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Prevention and treatment of leakage of concrete structure in the basement

jiu0 edited on2017-06-07 05:17:25 35 views

Prevention and treatment of leakage of concrete structure in the basement

I. overview

With the increase of high-rise buildings, whether the office building, large shopping malls and commercial and residential buildings, generally have a large area of parking lot, civil air defense requirements and equipment room and other basement structures.
Basement leakage is also common, leakage not only affect the use of the function will also reduce the durability of the building.
Some successful experience of basement seepage prevention work, now refer to.

Ii. main causes of cracks

1. design reasons

① ( method - 89 ): the maximum spacing of the expansion joint of cast-in-situ reinforced concrete wall shall be 20 ( open air ) - 30m ( indoor or soil ), but the wall length in actual engineering exceeds this stipulation.

② the self - waterproof function of the structure and no flexible waterproof additional layer are not provided.
In the design of self - waterproof concrete itself water leakage: because of the complex structure, such as the reinforcement of the reinforcement, foundation settlement difference, the waterproof concrete may also cause leakage. Therefore, the high water level area design of the basement waterproof best waterproof line.

③ the waterproof layer is only provided in the external facade of the retaining structure, which causes the waterproof layer and does not reach the whole sealing state, resulting in leakage.

④ when designing the basement, the outer reinforcement protective layer on the outside of the floor and outside of the outer wall does not set the protective layer according to the specifications and thickens appropriately.

( 5 ) the designer considers not thorough, and only considers no ground water in the design of building basement waterproof on hillside, ignoring the leakage of rainwater to basement floor and wall.

2. causes of construction

( 1 ) the material of flexible waterproof layer is unsuitable and the construction quality is poor, including waterproof construction to meet the requirements of the basic level. In
The corner is not strengthened, in the wall pipe fittings, embedded parts, deformation joints and other parts of the improper treatment, the coil and coil overlap is not strong reasons.

( 2 ) long - term exposure to the basement wall: it is difficult to realize the backfill and top cover immediately after the wall is completed. this kind of thin and long structure is sensitive to temperature and humidity changes, and often causes the wall cracking due to additional temperature shrinkage stress.

( 3 ) excessive temperature difference

Including the influence of large temperature difference between inside and outside of concrete foundation slab, temperature difference between day and night, premature dismantling and climate change.

( 4 ) poor quality of concrete construction

Poor quality of raw materials, inappropriate mix proportion, improper use of additives ( such as micro - expansion agent, pumping agent, etc. ), poor slump control, any water added in the construction and poor maintenance of concrete will lead to cracks in concrete shrinkage.

In addition, in the basement foundation construction, the construction scheme is not considered comprehensive, the concrete layered pouring interval is too long, resulting in the pouring of upper concrete, the lower layer concrete has been early setting, forming the construction cold joint.

( 5 ) the construction treatment at the deformation joint is unsuitable and the waterproof weak point is formed

( 6 ) leakage caused by improper operation during the construction process

① the thickness of the protective cover is not enough to cause leakage: the external groundwater enters the surrounding reinforcement of the bottom slab through a thin protective layer of the outer side of the floor, and the corrosion of the reinforcement makes the concrete have cracks, and the direction of the reinforcement is seeping into the basement.

( 2 ) water leakage is caused by improper treatment of wall - through - wall bolt: the wall - wall bolt water seal plate is not welded tightly, or the wall bolt stays too long when the outer wall is cut, the external plastering is not strict, especially the steel bar is exposed outside the plastering layer, and the waterproof layer is worn through waterproof layer, chemical corrosion is formed under ground water, and water leakage is caused by corrosion in the interior wall.

③ water leakage in the reinforcement area of the external wall: water leakage occurs in the reinforcement concentration area of the external wall column and the corner roof. the reason is that the space is small, the pouring and ramming is difficult, and the concrete is not easy to be dense, resulting in leakage.

④ leakage of steel pipe joint is not easy to form leakage: the concrete embedded telecommunication pipeline and lighting pipeline etc., due to the rough surface of the steel pipe joint, underground water enters the concrete, and from the steel pipe joint into the pipe, the inner wall junction box is leaking into the room, or water seepage to the room along the steel pipe.

⑤ water leakage of the late poured band and leakage at the interface between the wall and the floor. there are humid and dripping phenomena at the junction of the wall and the ground and the surrounding part, and there are leaking points at the junction.

⑥ the influence of construction management and other factors, mainly reflected in the unreasonable arrangement of construction process and poor management. The wall or floor of the wall or floor with waterproof requirements is free with openings and pipes, but the waterproof repair process is not carefully carried out, resulting in leakage.

Iii. preventive measures for leakage in the basement

1. design aspects

( 1 ) the expansion joint and late poured band shall be reasonably arranged: the cast-in-situ structure of the basement shall be provided with expansion joint when the length exceeds 30m. Late poured band is a common method that has been proved to be effective in controlling cracks in concrete structure.

( 2 ) admixture or admixture in concrete. The expansion agent is mixed into concrete to compensate the shrinkage stress of concrete.
Or in the concrete, the fiber ( such as PP fiber, etc. ), the fiber has certain tensile strength, and the concrete grip strength, to strengthen the tensile stress in the process of concrete hardening, and control the production of concrete cracks.

