Construction of the pavement test section of the Zazuo-Nanbai Expressway?

What specific contents are included in the construction of the pavement test section of the Zazuo-Nanbai Expressway? Below, Zhongda Consulting will bring relevant introductions for your reference.

1. Overview The Zazuo-Nanbai section expressway project is an important part of the Chongqing (Chongqing) Zhan (Zhanjiang) national highway trunk line (GZ50) in Guizhou. It is also one of the planned lines of the "two vertical, two horizontal and four-linked lines" of Guizhou's highway skeleton network. The pavement construction of the 18th Contract Section of the Zazuo-Nanbai Expressway Project starts from Hetaoqing Village, Wujiang Town, Zunyi County (YK81 161.366), and ends at Nanbai Town, Zunyi County (K120 821.800). The total length is 39.66 kilometers. The coarse-grained lower layer test section of the Zazuo-Nanbai Expressway project is located in the YK81 161.366-YK81 365 section on the right side of the separated roadbed. The length of the test section is 203.634M, the road width is 11.25M, the thickness is 8CM, and the area is 2291 sqm. The climate conditions at that time were cloudy and the temperature was 17-21°C. By monitoring the entire process of paving, rolling, temperature measurement, and drilling core sampling in the test section, we have initially obtained and mastered a large amount of test data, and after processing and sorting, we have summarized a set of relatively complete, reasonable, and practical Actionable construction experience. It laid a good foundation for the full-scale construction of the road surface. 2. The purpose of paving the coarse-grained asphalt concrete lower layer test section is to find a practical construction method and plan in the two stages of trial mixing and trial paving through the hot-mix hot-paved asphalt mixture pavement test section. to guide the construction of this section of road. To achieve this goal, we must first start from the following aspects: (1) Whether the selection of the target mix ratio is appropriate, and whether the standard mix ratio and the optimal amount of asphalt for production are appropriate; (2) The type, quantity and combination of construction machinery Whether the method matches; (3) Whether the operating process and machine condition of the mixer are normal; (4) Whether the spraying method and effect of the permeable oil and slurry seal are ideal; the paving and compaction process of the asphalt mixture leads to the following The paving coefficient of the layer determines whether it is close to reality. 3. Construction methods and technical measures 1. Use an asphalt concrete mixing station (Rigong 3000 type) to mix and supply the entire hot mix asphalt mixture to ensure uniform temperature of the mixture. The mixing time of the asphalt mixture shall be based on the fact that the mixture is evenly mixed and all mineral particles are completely coated with the asphalt binder, and shall be determined by trial mixing. 2. Transportation: The mixed materials are transported to the paving section by dump trucks of more than 15 tons. The transport volume and mixing capacity of the asphalt mixture transport truck should be more than the paving speed. The temperature when transported to the site shall not be lower than 145°C, and covering and insulation measures shall be adopted according to weather conditions and construction conditions. 3. Paving A. Mechanical paving The hot mix asphalt mixture is paved with an asphalt concrete paver (ABG423 model). Before the paver receives the material for the first time, a small amount of diesel oil is applied in the hopper to prevent sticking to the hopper. The asphalt mixture paver has: (1) A device for semi-automatic adjustment of paving thickness and leveling (2) A receiving hopper with sufficient capacity, which can pave continuously when the transport truck is changed, and has enough power to push the transport truck; (3) Heated vibrating screed; (4) The paving width can be adjusted. B. Paving temperature: The paving temperature of asphalt mixture should not be lower than 135℃ for normal construction and not lower than 150℃ for low temperature construction. C. Loose paving coefficient: The loose paving coefficient of the asphalt mixture is selected as 1.2 based on the actual mixture type, construction machinery and construction technology, through the construction method of the test section and combined with past practical experience. In actual construction, it can also be based on the actual Situation adjustment. D. Compaction thickness: Multiply the design thickness by the loose paving coefficient of 1.2 to get the loose paving thickness. After further rolling, the compacted thickness is obtained. E. Paving speed: The asphalt mixture must be spread slowly, evenly and continuously. 4. Compaction and shaping A. Compaction target: The compacted asphalt mixture meets the requirements of flatness and compaction; meets the requirements of the design structure thickness and design elevation. B. Compaction process: The compaction of asphalt mixture is carried out in three stages: preliminary compaction, density compaction and health compaction. A double steel wheel roller is used for rolling operations. The tire roller performs partial rolling operations in three stages and travels at a uniform speed. (1) Initial pressing: Initial pressing is carried out at a higher temperature after the mixture is spread. Use a light steel wheel roller (12T) to roll it evenly twice at a slow speed. The rolling temperature is based on the consistency of the asphalt, the type of roller, the temperature, the thickness of the paving layer, and the mixture structure is determined by pressure testing and complies with relevant specifications. The initial pressure can make the mixture initially stable and prevent it from shifting or cracking. After initial pressing, check the flatness and road camber, and make appropriate adjustments if necessary. (2) Re-pressing: Follow the initial pressing, using a heavy-duty tire roller (25t), with adjacent rolling belts overlapping 1/3-1/2 of the rolling wheel width. Roll it twice until it reaches the required compaction and there are no obvious wheel marks. (3) Final pressing: The final pressing is carried out immediately after the re-pressing. The final pressing uses a double steel wheel BMW roller (25t) to vibrate and roll twice. Finally, a light steel wheel roller is used to eliminate the wheel marks generated during the rolling process and ensure the road surface. Good flatness and make it meet the requirements of various design indicators. 5. Joints of hot mix asphalt concrete pavement A. Joint construction requirements: The construction joints and the connections at both ends of the structure must be carefully operated to ensure tightness and smoothness.

