Key words: white to black; Pavement reconstruction; Resonance cement pavement crusher; construction technology
Cement concrete pavement is widely used in various countries because of its advantages and low cost in early highway construction. With the gradual growth of the service life of cement concrete pavement and the increase of traffic volume, especially the increase of overweight vehicles, a variety of diseases have appeared on cement concrete pavement, which seriously affects the driving of vehicles and restricts its traffic service capacity as a main road. It is urgent to consider adopting appropriate technology and construction scheme to completely transform the old cement concrete pavement. Pavement is an important part of highway engineering. Its construction quality directly affects the driving comfort and service life. In view of the problems such as pavement breakage and cracks in the operation process, it needs to be repaired in time. Compared with the traditional repair methods, resonance crushing technology has the advantages of simple construction operation and relatively low cost, and has a good repair effect on the pavement. In the specific construction process, the construction unit shall fully understand the construction principle and construction technology of resonance crushing, strengthen quality control measures in the construction process in strict accordance with the requirements of the construction scheme, minimize construction safety hazards and effectively improve the usability of highway engineering.
1、 Resonance breaking principle
Resonance crushing means that the resonance crushing equipment drives the working hammer head to vibrate through the vibration beam, and the hammer head contacts the road surface. The vibration frequency of hammer head is adjusted to make it close to the natural frequency of cement panel, stimulate its resonance, and then break the cement concrete panel. Generally, special sensors need to be installed on the working hammer head to effectively sense the road vibration feedback. The vibration frequency is automatically adjusted by computer to find the frequency of the hit object, and cause the resonance of the cement panel at the lower part of the hammer head, so as to quickly reduce the internal friction resistance between the particles in the concrete and achieve the effect of collapse.
2、 Resonance crushing construction technology in "white to black" pavement reconstruction
1. Pavement drainage
In order to ensure the good performance of the pavement structure, the waterproof and drainage work of the pavement structure must be done well. Therefore, it is necessary to reasonably set the longitudinal seepage ditch and transverse drainage pipe to the edge of the old cement concrete pavement slab, so as to improve the drainage performance of the overlay engineering structure and increase the service life of the pavement. In order to ensure the construction progress, the drainage system shall be set up within 2 to 4 weeks before the construction of crushed petrochemical.
2. Pavement cleaning
The pavement shall be cleaned before crushing to ensure a clean pavement. Then, the pavement shall be milled by a small milling machine and the surface asphalt shall be cleaned.
2. Construction of resonance cement pavement crushing machinery
Assign special personnel to be responsible for the operation and construction of resonance crushing machinery, and 2 to 3 people shall be reserved on site to assist. During the construction of resonance crushing, the dust shall be well controlled. For example, the construction shall be carried out by sprinkler at the construction site of resonance crushing, so as to achieve the purpose of effective dust control. During this period, the time between watering and crushing shall be reasonably arranged. Generally, the interval between the two can be controlled within half an hour.
Resonance crushing shall be constructed strictly from the road edge to the middle of the road. Since the lateral binding force does not exist in the road edge, the difficulty of crushing construction will be greatly reduced. Cutting construction can be carried out along the two lanes close to the longitudinal joint, or follow the sequence from the middle to both sides. It is required to control the width of each crushing at about 20cm, and 3.5-3.75m is the width of each lane. According to the above data calculation, one lane needs 18-12 times of resonant crushing, and there must be corresponding overlapping width between two similar crushing areas, generally 2-5cm. If the curb is stored at the edge of the outer lane, it will seriously affect the construction progress and cannot fully break the pavement. In this case, it shall be ensured that the resonance machine and the lane edge form a corresponding longitudinal included angle, such as 30 ° to 50 °, and then the breaking construction shall be carried out.
After the completion of crushing and petrochemical operation in one lane, it shall be ensured that the specific crushing construction width shall be more than the lane width, such as more than 15cm. If there is reinforced cement concrete in the broken pavement, it is necessary to cut the pavement longitudinally, properly adjust the mechanical parameters of crushing and petrochemical, and fully control the excitation force and driving speed.
4. Manual crushing and dressing
After the resonance crushing construction, the local particle size does not meet the design requirements. The pavement crushing construction shall be carried out by manual construction method in time, and the position shall be replaced and compacted. The selected material is graded crushed stone to ensure that its particle size meets the construction regulations.
