The integral layer of bridge deck has the functions of protecting beams, leveling the bridge deck, improving the mechanical properties of the bridge deck and enhancing the integrity of the bridge deck. The advantages of full-width pouring construction technology of long-span light truss leveler can be summarized as follows: First, it reduces cross-contamination in construction and improves construction efficiency. Second, optimize the construction technology and reduce the position treatment of construction joints. Thirdly, the suspension leveler is efficient and stable, ensuring flatness and good integrity. Full-width pouring construction technology improves the construction quality of the whole layer, ensures the bridge deck quality and driving comfort, and will have a broader development prospect. Therefore, it is of great significance to analyze and apply the full-width pouring construction technology of bridge deck integral layer to optimize the construction technology of bridge deck integral layer.
1 project overview
The first bid section of the civil engineering from Jiangmen to Luoding expressway is the starting and ending bid section from Jiangmen to Luoding expressway, starting from Fokai expressway, with three interchange areas, namely Pinglian Interchange, * * * * Interchange and Meng Gu Interchange, with 265 bridges and 438+0 bridges. The length of the whole deck layer is1875m, and the width of single casting is within the range of10.5 ~15.5m.. The traditional integral layer construction technology is limited by the working width of the three-roll or two-roll pulp-lifting straightener, and generally needs to be divided into 1~2 sections for pouring construction. In this process, it is necessary to move the machine many times and dismantle the walking track, which leads to low construction efficiency, difficult treatment of construction joints and serious cross-pollution. The width of the long-span light truss vibration grader purchased in the early stage of this bid can reach18m, so the whole bridge deck layer of this bid adopts full-width pouring construction technology.
Brief introduction of two long-span light truss straighteners
The long-span light truss leveler used in the full-width pouring construction of the whole bridge deck in this bid section is GQCY series highway bridge deck vibration pulp lifting leveler. The two ends of the machine use rails for mobile paving construction, which can form multiple slopes at one time, and has comprehensive functions such as rotating vibration excitation, paving leveling and slurry lifting. The machine consists of the following parts: 1. Truss and walking system. The light truss structure used in the straightener has the characteristics of large span, light weight and easy operation. Anti-skid devices are arranged on both sides of the walking wheels at both ends of the truss, and the lifting of the truss is combined with lifting locking, which is safe and reliable. Second, paving and high-frequency excitation system. The system consists of two vibrating pulp lifting rods and accessories. The motor drives the pulp lifting roller shaft to rotate rapidly, and the vibration between the roller shaft and the truss is attenuated by the vibration damping device, thus eliminating the influence of the vibration generated by the roller shaft on the truss and ensuring the leveling effect.
3 Full-width construction technology of bridge deck integral layer
The whole layer of the bridge deck is poured with the full width of the long-span light truss leveler, and the full width is within the range of 1 0.5 ~15.5m, and each pouring is1. The following introduces the main technology of full-width pouring construction of bridge deck integral layer in this bid section.
3. 1 Preparation before construction
(1) Before the construction of the comprehensive layer, report to the survey supervision engineer to conduct a general survey of the top elevation of the beam slab, with no less than 3 beams per span and no less than 3 points per beam. If the thickness of individual points of the integration layer is less than 7cm, local treatment should be carried out. If the multi-point thickness is less than 7cm, it should be reported to the design to adjust the slope. (2) The setting of two walking tracks of the long-span light truss leveler shall ensure that the technical requirements such as flatness, elevation, longitudinal slope and transverse slope meet the design and specification requirements. (3) After thoroughly gouging out the laitance on the top surface of beam and slab including hinge joints, clean up the sundries on the bridge deck with high-pressure water gun and air compressor.
3.2 Reinforcement installation
(1) Adjust the specifications of embedded steel bars on the beam surface and check the number of embedded steel bars. If it is less than the design, reinforcement must be planted, and the depth of reinforcement should not be less than 25cm. (2) Set elevation control points on the top surface of the comprehensive layer, and the spacing is generally not more than 5m*5m. Set short steel bars on the control points and fix them on the embedded shear bars to accurately measure the elevation of the control points. (3) After the reinforcement of the whole layer is bound, in order to ensure the firmness and stability of the reinforcement, the thickness of the protective layer and the best stress position, φ 16 reinforcement head is used for support and spot welding, and the supporting point arrangement is not less than1*1m.. And some embedded shear bars are properly welded with the steel mesh to ensure the stability of the steel mesh.
3.3 Concrete construction
(1) Arrange the concrete construction time according to the weather forecast, avoid rainy days, high temperature and windy weather, and provide reliable rainproof measures, materials and equipment during construction to avoid the influence of abnormal weather on the construction quality during pouring. (2) The materials shall be discharged in strict accordance with the approved mixture ratio, and the observation of slump changes during concrete discharging, arrival at the site and paving shall be strengthened, and timely treatment and adjustment shall be made. Pumping must be adopted in concrete construction to ensure the continuity of concrete construction.
