The 4 most important points of concrete bridge deck construction
First, bridge deck pavement construction process
Single bridge deck width 12.75m, bridge deck pavement width 11.75m, thickness 8cm, bridge deck cross slope 2%, bridge deck pavement leveling layer construction process is as follows.
Second, bridge deck paving construction machinery
Third, bridge deck paving construction
3.1 Bridge deck chiseling, cleaning
(1) Poured in-situ wet joints, crossbeams and negative moment tension slot concrete using hand-push chisel machine, chisel off the concrete surface floating slurry, until the exposure of coarse aggregate, to ensure a tight connection with the bridge deck pavement concrete construction.
(2) The box girder top surface of loose concrete, soil, debris and oil pollution removal, and then blow clean with high-pressure air pump, and wash with a water gun to ensure that the bridge deck is clean and tidy.
3.2 measurement and proofing
Bridge deck pavement construction before the elevation of the bridge deck to remeasure, remeasure every 5 meters of a section, each section measuring 5 points, to determine the plane control point, and in the top of the main girders for sample, pop-up ink bucket line. Calculate the thickness of the bridge deck pavement layer by measuring the elevation of the control point.
3.3 Standard Strip Construction
Bridge deck standard with the bridge deck pavement layer elevation and construction quality control is an important step, the standard with close to the inner and outer guardrail, the width of 105cm, hanging line construction to ensure that the longitudinal line smooth, no mutation, not into a folded line, the standard with surface flatness from strict control.
(1) Standard strip sampling.
Construction in accordance with the spacing of 5m to put out height control points, measured at the control points of the bridge deck design elevation and the difference between the actual top beam elevation; control points in the standard with the implantation of the inner side of the steel, in the two bars on the horizontal welding elevation bars, positioning bars every 4m to set one, and then accurately measure the elevation with elevation, pulling line to determine the location of reinforcing steel mesh, control in the reinforcing steel mesh protection layer for 2cm, using the bridge deck door ribs fixed reinforcing steel mesh, mesh installation needs to be deep guardrail parts.
(2) Standard strip steel mesh laying.
①Standard steel reinforcement mesh in the belt for the A-type, longitudinal bridge to lay, the use of welded form for fixing, according to the standard belt design top elevation, and the actual elevation of the top of the beam piece to adjust, 2m a point to determine the distance between the steel reinforcement mesh from the top of the beam, and mark the guardrail reinforcement. Near the guardrail side, weld the ribbed steel mesh to the guardrail reinforcement, away from the guardrail side, weld the steel mesh to the erector bar, and strictly control the net protective layer of the reinforcement mesh within the standard belt.
② control the lap length of adjacent steel mesh to 20 cm, welded connections, ensure that adjacent steel mesh welded 2 meshes.
(3) The length of exposed steel mesh on the outside of the standard belt is controlled to be 25cm, ensuring that the lap length of A-type mesh and B-type mesh is 20cm, and the concrete joints avoid the steel lap position by 25cm.
(3) Standard with side mold installation.
A pair of Φ12 steel bars is implanted every 2-3 meters outside the standard strip, and the positioning bar is fixed by the burial method of drilling with electric drill (the diameter of drill bit is 10mm), the depth of drilling should not be more than 3cm to prevent damage to the roof steel of the box girder, the positioning bar is buried at a depth of 3cm, and the transverse bar is welded on it as the bottom support of the square steel of the side mould. The top of the transverse bar is placed on top of the angle steel as the side mold of the standard strip, the top of the square steel is slightly higher than the design elevation of the marked strip, and the angle steel is firmly welded with the implanted support steel to enhance its stability.
(4) Pouring of the standard strip.
Concrete pouring is pumped by pump truck, and the top surface of the box girder at the standard strip site is fully wetted before pouring concrete. Concrete is poured from low to high, concrete is vibrated by inserted vibrator (vibration placed horizontally), and artificial trowel is used to control the elevation of the steel with two adjacent elevations.