B. Longitudinal joint construction: The longitudinal joints using echelon operation during paving use thermal joints. During construction, leave 10-20cm of width of the previously paved mixture without rolling it temporarily. The roller should mostly press it on the road that has been paved and rolled, only 10-15cm of width should be pressed on the newly paved road, and then gradually move across the road. Press seams to eliminate seams. C. Construction of transverse joints: The transverse joints are perpendicular to the center line of the road. After the asphalt mixture at the end is rolled and compacted, a width of 40-50cm is left to check its thickness and flatness with a three-meter ruler. Then it is hardened with manual watering and the road roller is installed. After rolling, the streamlined end of the mixture is cut off vertically. During the second construction, the end is paved and gradually rolled flat and dense so that it has good adhesion and flatness and will not jump. . 4. Data obtained from the test section and preliminary conclusions Based on the actual measured data and preliminary conclusions from the construction of the test section of the lower layer of coarse-grained asphalt concrete in the YK81 161.366-YK81 365 section: 1. The construction mix ratio of the lower layer of coarse-grained asphalt concrete is: 20-25mm gravel 30%; 10-20mm gravel 14%; 5-10mm gravel 13%; 0-5mm stone chips 39%; mineral powder 4%; asphalt 3.8%. The optimal asphalt content is 3.8%, which is obviously very suitable. 2. The loose paving coefficient was determined to be 1.2 based on the original construction experience, and the test result after actual rolling was 1.18. 3. The construction water seepage coefficient of the test section meets the design requirements. (This is omitted due to space limitations) 4. All quality and technical control indicators for the construction of the test section are in compliance with the design and specification requirements. 5. The roller combination is a tandem roller (12t), a rubber tire roller (25t), and a tandem roller (BMW brand 25t). The 12t tandem roller is subjected to static pressure and vibration once; the 25t rubber tire roller is vibrated twice, the 25t twin drum BMW roller is vibrated twice, and the 12t tandem roller is statically pressed once or twice until the corners and wheels are Trace elimination. 6. There are 2 paver operators and 12 auxiliary workers. The paving speed is about 3.5 meters/minute. The vibration is turned on after paving. 7. The mixing floor stirs each pot for 45 seconds; the average output is 240 tons per hour. 8. The average paving length of every 44 tons of asphalt mixture is 21.4 meters. 9. The factory temperature is 160°C, the delivery temperature is 155°C, the paving temperature is 151°C, the initial pressing temperature is 146°C, the re-pressing temperature is 134°C, and the final pressing temperature is 82°C. 5. Several issues that should be paid attention to during construction 1. The length of the rolling section of the road roller should be synchronized with the traveling speed of the paver; it should be controlled within the range of 50-80m. 2. If the mixture sticks to the rolling wheel during the rolling process, manually sprinkle a small amount of washing powder water or soybean oil on the rolling wheel and mix it with it and apply it on the rubber wheel with a mop. Sprinkling diesel is prohibited. 3. The road roller shall not turn, turn around or park on the road section that has not been rolled, formed and cooled. The vibration of the vibratory roller should be turned off when driving on the formed road surface. 4. For local locations such as gutter joints, blind corners, and widened parts that cannot be compacted by the road roller, vibrating tamping plates are used for compaction. The edges of rainwater wells and various inspection wells are manually compacted with heated iron tamping plates. , iron it with a hot soldering iron. 6. Conclusion Through the construction of this test section, it was felt that the trial mixing, trial paving and rolling forming of the coarse-grained asphalt concrete mixture were finally verified by drilling core sampling, and the purpose of trial paving was achieved, which can be used to guide the overall construction. Production. At the same time, we also realized that as a test section, the construction section must be very long, various influencing factors are ever-changing, and various test indicators still need to be adjusted accordingly. Only in this way can the construction quality of the road be effectively guaranteed and the actual needs of construction and production be met.

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