production mix ratio are too large.
2. The fine aggregate content in the mixture is relatively high.
3. The asphalt weighing meter of the mixing building is too large.
4. When the contractor sets the oil-stone ratio of the mixing building, the lower limit of the production ratio is used.
5. The oil and stone ratio test error is too large.
Prevention and control measures:
1. Ensure the quality uniformity of stone.
2. Check and calibrate the asphalt weighing meter on the mixing floor and obtain metrological certification.
3. Adjust the production mix ratio to ensure that the oil-stone ratio is within the specified range.
4. Carry out oil and stone ratio tests carefully according to the test procedures.
5. Ensure the normal operation of the vacuum cleaner and the accuracy of the amount of mineral asphalt.
6. Calculate the daily asphalt usage and aggregate ore usage to verify whether the oil-stone ratio meets the requirements.
7. The aggregate is crushed during asphalt surface construction
. The reason for the formation of:
1. The crushing value of limestone aggregate is relatively large.
2. There are many flake-like particles of coarse aggregate needles.
3. The soft stone content or calcite content in stone is relatively high.
4. The crushing procedure is unreasonable.
Prevention and control measures:
1. Select coarse aggregate with smaller crush value.
2. Choose coarse aggregate with small content of needle flake particles.
3. Control the number of rolling times to reach the specified compaction limit, do not overpressure.
4. The rolling should be carried out according to the initial pressure, recompression and final pressure procedures. The steel wheel should be used for initial pressure, rubber wheel should be used for recompression, and steel wheel should be used for final pressure. The rolling should follow the principle of light first and then heavy, from low to high.
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8. The powder-glue ratio in asphalt mixture inspection is not qualified
. The reason for the formation of:
1. The amount of oil used does not meet the standards.
2. The amount of ore powder does not meet the standards.
3. The crushing value of limestone aggregate is too large or the needle-shaped content is too high, resulting in the crushing of stones increasing by less than 0.075mm grading quantity.
4. The aggregate particles contain dust. When designing the production mix ratio, the aggregate was not screened by water washing method.
5. The vacuum cleaner device of the Mixed Building failed to effectively vacuum.
Prevention and control measures:
1. Strictly control the production mix ratio of asphalt mixture.
2. Choose stones with small crushing value, less content of needle flake particles and less content of particles below 0.075mm.
3. When designing the production mix ratio, the aggregate screening is subject to water washing.
4. Ensure the accuracy of the effective amount of ore powder and asphalt used in the mixing and floor vacuum cleaner.
9. The thickness of the asphalt surface layer is insufficient.
causes the formation of
1. The loose laying coefficient was not carefully determined during the trial laying.
2. During construction, the loose laying thickness was not adjusted according to the daily test results.
3. The paver or leveling device has not been adjusted.
4. The grassroots elevation exceeds the standard.
Prevention and control measures:
1. Carefully determine the loose laying coefficient during trial laying, and adjust it according to the actual testing situation during construction every day.
2. Adjust the working status of the paver and leveling device.
3. Before the construction of the lower layer, carefully check the elevation of the lower sealing layer. The part of the base layer exceeds the standard should be scraped off, the lower sealing layer should be repaired, and then the lower layer should be spread.
4. Check the paving thickness based on the total amount of asphalt mixture spread per day and make adjustments.
01. The horizontal cracks of asphalt surface layer
. Reason for the formation of:
1. The cracks of the base layer are reflected on the asphalt surface layer.
2. Dig trenches and bury pipelines at the base.
3, channel settlement joint, uneven settlement occurs in the joint of the tail of the plate and the base layer.
4. The top surface of the lower bearing layer has not been cleaned, and there is floating material or contamination. asphalt concrete produces lateral cracks during rolling.
5. During the final pressing, the temperature of the asphalt mixture is low, the asphalt bonding force decreases, and the thrust during rolling produces rolling fuses.
Prevention and control measures:
1. During the construction of the base layer, strictly control the mix ratio, compaction degree, and strengthen maintenance work, deal with the grassroots, and take anti-crack measures to reduce horizontal cracking of the base layer.
2. Strictly control the backfill quality of the roadbed of trenches, structures, and platform backs. When backfill, the steps should be dug and compacted in layers. A glass fiber mesh is laid on the cracks at the base layer, the tail of the bridge head plate and the top of the channel settlement joint to reduce the impact on the surface layer and reduce the lateral cracks in the surface layer.