(5) Standard Strip Maintenance.
After the completion of concrete vibrating and finishing, lay down plastic film and geotextile to cover the maintenance, arrange special person for watering maintenance, and ensure the wet condition within 7 days maintenance period.
(6) Standard belt leveling and smoothing.
Adopt secondary leveling trowel construction process, can effectively control the level of the elevation belt, for the elevation belt overflow of concrete clean up with electric pickaxe, use the top surface of the elevation belt is not smooth with angle grinder grinding smooth.
(7) Notes for standard belt construction.
① Bridge deck drainage hole burial: according to the box girder girders reserved drainage holes, when pouring the standard belt set 215mm diameter PVC pipe for the bridge deck drainage hole burial.
② standard inspection with the warehouse before inspection: reinforcement mesh installed and welded firmly, the installation of embedded parts and side mold installation is complete and fixed, then self-test, self-test qualified report to the supervising engineer acceptance, ready for the standard with concrete pouring.
3.4 Reinforcing mesh positioning
Bridge deck standard with construction completed, in the laying of the remaining part of the steel mesh, the standard with the outer side of the blocking debris to be cleaned up, and the combination of parts of the chisel processing, to ensure that the bridge deck pavement twice poured effective combination.
Reinforcement mesh type: welded steel reinforcement mesh using CRB550 steel, 26m wide bridge deck using A type, B type two mesh, A type mesh laid at the bottom of the anti-collision railing position, B type mesh laid in the middle of the bridge deck.
Schematic diagram of Type A steel mesh
Schematic diagram of type B reinforcing mesh
Reinforcement mesh laying is carried out after the construction of the standard strip is completed, and before construction, the standard strip is chiseled and worked, and the elevation is reviewed, and only after passing the inspection. In the process of laying, check the arrangement of the vertical and horizontal bars in the reinforcement mesh to ensure that the reinforcement mesh is laid in the transverse direction and the longitudinal direction. After the completion of the precise positioning of the reinforcement mesh, the use of manual pull line, according to the standard control height with the direction of the bridge, the whole section of the two-person pull line for the reinforcement mesh protective layer check, found that the reinforcement mesh protective layer deviation of ± 5mm position, immediately adjusted to strictly control the reinforcement mesh in the design elevation, and to meet the requirements of the reinforcement mesh flatness ± 10mm (3m straightedge detection), for local requirements do not meet. The design is adjusted in time to meet the design requirements.
Precautions for steel mesh laying construction.
① The laying and positioning of the reinforcement mesh, the use of concrete pads for construction is strictly prohibited.
② the reinforcement mesh and erection rib welded firmly, local deformation and sinking due to reinforcement mesh for local support areas to strengthen.
③ reinforcement mesh installation, the two pieces of mesh need to lap a mesh, lap the height of the bridge deck portal bar need to be adjusted accordingly. The lap width is not less than 20cm, and the lap part is connected by single-sided welding with a weld length of not less than 10cm.
④ At the discontinuous end, the lap steel should be reserved for the installation of the steel mesh.
3.5 Concrete paving and tamping
In order to ensure that the bridge deck pavement layer pouring thickness, in the bridge deck pavement before construction, the need for joint inspection and acceptance of the bridge deck elevation, can not meet the bridge deck pavement layer thickness, local chisel processing, as far as possible to ensure that the bridge deck pavement layer thickness error control (+10, -5mm) within.
Pavement concrete pouring arrangements as far as possible at night, windless construction, construction temperature is appropriate at 10 ℃ or above, the wind reaches 6 and above must stop construction; concrete to ensure that the mixing time of not less than 120 s, using pumped concrete, pouring process to reduce concentrated discharge, to avoid damage to the steel mesh, pouring before full sprinkling of water to moisten the top surface of the box girder, to avoid the old and new concrete joint surface should appear weak layer.
