Construction of experimental section of Zazuo-Nanbai expressway pavement?

What are the specific contents of the construction of Zhazuo-Nanbai expressway pavement test section? The following Zhong Da Consulting brings you relevant introduction for your reference.

I. Overview The Zhazuo-Nanbai expressway Project is an important part of Guizhou Yuzhan National Highway (GZ50). At the same time, it is also one of the planning lines of Guizhou highway skeleton network "two vertical, two horizontal and four connecting lines". The pavement works of contract section 18 of Zazuo-Nanbai expressway Project, the starting and ending pile numbers are located in Hetaoqing Village, wujiang town, Zunyi County (YK811.366) and the ending pile numbers are located in Nanbai Town, Zunyi County (k12082/. The coarse-grained subbase test section of Zhazuo-Nanbai expressway Project is located at the right side of separated subgrade YK81.366-YK81.365, with a length of 203.634M, a pavement width of1.25m and a thickness. It was cloudy and the temperature was 17-2 1℃. By monitoring the whole process of paving, rolling, temperature measurement and coring. On the basis of obtaining and mastering a large number of experimental data, a set of relatively complete, reasonable and feasible construction experience is summarized through processing and sorting. It laid a good foundation for the construction of the whole pavement. Second, the purpose of paving the experimental section of the lower layer of coarse-grained asphalt concrete Through the experimental section of hot-mix hot-mix asphalt mixture pavement, feasible construction methods and schemes can be found in the two stages of trial mixing and trial paving to guide the construction of this section. In order to achieve this goal, we should first start from the following aspects: (1) whether the target mixture ratio is appropriate, whether the standard mixture ratio for production and the optimal asphalt content are appropriate; (2) Whether the type, quantity and combination mode of construction machinery match; (3) Whether the operation process and machine condition of the mixer are normal; (4) Whether the spraying method and effect of prime coat oil and slurry seal coat are ideal; Whether the paving and compaction process of asphalt mixture makes the determination of paving coefficient of lower layer close to reality. Three. Construction methods and technical measures 1. Asphalt concrete mixing station (Japanese model 3000) is used to mix and supply full-face hot-mixed asphalt mixture to ensure the uniform temperature of the mixture. The mixing time of asphalt mixture shall be determined by trial mixing based on the fact that the mixture is evenly mixed and all mineral particles are wrapped with asphalt binder. 2. The mixture shall be transported to the paving section by a dump truck of 15T or more. The ratio of traffic volume and mixing capacity of asphalt mixture transport vehicle to paving speed should be surplus. When transported to the site, the temperature shall not be lower than 145℃, and covering insulation measures shall be taken according to weather conditions and construction conditions. 3. Paving A. Mechanically paving hot-mix asphalt mixture is paved with asphalt concrete paver (ABG423 type), and the paver daubs a small amount of diesel oil in the hopper before receiving the material for the first time to prevent the material from sticking. Asphalt paver has: (1) semi-automatic device for adjusting paving thickness and leveling; (2) The receiving hopper with sufficient capacity can be continuously paved when the truck is replaced, and there is enough power to drive the truck; (3) Heatable vibrating screed; (4) The paving width can be adjusted. B. Paving temperature: the paving temperature of asphalt mixture shall not be lower than 135℃ in normal construction and 150℃ in low temperature construction. C loose paving coefficient: according to the actual mixture type, construction machinery and construction technology, the loose paving coefficient of asphalt mixture is selected as 1.2 through the construction method of the test section and combined with previous practical experience, which can be adjusted according to the actual situation in actual construction. D. Compaction thickness: multiply the design thickness by the loose laying coefficient 1.2 to obtain the loose laying thickness. And then roll to obtain a compacted thickness. E paving speed: asphalt mixture must be paved slowly, evenly and continuously. 4. Compaction molding A. Compaction target: the compacted asphalt mixture meets the requirements of flatness and compactness; Meet the requirements of design structure thickness and design elevation. B. Compaction technology: The compaction of asphalt mixture is divided into three stages: initial compaction, density compaction and maintenance compaction. Rolling operation adopts double steel roller, and some rolling operations adopt tire roller, which is divided into three stages and runs at a constant speed. (1) Initial pressure: Initial pressure shall be carried out when the temperature is high after paving the mixture. The light steel roller (12T) is used for slow and uniform rolling twice, and the rolling temperature is determined according to asphalt consistency, roller type, air temperature and paving layer thickness, and the mixture structure is determined