What are the common problems and issues in engineering quality management?

Quality is the eternal theme of engineering construction. The quality of construction projects is a major issue related to the vital interests of the people. In the mild case, it will cause rework and economic waste, affect the normal use functions of the construction project, in the serious case, it will endanger people's lives and property safety, causing serious social impact. How to strengthen quality management during the construction process is an issue that the responsible parties of all parties involved in the project should carefully consider. This article briefly analyzes some common problems and precautions in engineering construction for your reference.

1. Construction of concrete structure projects

(1) Construction raw materials

1. All construction raw materials entering the site should have product factory certificates (but the project (Manufacturer product certificates are not provided for common materials such as sand and stone); after the site entry is accepted by the supervision engineer (project leader of the construction unit), a site entry ledger will be established.

2. The mud content and stone powder content of sand and gravel used in concrete should be strictly controlled. Use natural sand as much as possible, and gravel should be of continuous particle size to avoid single particle size. Good gradation reduces the amount of cement required.

3. Cement should be retested according to the actual batches entering the site as much as possible. The ordinary Portland cement used must not be used if it has been more than three months old after leaving the factory.

4. The use of inferior steel bars is strictly prohibited. Anti-rust measures should be taken for the finished steel bars to prevent corrosion caused by the shedding of the oxide film.

(2) Steel bar installation

1. Construction should be carried out strictly in accordance with the drawings. The types, grades, and specifications of steel bars cannot be changed or replaced at will. It is prohibited to use HRB335 instead of HPB235 steel bars.

2. Pay attention to the setting of steel bars in key parts such as frame beam-column joint stirrups, primary and secondary beam encrypted stirrups, large-section beam structural distribution bars, and upper steel bars on cantilever plates such as trenches and awnings.

3. It is necessary to strictly control the effective height of the upper steel bars of the separated reinforcement cast-in-place slab; prevent it from sinking; if ready-mixed pumped concrete is used, unfavorable factors such as temperature shrinkage and deformation should be considered, and the unfavorable height of the upper steel bars of the cast-in-place slab should be considered. Temperature shrinkage bars are arranged on the surface of the reinforcement to prevent cracking of the cast-in-place slab.

(3) Formwork Engineering

1. Pay attention to the consistency between the on-site formwork erection and the special plan for formwork construction. It is prohibited to use steel pipe fastener supports instead of wooden supports at will.

2. Formwork with a floor height of more than 4.5 meters requires the use of steel pipe fastener supports.

3. If the wooden support method is used, the vertical poles shall not use multi-section overlapping method, but shall adopt the butt joint method.

4. A formwork plan with a height exceeding 8 meters, or a span exceeding 18 meters, with a total construction load greater than 10 kN/m2, or a concentrated line load greater than 15 kN/m2, shall be approved. It can be implemented only after passing the expert argumentation review.

5. The formwork should be removed based on the test report of the remaining concrete cured specimens under the same condition or the component rebound strength record. It cannot be demolished based on construction experience.

6. The post-cast belt formwork should be independent of the adjacent structural formwork. There should be construction technical plans for formwork removal and supporting roofs.

(4) Concrete construction

1. A concrete construction proportioning sign should be hung in the concrete mixing area to facilitate workers' operation.

2. The concrete mix proportion used for the first time should be evaluated at the beginning and the designed mix strength should be tested.

3. Before daily concrete mixing, the construction mix ratio should be adjusted according to the moisture content of sand and stone.

4. It is strictly prohibited to use a forklift as a measuring tool. It is not recommended to use a trolley for direct volume measurement and proportioning. Proportioning by volume can easily lead to concrete quality problems.

5. The concrete pouring time cannot exceed its own initial setting time. During the hot weather season, construction cold joints often occur in cast-in-situ concrete structures due to unreasonable construction process arrangements.

6. After the concrete pouring is completed, the surface should be plastered with no less than two coats, and should be covered, insulated and cured within 12 hours. The curing time of concrete with ordinary Portland cement shall not be less than 7 days, and the curing time of concrete mixed with retarding or impermeable admixtures shall not be less than 14 days. Improper concrete maintenance and water loss can easily lead to low surface strength and accelerated carbonization.

7. The number of test pieces used to check the concrete strength of structural components should be retained according to the regulations in the construction organization design. The standard concrete test pieces should be placed in the on-site standard curing room for curing and must not be transported out of the construction site. After the specimens are cured under the same conditions, they are removed from the formwork and installed in a customized steel cage. After being locked, they are placed close to the corresponding structural components and maintained using the same measures.

8. If there are appearance quality defects after the cast-in-place structure is removed from the formwork, the construction unit shall propose a construction technical plan and obtain approval from the supervision (construction) unit before the defects can be dealt with. The treated parts should be re-accepted and corresponding records should be made.

9. After the construction of the main bottom column of the project is completed, settlement observation points should be set up in time according to the design requirements.

10. Before acceptance of the main structure, the expansion joints should be cleaned to facilitate the discovery of quality defects and structural deformations.

2. Foundation Engineering Construction

1. For cast-in-place piles with single piles and single columns, a set of specimens must be left for each pile. If pumped concrete is used for pouring, a set of standard maintenance test specimens can be left for every 50 cubic meters. The strength of this set of test specimens represents the concrete strength of this batch of hole piles.

2. Pile foundations should be inspected for pile body quality and bearing capacity. The inspection methods and quantities should be specified by the design unit.

3. Basements with independent foundations or slab foundations should pay attention to the floating problem of the basement in time. During the construction process of this type of basement, water should be stored in the basement in time, and the backfill soil outside the wall should be backfilled in time. The backfill soil should be made of clay with poor water permeability, etc., and should be compacted in layers.

3. Construction of masonry projects

1. Before masonry construction, fired bricks and shale bricks should be watered and moistened 1 to 2 days in advance.

2. It is strictly prohibited to use stone powder as fine aggregate in masonry mortar.

3. When new wall materials such as autoclaved sand aerated blocks are used, they should be constructed in accordance with the relevant standard atlas. Mixing of different blocks is strictly prohibited. When concrete blocks are used as exterior walls, crack-resistant measures should be taken carefully.

4. The infill wall should be built to the bottom of the beam plate, leaving a certain height. After an interval of 7 days, the wall should be repaired and tightly packed, and anti-cracking measures should be taken (adding nailed steel wire mesh or alkali-resistant fiberglass net and other materials).

5. During the masonry construction process, it is strictly prohibited to construct according to the drawings. If the wall is changed, there should be a change contact sheet from the design unit. The wall should not be built directly on the cast-in-place slab without beams at the bottom.

IV. Building energy-saving construction

1. Design changes involving building energy-saving effects should be submitted to the original construction drawing review agency for review and approval.

2. Wall insulation materials should hold local product promotion certification before they can be used in local projects.

3. The wall insulation thickness and construction methods should meet the design requirements. Especially around the window openings where the exterior walls are insulated, and the exterior walls of stairwells, kitchens, bathrooms, etc. where the exterior walls are insulated, are areas that are easily forgotten or not constructed. It is prohibited to cut corners or cut corners when external wall insulation is only constructed on the ground floor.

4. Energy-saving exterior windows must be constructed according to the drawings, and it is strictly prohibited to use ordinary aluminum alloy profiles instead of heat-insulating bridge aluminum alloy profiles. During construction, attention should be paid to the difference between steel-plastic windows and plastic-steel windows.

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