5. Compaction after crushing
The pavement compaction construction shall be carried out immediately after the resonance crushing construction. The main purpose of compaction is to further crush the large particle size of the completed crushing construction, minimize the gap between fragments, improve the structural strength, and provide a flat surface for asphalt paving construction. After the pavement is broken, it shall not be disturbed to ensure that the original broken appearance will not change. The smooth wheel roller can be used for compaction construction for 2 to 3 times. If there are concave convex phenomena in some parts, it shall be leveled manually in time.
6. Spraying emulsified asphalt
Spraying emulsified asphalt prime coat can not only strengthen the connectivity between various structural layers, but also improve the bonding capacity of particles between broken concrete materials, avoid water infiltration into the lower layer and increase the waterproof capacity of loose broken layer. In terms of pavement structure, the loose layer plays a greater role. If the loose layer has small particles, it can improve the settlement of the lower broken layer and self-regulation, and has the effect of stress absorption. After spraying emulsified asphalt, the loose layer will be bonded into a whole. After rolling construction, the phenomenon of sliding layer often occurs, which must be paid attention to during construction. After compacting the pavement, the prime coat oil distribution construction can be carried out according to the actual situation of pavement compaction, especially in areas with large rainfall. Generally, special equipment can be selected for prime coat spraying construction, and the oil consumption can be controlled between 1.0 and 2.3L per square meter and 1.0 to 2.0L emulsified asphalt per square meter. It is required that the prime coat oil must be uniform and uniform in thickness to ensure that the prime coat oil infiltrates into the gravel layer at a depth of 1cm. Then, ac-70 hot asphalt seal coat shall be paved, and the spraying amount shall be controlled between 1.4 and 1.6kg per square meter.
7. Spreading stone chips
After the prime coat oil distribution construction, stone chips shall be paved in front of the compacted road. The thickness of stone chips is between 5 and 10mm and the particle size range is between 16 and 19mm. By spreading stone chips, the settlement of the lower broken layer can be effectively improved, and the reflection cracks can be eliminated. Then the pavement can be rolled again. Only by rolling for many times can the good flatness of the road surface be guaranteed. It is required that the rolling speed must be controlled between 3 and 4km per hour.
8. Paving the lower layer of Asphalt Pavement
After completing the above construction procedures, it is necessary to timely carry out various quality inspection work, and the next stage of construction can be carried out after the construction quality meets the construction design requirements. That is to do a good job in paving to avoid pollution to the broken pavement. The interval between compaction and paving shall be controlled within 48h. It is required to pave the lower layer of asphalt concrete in strict accordance with the technical code for construction of highway asphalt pavement.
3、 Precautions for resonance crushing construction in "white to black" pavement reconstruction
1. Resonance crushing construction is not suitable in areas with low terrain and large road area. The water content of subgrade clay is large. If the clay is mixed with sediment, some sections need to be excavated. Resonance crushing construction is to break the original cement concrete pavement by resonance, not crushing. Therefore, the construction compactness must be effectively controlled. The construction can be stopped after the surface is flattened and stabilized. During construction, steel wheel vibratory roller (10 tons) can be selected for construction, so as to effectively improve the modulus of broken concrete, and then water tank truck can be used for watering construction on the surface.
2. Resonance crushing construction is generally carried out in a dry environment, so as to preserve the fine particles in the concrete crushing construction, form a whole with the coarse particles, and comprehensively improve the strength of the cement pavement. At the same time, the dry environment can also prevent the weakness of soil foundation and water damage of asphalt concrete surface. In order to ensure smooth drainage, the edge drainage system can be set, that is, the transverse drainage pipe can be set within 100 to 300 meters or at a lower position, so as to drain the water in the road smoothly, and the porous plastic pipe can be laid to the ditch bottom.
The role of Highway Engineering in promoting the national economy has also been widely concerned. Resonance crushing technology is one of the important technologies in the "white to black" pavement reconstruction construction of highway engineering. Its construction technology level will directly affect the overall quality of the project. Therefore, the construction unit must pay attention to the resonance crushing construction technology. Only in this way can we promote the rapid development of traffic engineering and provide a reliable guarantee for the growth of national economy.