( 3 ) anti - cracking reinforcement is provided to increase the structural reinforcement and improve the cracking resistance. the small diameter and small spacing should be used in the horizontal reinforcement of the outer wall of the basement so that the structure reinforcement can reach temperature reinforcement, and can effectively improve the crack resistance performance.

2. construction aspects

( 1 ) rational choice of the use of raw materials.

① the cement shall use the cement with low hydration heat, and shall give priority to the slag portland cement with strength grade 42.5, and the appropriate amount of ultra-fine fly ash and high efficiency water reducing agent, can reduce the amount of cement and capture the ke of high concrete.

② the sand shall be in clean medium sand, and the silt content in the sand shall not exceed 3 %. And through careful trial and trial, to improve the strength of concrete.

( 3 ) gravel or gravel shall be used for gravel;

④ admixture and admixture, the use of water reducing agent can improve the workability of concrete mixture, and can reduce water cement ratio, reduce water consumption, prevent the excess moisture in concrete can replace part of cement, reduce hydration heat, reduce concrete temperature and shrinkage crack.

( 2 ) the determination of main parameters of concrete mix proportion is strictly controlled.

① the slump shall be used according to different parts of the basement and construction technology to select different slumps. Strictly control the amount of cement and admixture and admixture. In order to make the mixture have good workability, the amount of fine aggregate must be guaranteed, and the trial blending shall be conducted according to the field requirements.

② strictly control the water cement ratio: the water-cement ratio is too large, the shrinkage rate of concrete is large and the impermeability is poor.

③ mix proportion shall be selected by laboratory.

( 3 ) conservation

After the concrete is poured, it must be covered with thermal insulation within 12 hours. after that, the concrete surface shall be continuously humidified for 14 days. In order to prevent the occurrence of dry shrinkage cracks and temperature cracks, the best surface has to take measures to maintain moisture and moisture conservation. For mass concrete, take effective temperature control measures, do a good temperature measurement record, control the internal and external temperature difference ≤ 25 ℃.

Iv. construction process control of basement leakage

1. the formwork shall be firm and tightly jointed. no grout shall be leaked. The deformation or leakage of the template is easy to cause water leakage. The tensile bolts of the template shall be welded to the sealing ring.

2. concrete pouring. In order to avoid stratification and segregation of concrete, the free fall of the mixture shall be strictly controlled during pouring. The pouring can be carried out by separate sections, but attention should be paid to the layer and layer, the interval between segment and segment shall not exceed the initial setting time, so as to avoid the construction joint.

3. improve the quality of concrete vibration. The basement concrete shall be vibrated in a comprehensive manner, and the cutting material and vibration shall be formed in a certain order to prevent the leakage and vibration. In order to complete the upper layer concrete pouring vibration before the initial setting of the concrete, the vibrator shall be inserted into the lower layer concrete 5 - 10cm to ensure the quality of the concrete in the layer. In order to strictly control the vibration time, the concrete shall start with the pan pulp and the bubble shall prevail, and shall not be owe or super.

4. treatment of individual special parts

( 1 ) treatment of construction joints

The construction joint of the external wall shall be located on the outer wall of 30cm above the floor. For the basement construction joint, the water sealing steel plate or the design shall be set aside according to the design. Before placing the concrete, excavate the floating pulp of the original concrete surface and carefully clean it and then pour the new concrete. The concrete of the late poured band shall be compensated by shrinkage concrete.

( 2 ) processing of embedded parts

Penetration of the embedded parts of the external wall shall be added to the waterstop ring on each embedded part. The penetration template of embedded parts shall be tightly closed, and no grout shall be leaked. When pouring concrete, pay attention to the concrete vibrator under the embedded parts, so as to prevent voids and Cellular.

V remedial measures after leakage in the basement

1. the principle of plugging: the leakage point and the leakage line must be identified through the ti to prevent plugging. Adopting the method of rigid - flexible combination and expansion enhancement; The leakage of the embedded parts around the plugging, after the gouging certain depth, the use of accelerator plugging.

2. processing methods

At present, the common basement concrete wall crack treatment methods have the following four categories: a, surface smearing method; B surface brushing and glass fiber cloth method; C, filling method; D, grouting method. Commonly used for the third and fourth methods, such as combining two methods to use, the effect is better.

( 1 ) filling method

Using steel or high-speed rotating cutting disc to expand the crack, form v - shaped or trapezoid groove, clean the clean layer pressure wipe epoxy mortar or cement mortar, asphalt ointment, polymer sealing material or various finished products sealing material sealing cracks. When the repaired crack has structural strength, it shall be filled with epoxy mortar.

( 2 ) grouting method

The grouting materials commonly used include epoxy resin, methyl methacrylate, propyl alcohol, cyanogen coagulant and water-soluble polyurethane. The epoxy materials are widely used, and the construction is convenient. The grouting method is generally used in the following two categories: one is to inject the epoxy resin grout into the cracks with low pressure, sealing the cracks and no obvious trace after repair; Another category is pressure grouting.

Vi. overview

In the actual construction, the principle of prevention should be adopted from the design and construction process, and the construction quality should be strictly controlled to ensure the waterproof effect of the basement.

url:http://www.aneave.com/p835
published on:20170607 05:17:25 guangzhou

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