Cause analysis and Countermeasures for leakage pre

2022-08-01
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Cause analysis and Countermeasures for external wall leakage prevention of high-rise residential buildings

I. cause analysis of external wall leakage

external wall leakage of residential buildings with shear wall or frame shear wall structure is mainly manifested in the following four aspects:

1. Causes of water leakage from cracks between filled wall brick masonry and reinforced concrete frame beams and columns:

(1) materials. The temperature linear expansion coefficient of brick masonry and reinforced concrete of infilled wall is different. The temperature linear expansion coefficient of reinforced concrete is twice that of brick masonry. At the same temperature, the two materials produce different deformation and cracks at the joint of the two materials. Rainwater seeps into the room along the cracks under the action of wind pressure

(2) construction. The tie bar between the shear wall or column and the infilled wall is missing. In addition, when the infilled wall is built, the masonry is not easy to be embedded closely with the frame beam column, especially in the embedded part between the infilled wall and the beam bottom, which has neither connecting reinforcement nor easy to be filled and embedded tightly, so it is a frequently occurring part of cracks and water seepage

2. Infilled wall masonry seeps water along the gap between bricks. Porous bricks are commonly used for external walls in Shanghai. During masonry, the mortar of vertical head joint is often not dense; When the horizontal mortar joint is scraped, it is easy to flow into the brick hole; The masonry wall did not fully wet the bricks in advance according to the construction regulations, and the dry bricks quickly absorbed the moisture in the mortar, causing the mortar to dry shrink and crack. The most important one is that the vertical joints are not dense

3. The reserved holes for the through wall casing of the external wall, such as the through wall screw holes of the formwork outside the guarantee function and the reserved channel steel holes of the cantilever scaffold left during the construction of the water seepage external wall, are not dense when sealing the wall, resulting in gaps

4. The test results of the water seepage spray test around the window frame of the external wall show that the rainwater of the external wall mostly seeps into the room from the cracks between the window frame and the painting layer of the external wall, and is concentrated in the cracks between the window ceiling, the window sill, the vertical edge of the window frame and the painting layer of the external wall. The main reasons are as follows: the foaming agent silica gel is not dense, the window frame is not firmly installed, cracks are generated under long-term wind pressure, the pipe splicing connection in the combined window is not standardized, no drip tank is set at the ceiling, the window sill is flooded and the window frame is painted around to bite the window frame

II. Prevention and control measures for external wall leakage based on the above analysis, we have formulated a series of measures and carefully implemented them

(I) prevention and control of water seepage from cracks between infilled wall brick masonry and reinforced concrete frame beams and columns × two hundred × The wall is wide with an inclined angle of 60 degrees. After the wall construction is completed, the settlement is basically stable and the room has enough space (one week later), the inclined masonry can be carried out

2. Tie bars shall be reserved for the filling wall and concrete wall in strict accordance with the specifications. When painting, a 30cm wide steel wire sheet shall be used at the connection between the wall and the wall to ensure the consistency of product quality among different batches, with 15cm on each side, so as to ensure no cracks after painting

(II) prevention and control of water seepage of infilled wall masonry along the gap of brick joint "three one" masonry method shall be adopted in the construction of porous brick or three hole clay brick to ensure the compactness of vertical head joint mortar and horizontal mortar joint mortar. The bricks shall be fully wetted in advance in strict accordance with the construction regulations. During the construction, through our careful organization and careful construction, the plumpness of mortar was ensured. In the inspection and evaluation of high-quality structures in Minhang District, Shanghai, the plumpness of vertical and horizontal mortar joints of the walls of No. 27 and No. 28 buildings of Hangtian garden reached 951, but the user set more than% after completing the test data

(III) prevention and control of water seepage in the reserved hole of the wall bushing of the external wall

1. We have adopted four waterproof measures for the screw hole: during the structural construction, ensure that the screw hole is high inside and low outside; Before painting, block more than 5cm with foaming agent; When applying foaming agent, leave about 5cm holes on the outside and plug them with expanded cement; Finally, large areas of exterior walls are painted and paved with face bricks

2. For the reserved holes of cantilever scaffold, fine aggregate concrete mixed with expansive cement shall be used for blocking twice

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