through pressure test, which conforms to relevant specifications. Initial pressure can make the mixture initially stable without displacement and cracks. After initial pressure, check the flatness and road arch, and trim it properly if necessary. (2) Re-compaction: Heavy-duty tire roller (25t) will be used immediately after initial compaction, and the wheel width of the roller will overlap with adjacent compaction zones 1/3- 1/2. Roll it twice until it reaches the compaction degree required by rolling, and there are no obvious wheel tracks. (3) Final pressure: Final pressure shall be carried out after recompression. The final compaction shall be done twice by vibration compaction with BMW double steel roller (25t). Finally, the light steel wheel roller is used to eliminate the wheel tracks produced in the rolling process, so as to ensure the good smoothness of the road surface and meet the requirements of various design indexes. 5. Joints of hot-mix asphalt concrete pavement A. Joint construction requirements: Construction joints and joints at both ends of the structure must be carefully operated to ensure tightness and smoothness. B. Construction of longitudinal joints: the longitudinal joints for ladder operation are hot joints during paving. During construction, the mixture paved for the first time has a width of 10-20 cm, and the roller is mainly pressed on the newly paved pavement with a width of 10- 15 cm, and then it is gradually rolled across joints to eliminate seam marks. C. Transverse joint construction: the transverse joint is perpendicular to the road centerline, and the asphalt mixture at the end is compacted and kept within the width range of 40-50 cm, and its thickness and smoothness are checked. Then it is hardened by spraying water manually, and the streamlined end of the mixture compacted by the roller is cut off vertically. During the second construction, pave at the end, and gradually compact and compact, so that it has good cohesiveness and smoothness, so as to avoid tripping. Four. Based on the measured data and preliminary conclusions of the construction of coarse-grained asphalt concrete test section under YK8 11366-YK81365, the data and preliminary conclusions obtained from the test section are1. The construction mix ratio of coarse-grained asphalt concrete under the layer is 30% of 20-25mm gravel. 10-20mm gravel14%; 5- 10 mm gravel13%; 0-5mm stone chips 39%; 4% mineral powder; Asphalt 3.8%. The optimum asphalt content of 3.8% is obviously suitable. 2. According to the original construction experience, the proposed value of loose paving coefficient is 1.2, and the actual test result after rolling is 1. 18. 3. The construction permeability coefficient of the test section meets the design requirements. (Limited to space, it is omitted here. 4. All the quality and technical control indexes of the construction in the experimental section meet the design and specification requirements. 5. Roller combination is double steel roller (12t), rubber roller (25t) and double steel roller (BMW brand 25t). 12t double steel roller vibrates once under static pressure; Vibrate twice with 25t rubber-tyred roller, twice with 25t BMW double-wheel roller, and statically press once or twice with 12t double-wheel roller until corners and wheel tracks are eliminated. 6. Two pavers, assistant worker 12, paving speed is about 3.5m/min. After laying, it began to vibrate. 7. Stir each tank in the building for 45 seconds; The average output is 240 tons per hour. 8. The average paving length per 44 tons of asphalt mixture is 21.4m ... 9. Factory temperature 160℃, transportation temperature 155℃, paving temperature15/kloc, initial pressure temperature/kloc-0. Five, several problems that should be paid attention to in the construction 1. The length of the rolling section of the roller should keep pace with the walking speed of the paver; It should be controlled within the range of 50-80m. 2. In the process of rolling, if the mixture sticks to the roller, sprinkle a small amount of washing powder water or soybean oil on the roller by hand and smear it on the rubber roller with a mop. It is forbidden to spray diesel oil. 3. The roller shall not turn, turn around or stop on the road section that has not been cooled by rolling, and the vibrating roller shall turn off the vibration when driving on the formed road surface. 4. Local positions such as side ditches, corners, widened places and other structures that cannot be compacted by the roller shall be compacted by vibration rammer, and the edges of rainwater wells and various inspection wells shall be manually compacted by hot iron rammer and ironed by hot iron. Conclusion Through the construction of this experimental section, it is felt that the trial mixing, trial paving and rolling forming of coarse-grained asphalt concrete mixture have finally been verified by the core sample, which can be used to guide the overall construction and production. At the same time, it is also realized that as a test section, the construction section is bound to be very long, and various influencing factors are ever-changing, and various test indicators still need to be adjusted accordingly. Only in this way can we effectively ensure the quality of pavement construction and meet the actual needs of construction production. ?

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