3. Before paving asphalt concrete, the top surface of the lower bearing layer must be cleaned.
4. Strictly control the temperature of asphalt concrete during final pressure and roll it in time.
11. Longitudinal cracks of asphalt surface layer
causes the formation of:
1. Uneven foundation settlement causes longitudinal cracks on the roadbed.
2. Unqualified fillers (such as expansive soil) are used for roadbed filling, and the roadbed absorbs water and expands, causing road surface cracks.
Prevention and control measures:
1. Reinforce the foundation, fill the roadbed with qualified filler or process the filler before filling.
2. Cut out a certain width of the base layer on both sides of the crack, and use the measures to level the base layer with reinforced concrete with a thickness of no less than 20cm to deal with it. Add a glass fiber web to treat it, and then lay the asphalt surface layer.
causes the formation of
1. Poor soft foundation treatment causes uneven settlement of the roadbed and causes uneven settlement of the road surface.
2. After soft foundation treatment, the roadbed is filled without waiting for settlement to stabilize, causing uneven settlement of the roadbed to cause uneven settlement of the road surface.
3. The loading pre-pressure time is insufficient, resulting in uneven settlement after paving.
4. The dark pond that was not found when clearing the roadbed surface causes uneven settlement of the roadbed and causes uneven settlement of the road surface.
5. The compaction of the roadbed or pavement base and the base layer is insufficient, resulting in uneven settlement of the road surface.
Prevention and control measures:
1. Perform soft foundation treatment according to the specifications, and pavement after settlement is stabilized.
2. Control the load pre-pressure time according to design requirements and settlement rate to avoid early unloading.
3. Strictly control the rolling of roadbed filling and the compaction of road surface base and base base.
12. The residual stability of asphalt mixture is unqualified. Reasons for the formation of
1 and 4# materials are too high and the sand equivalent is unqualified.
2. The hydrophilic coefficient of ore powder is unqualified.
3. The amount of oil used is relatively low.
4. The ratio of the part less than 0.075mm to the asphalt usage exceeds the standard.
5. The test method is not standardized.
Prevention and control measures:
1. Select qualified raw materials for construction.
2. Strictly control the amount of asphalt to ensure that the oil-stone ratio meets the requirements.
3. Standardize the operation methods of oil and stone ratio detection and testing.
13. The flatness of the asphalt surface layer exceeds the standard
. The reason for the formation of
1. The paver and leveling device are not adjusted properly, resulting in uneven loose paving surfaces.
2. Stop the car and wait for materials during paving.
3. The material transport truck reverses the unloading and hits the paver.
4. The flatness of the lower bearing layer is very poor.
Prevention and control measures
1. Carefully set and adjust to keep the paver and leveling device in a good working state, and adjust it at any time according to the test paving effect.
2. During the construction process, there should be a material transport truck in front of the paver waiting for unloading to ensure that the paving is carried out continuously and evenly, and that the paving must not be stopped in the middle, and must not be fast or slow at times. The paving every day will only be stopped at work.
3. The flatness of each layer of the pavement should be strictly controlled.
14. Reasons for the formation of rut
:
1. The amount of oil used in asphalt is relatively high and the thermal stability is poor.
2. The asphalt mixture is fine in grade, and the coarse aggregate is in a suspended state.
3, channelization traffic for heavy vehicles.
Prevention and control measures:
1. Improve the grading of asphalt mixture and use more coarse aggregates.
2. Use modified asphalt to improve the high-temperature performance of asphalt.
15. Causes of the formation of kengtang
:
1. The strength of the base layer is uneven, or the strength is lost locally.
2. The local compaction or strength of asphalt concrete is insufficient.
3. Local water seeps into the asphalt concrete, causing water damage.
4. Low temperature construction, poor oil and material bonding.
5. The mix ratio of asphalt mixture is incorrect, the oil is used too little, the bonding material is heated too much, and the bonding force is lost.
Prevention and control measures:
1. Strengthen the management of grassroots construction, construct according to operating procedures, and improve the uniformity of grassroots strength.