The speed of concrete paving and three-roller shaft vibrating should be controlled appropriately to prevent the lower part of the concrete from being vibrated too fast, and in the process, shovels should be used to fill in the gaps near the track, and the concrete near the track should first be vibrated by tamping and supplemented by inserted vibrators (placed horizontally for vibration), and then paved with three-roller shaft.
3.6 Concrete Plastering
Before the concrete first set, the secondary finish should be carried out, which can greatly avoid the shrinkage cracks on the concrete surface. The driving power trowel is used for secondary finishing, and manual auxiliary scraping and troweling is used in some parts.
It is forbidden to sprinkle water to change the water-cement ratio of the surface concrete in the course of troweling, and when it is difficult to finish the section, it is advisable to trowel with the original slurry.
3.7 Concrete regeneration
Strengthen the initial moisturizing and thermal insulation cover maintenance. When the concrete surface can be covered with geotextile, remove the film and replace it with geotextile to cover, and evenly water the geotextile. Arrange for sprinkling maintenance work, 12:00 ~ 16:00 every 0.5 hours during the interval of sprinkling, the rest of the time every hour sprinkling, so that all the surface of the concrete to keep evenly moist, full of water curing time should not be less than 7d. 12:00 ~ 16:00, the concrete surface should always keep wet state. After curing to the end of the elevation, smoothness, cross slope, etc. for testing.
Fourth, bridge deck pavement construction quality assurance measures
(1) Assign testers to test the moisture content of the aggregate at any time to ensure that the quality of concrete mix meets the requirements of the concrete ratio and the measurement is accurate. (2) The water consumption of concrete should be controlled more accurately, and the influence of temperature on the slump of concrete should be investigated so that the concrete proportion can be adjusted in time and accurately to ensure the water retention, fluidity and ease of concrete construction.
(2) control the quality of raw materials into the field. Due to the large area and small thickness of the bridge deck pavement, considering the local thickness may be less than 8cm, the coarse aggregate particle size should be controlled within 25mm.
(3) Control the mixing time of the concrete, not less than 120s. too short or too long will affect the concrete properties, increasing the construction difficulty, and ultimately affect the smoothness of the bridge deck.
(4) The unevenness of the track on both sides of the three-roller axle directly affects the levelness of the pavement layer, the installation must adjust the top rail height, so that the joints are smooth and stable, consistent with the slope of the bridge deck, and the original bolt reinforcement distance shortened by 1/3.
(5) Arrangement of surface finish and smearing process: at the time of initial concrete setting, ride on power trowel is used for smearing and manual smearing is assisted. The leveling construction of the three-roller paving should be completed within 1/3 of the initial concrete setting time.
(6) During the construction process, the thickness of pouring should be accurately positioned, the positioning spacing should not be more than 5m, and the concrete protection layer at the bottom of the reinforcement mesh erection bar should be evenly set and the density should be sufficient.
(7) Precautions for three-roller shaft levelling machine operation.
① According to the operation unit segmental leveling, the length of the operation unit should be 30m, and the time interval between the two processes of tamping machine and three-roller shaft leveling should not exceed 15min.
Within the length of one operating unit, the three-roller shaft leveler uses forward vibration and backward rolling operation, which should be carried out 2-3 times respectively. After the completion of rolling, lift the vibrating roller from the template, use the leveling shaft static rolling and leveling before and after, until the flatness meets the requirements, the surface mortar thickness uniform until.
When working, there should be a person to deal with the material level in front of the shaft. If the material level is too high, it should be supplemented with manual eradication; if there is a gap under the shaft, it should be filled with concrete.
The thickness of surface mortar should be controlled at (4±1)mm, and the overly thick and thin mortar on the surface in front of the three-roller shaft leveler should be scraped off and discarded.
(8) Adhere to the test system during the construction process, test the concrete slump at the concrete construction site and record it in the construction records. Ensure that the frequency of concrete tests and the number of specimen groups meet the specified requirements. General concrete pouring in non-rainy days, all concrete in accordance with the specifications for all kinds of tests, and meet the construction frequency.