Bridge deck paving
Quality risk points: Pre-pour quality problems of the bridge deck pavement layer; poor quality of the bridge deck pavement layer; quality problems of the drainage holes, etc.
- Quality problems before the bridge deck pavement layer pouring.
Manifestations and hazards
(1). Inaccurate positioning of the steel mesh and insufficient lap length.
(2). Corrosion, bending or deformation of reinforcing steel mesh
(3). Overall sinking of the steel mesh.
(4). The top surface of the beam was not cleaned and the concrete of the pavement layer contained debris.
(5). Beam top surface defects not addressed.
Prevention and control measures
(1). The design should give due consideration to the reinforcement ratio of the bridge deck pavement layer.
(2). Before the construction of the bridge deck, the top surface of the beams should be inspected, and the defects of the top surface of the beams should be dealt with in a timely manner, to clean up the loose concrete, floating slurry and oil and other debris and clean, and to remove rust on the steel mesh treatment.
(3). Install and tie the steel mesh in strict accordance with construction specifications.
(4). Control the elevation of the top surface of the reinforcing mesh; encrypt the reinforcing mesh pads or set up reinforcing brackets to ensure the position of the reinforcing mesh.
(5). Avoid construction vehicles crushing the steel mesh during construction.
- Bridge deck pavement layer pouring poor quality
Manifestations and hazards
(1). Uneven thickness and elevation or large deviations from the design.
(2). Poor flatness.
(3). Surface cracks.
(4). Poor combination of pavement layer concrete and beam top surface.
Prevention and control measures
(1). Take practical measures to predetermine elevation criteria points.
(2). Improving the concrete mix ratio, minimizing the amount of cement used on the basis of guaranteeing strength, and reasonably determining the aggregate particle size.
(3). Hand chisel the top surface of the beam to remove loose concrete, floating slurry and oil stains and other debris on the surface, before pouring, use high-pressure water gun to remove the debris on the bridge deck, and there should be no stagnant water.
(4). Concrete pouring should be continuous, avoiding high-temperature hours and windy weather; when operating the vibrating beam, assign someone to control the vibrating driving speed, shovel material and filler to ensure the pavement surface is full, dense and smooth; the frequency of vibrating should be determined according to the consistency of the concrete during the construction of the slipform, and carry out the construction of the test paving section.
(5). Timely maintenance of concrete in front of wiping, not too much water should be sprinkled at the beginning of the maintenance, immediately after the surface of the wiping surface for surface hair treatment to prevent the concrete surface peeling.
(6). Before the construction of the pavement layer, the height of the top surface of the beam should be controlled and ensure that the flatness of the concrete on the top surface of the beam meets the specification requirements.
- Water drainage hole quality problems
Manifestations and hazards
(1). The concrete around the drainage holes is not dense, falling off and breaking.
(2). The drainage holes are higher than the bridge deck or blocked by debris and cannot drain water, causing the bridge deck to become waterlogged.
(3). The location of the drainage hole is not accurate, the size does not meet the design requirements, the drainage pipe can not be installed;
(4). Insufficient extended length of drainage pipe, water erosion of the structure affects its durability.
Prevention and control measures
(1). The drainage holes should be buried in strict accordance with the specifications to ensure that the top elevation is lower than the bridge deck, which is conducive to the release of water.
(2). During concrete construction, the drainage holes should be temporarily blocked to avoid blockage caused by concrete being poured into the drainage holes.
(3). Intensification of concrete tamping around drainage holes.
(4). Reserve the length of drainage pipe in strict accordance with the design requirements.
Guardrail construction
Quality risk points: Linearity not straight after cement concrete guardrail pouring; poor quality of cement concrete guardrail pouring; waveform beam linearity not smooth; poor column verticality; waveform beam beam height does not meet design requirements. Steel frame production, concrete construction and other issues see the relevant sections.
- Concrete guardrail after pouring is not straight in line
Manifestations and hazards
The finished line of the concrete fence is not straight, affecting the visual effect.
Prevention and control measures
(1). Accurate proofing, it is appropriate to succeed in proofing once to avoid errors caused by repeated proofing.
(2). The steel template with good rigidity should be used and made in strict accordance with the design dimensions, and the corners of the template should be chamfered and rounded, and the template should be linear and smooth.
(3). Carefully molded, effectively fixed, pouring section between sections should be smooth and smooth.
- Poor quality cement concrete parapet pouring
Manifestations and hazards
(1). Poor quality appearance and whitewashing.
(2). Bottom slurry leakage.
(3). Cracks or fissures in the surface.
(4). Sand lines appear at bends in the formwork.
(5). The top of the beam is not or insufficiently chiseled.
(6). The top of the beam was not cleared of debris before the concrete was poured.
The top of the beam has not been cleared of debris.
Control and prevention measures
(1). Construction personnel should carefully vibrate, especially for the bending of the formwork.
(2). Selection of suitable raw materials, admixtures and pouring of first pieces to confirm.