2. Adjust the mix ratio of asphalt mixture and adjust the matching combination of the roller.
3. Avoid low-temperature construction, strictly feed the material according to the mix ratio, and control the heating temperature of asphalt and mineral materials and the discharge temperature of asphalt concrete.
16. Reasons for the formation of oily
:
1. The amount of asphalt is relatively high.
2. The amount of oil used for lower sealing or adhesive layer of asphalt is too high.
3. Use too fine materials or too much fine materials.
Prevention and control measures:
1. Strictly control the oil-stone ratio.
2. Control the amount of sealing asphalt according to the design.
3. Strictly control the asphalt concrete mix ratio.
17. slurry
. Reasons for the formation of:
1. After the asphalt concrete cracks or produces a pond, water enters the base layer to produce a suction effect.
2. The surface strength of the base layer is insufficient.
Prevention and control measures:
1, use cement to stabilize the gravel base layer.
2. Strengthen the cleaning and rinsing of the top surface of semi-rigid base layer .
18. Loss of adhesion strength
. Causes of formation:
1. The bondability of stone in asphalt mixture to asphalt is poor.
2. The stone has a high mud content and the surface of the stone is covered with mud.
3. The pores on the asphalt pavement are too large, resulting in long-term waterlogging damage.
4. Inadequate amount of asphalt.
5. Stone is crushed or the stone is highly absorbent.
6. The temperature is too high during the asphalt mixing process, resulting in aging.
Prevention and control measures:
1. Add anti-flaking agent.
2. Strictly control the mud content of stone.
3. Improve the asphalt mixture ratio, adjust the roller combination, and control the compaction degree.
4. Control the amount of asphalt according to the construction mix ratio.
5. Strictly control the mixing temperature of the asphalt mixture.
Quality control measures:
1. Before large-scale construction of the upper and lower layers, trial paving sections must be made. After on-site actual testing and demonstration, the mechanical supporting facilities, loose paving coefficient, standard compaction degree, rolling number, etc. are determined. Construction of the entire section can only be carried out after all technical indicators are passed.
2. The quality of asphalt concrete raw materials and the quality of asphalt concrete mixture should be used as the key monitoring objects in asphalt concrete paving construction:
1. The construction unit should carefully design the target mix ratio and production mix ratio according to the incoming raw materials. The supervision unit should send professional supervision engineer to control the asphalt mixing yard side stations, and strengthen the quality inspection of raw materials: mainly asphalt, coarse aggregate, fine aggregate, filler, wood floc fiber, anti-flaking agent, etc.
a. Check whether the materials entering the site have factory certificates and certificates of conformity. Bulk local materials should be inspected on site and sampled and analyzed.
b. The supply location and quantity of all materials must be approved by Supervision Engineer before entering the site.
c. Special personnel should conduct inspections and tests before entering the site. Only after passing the site can they enter the site.
d. The quality management department should conduct random inspections of materials that have entered the site at any time. Once unqualified ones are found, clear the site and return the goods immediately.
e. Check the quality of the mixture: oil-stone ratio, mineral grading, stability, flow value, void ratio; the factory temperature of the mixture, the temperature of the transport to the site, the paving temperature, the initial pressure temperature, the final rolling temperature; the mixing and mixing uniformity. The guarantee system for temperature control of asphalt mixture in each link of construction should be: asphalt and aggregate heating temperature, asphalt mixture mixing temperature, asphalt mixture exit temperature, asphalt mixture reaching site temperature, and asphalt mixture start rolling temperature. The repressing temperature of asphalt mixture and the final pressure temperature of asphalt mixture.
On-site supervision engineers must also check the number of crushings of each process.
After mixing 3 to 5 trucks of mixing materials per day, the laboratory should take samples in a timely manner, conduct timely tests, and provide feedback in a timely manner (notify the technical person in charge of the mixer of oil and stone ratio and mineral grading to make adjustments in a timely manner). Adhere to the experimental system of randomly testing oil and stone ratio and mineral grading once every day in the afternoon. Supervision engineers must strictly control them.
3. The quality monitoring station will strengthen quality inspections during the asphalt concrete paving process, mainly to guide production, test and test asphalt mixtures according to the specified items and frequency every day, check the inspection of forming pavement, such as compaction degree, flatness, thickness, elevation, deflection value, etc., and check the quality assessment of the test sections.
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