1, template demoulding adopts oily demoulding agent, the concrete surface is too smooth, and poor adhesion leads to hollowing and cracking of plastering surface.
2. The masonry assembly and construction methods are unreasonable, and the masonry settlement leads to hollowing/cracking of the plastering surface.
3. The seams made of different materials are not treated by hanging nets, or the hanging nets are unreasonable, resulting in air cracks.
4. The slotted surfaces of several pipelines are not blocked or blocked unreasonably, which leads to cracking of plastering surfaces.
5. Before plastering, concrete and autoclaved masonry are not sprayed or sprayed with poor adhesion.
6, plastering mortar mixing at will, mortar strength can not be effectively guaranteed.
7, mortar mortar additives such as mortar king, reduce the strength of mortar.
8, a plaster thickness is too thick (greater than 12mm) or layered plastering process interval is insufficient (less than 12 hours), plastering wall mortar slip, plastering layer prone to horizontal sag cracks, making the plastering layer on the wall appear empty drum;
9. The plastering finished surface is not maintained in time, and there is no effective water conservation measure.
10, the pipeline is installed with a slot behind the plastering surface, and the plugging method is unreasonable.
Second, the cause analysis and improvement of plastering hollowing and cracking
Cause analysis:
The use of oily or solvent-based release agent on the surface of the wooden model leads to too smooth plastering surface or residual oil residue on the surface, and poor adhesion, resulting in hollowing of plastering surface.
Practice of improvement:
Water-based release agent should be used for the demoulding of non-fair-faced concrete, and the demoulding time should be controlled, which not only ensures the molding quality of concrete, but also ensures the cohesiveness of concrete and reduces the risk of hollowing in the later period.
Cause analysis:
Tilting roof brick assembly is not dense, the angle of sloping roof is too large, and the sloping roof of long wall is assembled in the same direction, which is easy to crack in the later stage.
Practice of improvement:
Inclined roof bricks should be densely assembled, and the angle should be 45-60 degrees. When the wall is long, it should be laid in two directions, and the finished triangular block should be placed in the middle.
Cause analysis:
There is no horse tooth on the contact surface between the constructional column and the masonry, which reduces the seismic and crack resistance of the constructional column.
Practice of improvement:
The saddle fork of the constructional column retreats first, and the skin advances and retreats, leaving a length of not less than 6cm. Rachel reinforcement of constructional column is set every 50cm, and the length of Rachel reinforcement entering masonry is 500 mm ..
Cause analysis:
The low pile wall near the door is made of cement bricks without biting, and the low pile concrete has no reinforcement, so its crack resistance is poor.
Practice of improvement:
The short stack masonry wall near the door is difficult to construct and easy to crack and deform in the later stage. In order to improve the stability of short piles, cast-in-place structure can be used instead, and steel bars can be planted every 30cm.
Cause analysis:
The junction of different materials is not treated with hanging net; Galvanized mesh is directly pasted with cement mortar, and galvanized mesh arch.
And the crack resistance is insufficient.
Practice of improvement:
Concrete and sintered brick are fixed with insulation nails, and sand aeration is fixed with cement nails. When fixed, the galvanized mesh is flat and does not arch.
Cause analysis:
The first-line pipeline of painting is not blocked, the pipeline and masonry are not fixed, and the crack resistance is poor.
Practice of improvement:
After the pipeline installation is completed, the pipeline shall be fixed with fixing clips or cement nails. Before painting, the pipeline slot should be blocked in time. Anti-crack mortar can be used to block the slotting of single and double-line pipelines. The third and above pipelines are blocked with fine stone concrete and micro-expansive agent, and then reinforced with galvanized steel wire mesh.
Cause analysis:
The conduit groove is not deep enough, and the conduit exceeds the masonry surface after fixation, and the plastering surface is a weak part here, which is easy to cause cracking in this part.
Practice of improvement:
Strictly control the groove depth of the conduit, DN+ 10 mm ≤ groove depth ≤ DN+20 mm, groove width ≤ DN+20 mm ≤ DN+60 mm ... to avoid damaging the wall surface if the groove is too deep, and the groove is too small to block.
It is difficult to be dense.
Cause analysis:
The concrete shotcrete is not full enough, the strength is poor, and the shotcrete peels off a lot, which reduces the adhesive force and easily leads to plastering cracks.
Practice of improvement:
The concrete shotcrete is not full enough, the strength is poor, and the shotcrete peels off a lot, which reduces the adhesive force and easily leads to plastering cracks.
Cause analysis:
Paint mortar is mixed at will, and there is no fixed feeding ratio. The sand content of mortar is too high and the mixing is uneven.
Practice of improvement:
Clear the mix proportion of plastering mortar, set up effective metering facilities, strictly control the feeding ratio, set up a set of mortar test blocks for each batch and send them to a third party for compressive test, brush the construction with bedding face, and record the feeding ratio of mortar every two hours.
Cause analysis:
The use of mortar additives banned by the government such as mortar king reduces the strength of cement mortar and is easy to cause cracking and sand formation on plastering surface.
Practice of improvement:
In strict accordance with the laboratory ratio list, determine the mortar feeding and ratio, and prohibit the use of national orders such as mortar king.
Additives to ensure the strength of cement mortar.
Cause analysis:
Plaster survives once, and after brushing the thickness of the country again, cement mortar flows down, causing the plastering surface to crack.
Practice of improvement:
Strictly control the first plastering thickness and plastering interval. The single plastering thickness should be controlled within 1.2cm, and the plastering interval should be above 12 hours. Considering the effectiveness of management, it is recommended to brush the bottom rough ash and surface layer every other day.
Cause analysis:
Maintenance and water conservation measures after plastering, hot and dry weather is easy to cause cracking of plastering surface.
Practice of improvement:
In hot and dry weather, water should be sprayed on the plastering surface every four hours for a week. You can also use Sailite water retaining agent, and the maintenance time can be set once every two days.
Cause analysis:
Grooving behind plastering surface will easily lead to hollowing and cracking if the sealing method is unreasonable.
Practice of improvement:
Before plastering, the pipeline should be installed to avoid cracking of plastering surface caused by slotting behind plastering surface. If post-slotting is really necessary, the slotting depth and plugging technology should be strictly controlled.
The slotting depth behind the plastering surface should be controlled to be more than 2cm away from the plastering surface, and micro-expansive agent should be added to the plugging mortar. The plugging shall be completed in two times, and the interval shall be greater than 12 hours.
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