Quality control plays a critical role in the application of prefabricated buildings. Addressing quality issues with appropriate solutions is essential to ensure successful construction outcomes.
1. Some exterior wall panels were not designed to have a 600mm upturned edge, and water stop grooves were omitted, leading to water leakage.
Prevention and Control Measures:
a. Cut and chisel off the reversed insulation board at the bottom of the upper prefabricated wall panel and the top of the lower exterior wall panel, following the width specifications from the node drawings. This creates a fire isolation zone and facilitates waterproofing work.
b. Before installing the upper prefabricated wall panels, clean the base of any debris. After internal and external grouting, install the panels, align them precisely, and secure them temporarily. Spray water into the grouting holes before grouting to ensure the grout remains fluid and compact.
c. Apply two coats of JS cement-based waterproof coating within a 200mm range above and below the horizontal joint.
d. Perform a spray test similar to that used for exterior aluminum alloy windows. If no leakage occurs, the joint is considered qualified, and external insulation can be applied.
2. Unreasonable design of embedded bolts, on-site omissions, and excessive use of expansion bolts as substitutes have caused blocked electrical conduits and increased costs.
Prevention and Control Measures:
a. The design department should provide the construction site with embedded bolt positioning diagrams based on the 3D model, including diagonal support lengths and angles. They should also verify potential collisions with conduits or junction boxes during construction and provide timely revised drawings.
b. On-site quality personnel must inspect the embedded bolts according to the positioning diagrams, checking for correct placement, secure fixing, thread length, and protection. If collisions with conduits or junction boxes are found, the project technical leader or design department should be contacted promptly to propose modifications.
3. Improper stacking of laminated boards without distinguishing specifications or compliance with regulations can lead to deformation and cracking. Additionally, supports for composite panels installed incorrectly cause cracking.
Prevention and Control Measures:
a. Stacking areas must be flat and organized according to specifications, with consistent blocks stacked evenly above and below. Stacking height should be limited to six layers.
b. Horizontal components should be lifted with a slow lift, fast lift, and slow placement method to minimize stress.
c. Temporary supports should be placed no more than 0.5m from the horizontal component supports, and intervals between supports should not exceed 2m along the length. For composite panels with spans of 4m or more, additional temporary supports are required at the midpoint to prevent sagging, with arching limited to 0.3% of the panel span.
4. Components stacked randomly on site, with wooden blocks in upper and lower rows misaligned, easily cause cracks.
Prevention and Control Measures:
a. Ensure the stacking site is level. If uneven, adjust cushion blocks so the bottom blocks align on the same plane, ensuring panels are supported evenly and flat.
b. Limit laminated board stacking to no more than 10 layers, with 6-7 layers being optimal.
c. Cushion blocks must not be missing between layers, and vertical cushion blocks should be aligned in a straight line. All blocks must comply with specification requirements.
5. Issues with prefabricated wall panel lifting deviations.
Prevention and Control Measures: Correct the wall’s position immediately. Construction teams should strengthen on-site management to prevent recurrence, while supervisory units enhance inspection and oversight.
6. Damage caused by collisions during lifting.
Prevention and Control Measures: Verify the wall’s verticality, adjust fixing bolts to maintain stability, and reconstruct dense mortar areas to ensure compactness. Construction teams must improve lifting management, standardize procedures, and avoid careless handling.
7. Missing fixing points for embedded bolts on prefabricated component slant supports.
Prevention and Control Measures:
a. Construction teams should identify and mark all fixing points according to drawings. Before pouring concrete, carefully inspect the quantity and quality of reserved reinforcement points to ensure none are missing or improperly positioned.
b. Supervisory units and the client’s engineering department must strengthen acceptance inspections of these points.
8. Insufficient grouting in prefabricated components.
Prevention and Control Measures:
a. Before hoisting, check that grouting pipes and joints are unobstructed. Lightly moisten pipes with water about 30 minutes before grouting, ensuring no water accumulation.
b. Use a pressure grouting machine to fill all holes in one continuous operation. Compact and smooth the grouting holes before the grout sets.
c. Use grouting material within 40 minutes after mixing to ensure proper setting.
9. Lack of reserved tension bars in prefabricated components.
Prevention and Control Measures:
Construction units must strengthen inspections of cast-in-place nodes. Supervisory teams and clients should conduct re-inspections. Prefabricated R&D designers should add tension bars where needed and carefully review designs for omissions. For components already produced but not installed, wall reinforcement should be planted on the side. For installed components, reinforcement should be applied at joints later.
10. Rebar deviation issues in prefabricated components.
Prevention and Control Measures:
Use steel reinforcement positioning frames based on component numbers, supported by props to ensure accurate placement. After concrete pouring, recheck the center positions of reserved reinforcing bars against layout plans and control lines. For deviations greater than 10mm, corrections should be made following the drawings.
11. Excessive sealing mortar application.
Prevention and Control Measures:
a. Reimplement blocking measures and submit the handling plan for approval by supervisors and the client’s engineering department before execution.
b. Construction units must enhance on-site management and strictly prohibit excessive mortar use that could compromise grouting quality.
Article Source: Construction Engineering Lecture Hall
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