(3). Set up breaks and induced joints according to design requirements, induced joints shall be cut immediately after removal of the formwork.
(4). When pouring to the top surface, assign someone to repair the surface to ensure the top surface is smooth and clean after molding.
- Waveform beam linear uneven
Manifestations and hazards
The longitudinal alignment of the corrugated beam is not straight, and there are abrupt changes or fold lines that affect the linear effect.
Prevention and control measures
(1). Accurate positioning of embedded column bases.
(2). When installing the column, the position in the base should be properly adjusted according to the longitudinal alignment to ensure that it is straight along the bridge.
(3). When installing the waveform beam, the alignment should be strictly adjusted.
- Difference in column verticality
Manifestations and hazards
Perpendicularity is not up to the requirements using the drape method.
Prevention and control measures
(1). When installing a column, ensure that the column is vertical.
(2). When pouring on the buried base, the column should be effectively fixed and checked one by one by using the dropping ball method, and should be adjusted in time if found to be unqualified.
- The height of the waveform beam beam does not meet the design requirements
Manifestations and hazards
The height of the wave beam crossbeam does not meet the design requirements.
The height of the wave beam crossbeam does not meet the requirements
Control and prevention measures
(1). Strict control of the top elevation of the columns.
(2). Waveform beams should be adjusted in time after installation.
(3). Bridge expansion joint installation
Quality risk points: Poor on-site installation quality; irregular concrete pouring process; quality problems after installation of expansion joints, etc.
On-site installation quality problems
Manifestations and hazards
(1). Due to the construction vehicle traffic affecting the quality of the installation of expansion joints, loose concrete, the main beam fracture and other phenomena.
(2). Voids in the butt welds of the main beams, resulting in fractures in the welding service.
(3). The main beam is not fully welded, and the welding strength at the welding point is low and easy to fracture.
(4). Insufficient welding of the anchor bar and the reserved tendons makes the anchor bar fall off, and the expansion joint of the main beam is unevenly stressed and easy to break.
(5). The rubber strip is not installed in place, the expansion joint does not work.
- The rubber strip is not installed in place
Control and prevention measures
(1). The owner and supervisors shall coordinate construction and shall not open to traffic until the strength of the concrete has reached the design strength.
(2). Strengthen the responsibility of welding personnel and carry out welding in strict accordance with the design drawings and specifications.
(3). Co2 gas shielded welding shall be used for the welding of the main beam to ensure a full weld.
(4). The missing expansion joint embedment reinforcement shall be dealt with promptly.
(5). The rubber strips of the expansion joints shall be installed in place according to the design requirements.
- Irregular concrete pouring process
Manifestations and hazards
(1). Not chiseled and cleaned before pouring, the old and new concrete bond is not strong, easy to crack, water seepage, resulting in corrosion of the expansion joint anchor bar and main beam, reducing the service life of the expansion joint.
(2). Failure to clear debris in the gap between the back wall and beam end or on the combination pier before pouring, resulting in limited expansion joint expansion.
(3). The concrete is not dense, there are voids, resulting in the expansion joint local concrete strength is insufficient, easy seepage, accelerate the anchor bar corrosion and concrete carbonization, reduce the service life of the expansion joint.
(4). There are debris such as foam in the concrete, which causes the concrete to crack.
Prevention and control measures
(1). Strengthen construction management and strictly control the quality of the concrete mix.
(2). Before concrete is poured, debris should be removed from the reserved slot, the gap between the back wall and the beam end, and the joint pier, and the joint surface should be chiseled.
(3). Install the formwork in place and take effective measures to seal the gap between the formwork and the beam end.
(4). Strengthen the management of the pouring process, ensure that the concrete is vibrated and compacted and timely moisturized maintenance.
(5). Both sides of the expansion joint can use steel fiber concrete and other materials with high bending and tensile strength, impact resistance and fatigue resistance.
- Post-installation quality problems of the expansion joint
Manifestations and hazards
(1). The height difference with the road exceeds the specification requirements, which is prone to jumping when driving and affects the driving comfort; it causes the impact on the expansion joint and affects the service life of the expansion joint.
(2). Cracks in the concrete and water seepage can easily lead to corrosion of the anchor bar and the main beam, reducing the service life of the expansion joint.
(3). Poor flatness of concrete, easy to crack after the impact of jumping the car;
(4). The concrete is locally loose and easily damaged under the impact load of the vehicle.
(5). Breakage of the expansion joints, which affects their normal use.
(6). The expansion joint gap does not meet the design requirements, which hinders the normal performance of the expansion function
Prevention and control measures
(1). Install the expansion joint in strict accordance with the design requirements to ensure that the height difference between the expansion joint and the road surface is within the allowable range of the specifications.
(2). Compacting and timely maintenance of concrete.
(3). The concrete surface shall be smoothed and polished to ensure that the flatness meets the specifications.
(4). No traffic shall be opened until the strength of the concrete has reached the design requirements.
(5). The gap should be adjusted according to the ambient temperature when the expansion joint is installed.
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