(3) According to the transverse and longitudinal slopes of each bonding layer, concrete paving and vibrating construction should be carried out from low to high. After the concrete is pumped to the designated position on the bridge deck, it will be patched evenly by manpower. Considering the settlement of concrete after vibrating, artificial paving should be slightly higher than the deck elevation. After the artificial paving is uniform, use an internal vibrator to drag the vibration, and the vibrating time is controlled at about 30s/m2. Then start the leveler to vibrate until concrete bubbles overflow.
3.4 Pulping and napping
(1) It is equipped with a long-span rigid pulp collecting bridge for pulp collecting and roughening operation, so as to avoid damage such as footprints left by constructors when working directly at the integration level. (2) When the concrete is about to set initially, it shall be subjected to secondary sizing and napping. When napping, you must first hang the thread along the transverse direction of the bridge, and then nap it to ensure that the wool line is straight. The napping depth is generally controlled at 2 ~ 3 mm
3.5 Health and wellness
After roughening, in order to prevent the moisture on the concrete surface from volatilizing before the final setting and producing early plastic shrinkage cracks, it is necessary to spray curing agent, and then cover all exposed surfaces with permeable geotextile. After the geotextile is covered, spray it with a sprayer in time. Direct washing or watering is strictly prohibited to avoid scouring the concrete surface. Immediately after the final set of concrete, the geotextile shall be kept moist with water, and the curing time shall be no less than 7 days.
4 Comprehensive layer construction quality control measures
The construction quality of the integral layer of bridge deck directly affects the quality and performance of bridge deck. Therefore, in order to ensure the construction quality of the integral layer of the bridge deck, the following control measures are taken during the construction of this bid section: (1) The processing and installation of the reinforcement of the integral layer shall be carried out in strict accordance with the design requirements of the drawings to ensure that the diameter, length, spacing, position and protective layer of the reinforcement mesh meet the requirements. (2) For the preparation of concrete mixture, the laboratory shall communicate with the mixing station in time. After strictly measuring the moisture content of materials, adjust the construction mixture ratio according to the moisture content. (3) Concrete mixing must be accurate and uniform, and it is not allowed to segregate and stay too long during transportation. When paving, strictly control the elevation and vertical and horizontal flatness of the combined layer, and cross-nap the rigid slurry collection bridge with a hard plastic brush or a capillary brush before the final set of concrete.
(4) Paving operation should be based on the transverse and longitudinal slopes of the bridge deck, starting from the lowest expansion joint of each joint and moving forward with full width. Strictly control the cement concrete not to drip into the reserved notch of the expansion joint. Single seam paving layered operation should be continuous construction, without stopping in the middle. When it is necessary to stop under special circumstances, the construction joints should be horizontal. Before the next paving, the construction joints shall be treated according to the specification requirements. (5) During the movement of the long-span light truss leveler, attention should be paid to cleaning up the sundries on the track in time to ensure the stability of the leveler. (6) If it rains before the final setting of the combined layer concrete, it should be covered with plastic sheets to prevent the rain from directly washing the concrete surface. (7) The maintenance of the integrated layer should be watered according to the regulations after the final set, and the watering frequency every day should be determined according to the weather conditions to keep the water surface moist. Before the compressive strength of concrete is lower than 7.5Mpa, it shall not bear the load of pedestrians or other objects, and before it is lower than 70% of the design strength, it shall not pass through various vehicles.
Example analysis of full-width pouring construction technology
Through the analysis of the integral pavement of the bridge deck of the No.1 civil engineering project from Jiangmen to Luoding expressway, the full-width pouring construction technology improves the qualified rate of all quality indexes of the integral pavement and reduces the labor cost. The specific analysis is as follows: (1) flatness control: five places are randomly selected from the integrated layer every 20 linear meters for flatness detection, and the flatness of the integrated layer is basically controlled within 5mm, with a qualified rate of 92%. (2) Crack control: Compared with the traditional three-wheel roller or two-wheel roller, the full-width pouring construction needs to set up multiple tracks, which can reduce the construction joints left by the tracks on the bridge deck. In addition, the long-span rigid slurry collection bridge is used for secondary slurry collection and roughening, which can also reduce the footprints left by concrete surface construction and avoid concrete cracks.
(3) Control of protective layer thickness: 3 reinforced protective layers are inspected by core-pulling of each joint, and the qualified rate is 100%. (4) Cleanliness control: people, vehicles, machinery and equipment, etc. It is easy to pollute the bridge deck in the process of traditional framing pouring construction, and the pollution caused by slurry leakage from side formwork needs a lot of manpower and material resources to clean up. The full-width pouring construction can effectively avoid the secondary pollution problem and ensure the cleanliness of the integrated layer construction. The qualified rate of each index of the comprehensive layer is improved, and the efficiency and labor force are saved in the construction, which has certain popularization and use value.
6 conclusion
The engineering example of full-width pouring of the whole bridge deck shows that the construction quality index of this technology is greatly improved compared with the traditional technology, and it has the advantages of high construction efficiency, simple equipment operation, high quality controllability and good cleanliness, which meets people's high requirements for bridge deck quality and driving comfort, and has good economic benefits and great popularization and application value.
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