01. Segregation of asphalt surface

Cause

1. The ratio between the nominal maximum particle size of the mixture aggregate and the thickness of the paving surface does not match;

2. Poor gradation of asphalt mixture;

3. The mixture is not evenly mixed, and segregation occurs during loading, unloading, transportation and paving;

4. The paver is in poor working condition.

Prevention

1. Appropriately select the asphalt mixture with the nominal maximum particle size of the small primary aggregate to match the thickness of the surface layer.

2. Properly adjust the gradation of the production mix ratio, so that the slightly coarse aggregate is close to the upper limit of the gradation range, and the finer aggregate is close to the lower limit of the gradation range;

3. When transporting and loading the material, it should be loaded at least three times to avoid forming a cone and making the coarse material roll down the bottom of the cone;

4. Adjust the paver to the best state. The opening of the screed front door should be compatible with the maximum particle size of the aggregate. /3 or more;

5. A rubber baffle is added under the distributor;

6. Extended screw conveyor.

02. The degree of compaction of the asphalt pavement is unqualified

Cause

1. Poor gradation of asphalt mixture;

2. The rolling temperature of asphalt mixture is not enough;

3. The quality of the road roller is small, and the number of compaction times is not enough;

4. The roller has not reached the edge;

5. The standard density is not allowed,

6. Control the rolling temperature is too low

Prevention

1. Ensure good gradation of asphalt mixture;

2. Do a good job of heat preservation measures to ensure that the rolling temperature of asphalt mixture is not lower than the specified requirements;

3. Choose a road roller that meets the required quality for compaction, and the number of compaction times meets the regulations;

4. The curb should be installed before the construction of the asphalt surface, and the road roller should be rolled from the outside to the center, and rolled close to the curb;

5. Strictly carry out the asphalt Marshall test to ensure the accuracy of the Marshall standard density.

03. The porosity of the asphalt pavement is unqualified

Cause

1. Marshall test porosity is too large or too small;

2. The degree of compaction is not controlled within the specified range;

3. The content of fine aggregate in the mixture is low;

4. The oil-stone ratio is poorly controlled.

Prevention

1. Take the aggregate and sieve it at the hot material bin of the asphalt mixing station to ensure that the mineral material grading of the asphalt mixture meets the regulations;

2. Ensure that the production oil-stone ratio is within the specified error range;

3. Control the rolling temperature within the specified range;

4. Select the road roller that meets the requirements and control the number of rolling times;

5. Strictly control the degree of compaction.

04. The thickness of the asphalt surface layer is not enough

Cause

1. The loose paving coefficient was not carefully determined during trial paving;

2. During construction, the thickness of the loose paving was not adjusted according to the daily test results;

3. The paver or leveling device has not been debugged;

4. The elevation of the grassroots level exceeds the standard.

Prevention

1. Carefully determine the loose paving coefficient during trial paving, and adjust it according to the actual inspection situation during daily construction;

2. Adjust the working status of the paver and leveling device;

3. Carefully check the elevation of the lower sealing layer before the construction of the surface layer. Appropriate treatment measures should be taken for the part of the base layer that exceeds the standard, and the lower sealing layer should be repaired, and then the surface layer construction should be carried out;

4. Check the paving thickness according to the total amount of asphalt mixture paving every day, and adjust it in time.

05. Transverse cracks in asphalt pavement

Cause

1. Cracks in the base layer are reflected to the asphalt surface;

2. The excavation trenches at the grassroots level were not carefully backfilled and compacted to bury the pipelines;

3. Uneven settlement occurs at the junction of channel settlement joints, the tail of the board and the base layer.

Prevention

1. Treat the base layer and take anti-crack measures to reduce the transverse cracks in the base layer;

2. Lay glass fiber nets on the cracks of the base, the tail of the bridge head and the top of the channel settlement joints to reduce the impact on the surface layer and reduce the transverse cracks of the surface layer.

06. Longitudinal cracks in asphalt pavement

Cause

1. Uneven foundation settlement causes longitudinal cracking of subgrade and pavement;

2. Unqualified fillers (such as expansive soil) were used for subgrade filling, and the subgrade absorbs water and expands to cause pavement cracking;

Prevention

1. Reinforce the foundation, fill the roadbed with qualified filler or treat the filler before filling the roadbed;

2. Excavate the base of a certain width on both sides of the crack, use reinforced concrete with a thickness of not less than 20cm to level the base, add glass fiber mesh on it, and then pave the asphalt surface.

07. Asphalt surface pollution

Cause

1. Cross construction, the road surface is polluted due to the dripping of oil and materials by the transport truck;

2. Mortar pollution from other engineering constructions;

3. Sprinkle the soil on the road surface during the backfilling of the central divider or the greening project to cause road pollution;

4. Diesel leakage from various construction machinery;

5. The sidewalk is not hardened, and muddy water pollution is caused by watering

Prevention

1. Implement road traffic control, standardize the driving routes of construction vehicles, and prohibit vehicles from dripping oil and materials;

2. When constructing side slopes, roofing, and isolation fences, backfilling the central divider or carrying out greening projects, color strips should be placed on the asphalt pavement surface for isolation;

3. The watering of the central partition should be sprayed instead of flushed or watered by ditches and pits;

4. Before the construction of asphalt concrete pavement, complete the projects that will cause pollution as much as possible; 5. Harden the entrance and exit or take other measures.