With the continuous progress of science and the continuous development of construction industry in China, high-rise buildings are appearing in people's lives with lightning speed. However, it is the development of high-rise buildings and the continuous improvement of people's requirements for building space that makes the underground engineering and underground comprehensive waterproof engineering of high-rise buildings pay more and more attention. The quality of underground waterproofing works of high-rise buildings will not only have a great impact on the effective use of buildings, but also have an important impact on the structural safety and service life of high-rise buildings to a certain extent.
First, the important significance of waterproof engineering quality in basement of high-rise building
The waterproofing of high-rise buildings is stricter than that of general construction projects. It is an important function of building products, which not only relates to the environment and sanitary conditions where people live and use, but also directly affects the service life of buildings.
The walls and bottoms of basements of houses and underground structures that are not allowed to enter water are buried in wet soil or soaked in underground water for a long time. So do moistureproof or waterproof treatment. Moisture-proof treatment is relatively simple, and waterproof construction is more complicated. In high-rise buildings or super-high-rise building projects, one or more basements are generally installed due to the setting of deep foundation or the needs of building functions, and its waterproof function is very important.
Cause analysis of basement leakage
1) When concrete shrinks and hardens in air, its volume decreases, which may lead to cracking of basement concrete and destroy its waterproof effect. The shrinkage of general concrete is 0. 15%. Volume shrinkage of concrete is mainly lifting shrinkage and drying shrinkage, while cold shrinkage is caused by heat loss or temperature drop in concrete. Dry shrinkage is caused by water release or temperature drop in concrete, and shrinkage is closely related to temperature change.
2) uneven settlement of the structure will destroy the basement waterproof layer. After the structure bears the upper load, it will produce uneven settlement, and some external waterproof layers and protective walls that can reach 20~40 construction can not play a waterproof role with the settlement of the structure. The corners of linoleum are often weak links and easy to leak. However, the waterproof linoleum is attached to the protective wall in advance, and the structure is very tight when it settles. When the protective wall does not fall down, the waterproof layer of linoleum will be more seriously damaged by tension when it falls down with linoleum. Due to the leakage of basement, the basement engineering structure with outdoor window wells has more settlement and less window settlement. Uneven settlement is caused, and the waterproof layer of linoleum at the contact between window well and external moisture is damaged, which affects its waterproof effect.
3) The impermeability of concrete is closely related to the gradation of concrete. When the concrete is poorly graded and has poor workability, it is prone to segregation and poor impermeability during construction, and the sand and gravel are contained according to the silt content. Excessive impurity content will also greatly reduce its impermeability: the impermeability of concrete is closely related to vibration, because the quality of vibration directly affects the compactness of concrete. If the operation procedures are not carefully implemented at concrete construction joints, artificial construction joints will also become weak links, and water will often penetrate into them.
4) The basement waterproof layer is not constructed according to the operation procedures. For example, the linoleum laid at the lap joint of the coil is not tight, and the strengthening measures at the corner are often ignored. Water objectively enters the room from these weak points, especially the waterproof layer at the wall-penetrating pipeline and the expansion joint structure at the entrance and exit of civil air defense. Once improperly operated, it will greatly affect the waterproof effect of the basement.
Three, we mainly grasp the following points in the construction:
3. 1 Strictly control materials.
As the saying goes, "materials are the foundation", the following points should be guaranteed for materials: the variety of materials must meet the design requirements, the quality sampling of materials must be qualified, and there must be a factory certificate and a permit.
3.2 The core of the overall waterproofing of the basement is to grasp the self-waterproofing of the structure, so as not to make the local self-waterproofing of concrete fail. The core of the so-called structural self-waterproofing is that the final poured structural concrete reaches the design strength, meets the requirements of impermeability and corrosion resistance, and has a compact structure and no harmful cracks. Concrete is a porous material. It is often unsatisfactory to improve the impermeability of concrete only by grading stone, increasing cement content and sand ratio, and adding silicone or water reducing agent to reduce the voids and pores of concrete, which is due to ignoring the fatal weakness of concrete-shrinkage. Although concrete is dense, the shrinkage (temperature difference shrinkage) caused by drying and cooling will cause cracks in the structure, thus destroying the overall waterproof function of the structure. With the development of concrete admixture application technology, concrete waterproof technology has reached a new level, especially the appearance of shrinkage-compensating waterproof concrete, which overcomes the defects of low tensile strength and small ultimate tensile strain of ordinary concrete.
3.3 The dust and oil stains on the dry powder concrete cushion on the basement floor must be cleaned up, and there can be no Mingshui. According to the advancing speed of concrete pouring, dry powder is spread on the cushion 0.5h before concrete pouring, and the dosage is 1.2 ~ 1.5kg/m2. During construction, before concrete pouring, the uniformity of floor dosage should be quantitatively controlled by region. Fourth, strengthen the waterproof treatment of special construction parts. 4. 1 construction joint treatment
The treatment of construction joints is one of the keys to the success or failure of basement waterproofing project, and improper treatment will fall short. Try to avoid the appearance of construction joints in engineering construction. When the seam between the bottom plate and the wall must be preserved, tongue-and-groove and steel plate water stop (-300mm×2mm) should be adopted. The method is to insert the tenon after the concrete pouring of the bottom plate is completed and the board wall rises (200mm high). Steel plate welding requires full welding, and the steel plate strip is embedded in the upper and lower parts of concrete. After construction, the seepage path can be increased to achieve the purpose of seepage control.
4.2 Treatment of Embedded Iron Parts
In the design, the anchorage of embedded iron pieces is generally straight, and sometimes its length is close to the thickness of the structure, which will also cause water seepage.
4.3 Wall bolt water stop treatment
In the construction of concrete wallboard structure, it is necessary to use opposite bolts to fix the formwork, but in the construction of basement wallboard, it is easy to form seepage points and destroy the self-waterproof effect of concrete structure. Bolts with welded water-stop rings are adopted in the basement exterior wall construction of this project, which overcomes this shortcoming. After concrete pouring is completed, dismantle the formwork, cut a gap of about 20mm at the root of the opposite bolt, burn the bolt end rod with gas welding, and block the gap with waterproof mortar to eliminate the leakage point and achieve the waterproof purpose.
4.4 Post-cast strip and water stop can be used for waterproof treatment.
In some high-rise buildings, due to the needs of function and modeling, the main building of high-rise buildings is often connected with the podium of low-rise buildings, which surrounds most of the main building. From the traditional structure, it is hoped that the high-rise building will be separated from the podium, which requires setting deformation joints; But from the architectural requirements, I don't want to set seams. Because there will be double beams, double columns and double walls when setting joints, the plane layout is limited, so the construction post-pouring belt method came into being. Post-pouring zone of building is divided into post-pouring zone settlement zone, post-pouring zone contraction zone and post-pouring zone temperature zone, which is used to solve the problems of differential settlement between high-rise main building and low-rise podium and reduction of temperature stress caused by shrinkage deformation of reinforced concrete. This kind of post-cast strip generally has many deformation joint functions, and one function should be given priority to in design, supplemented by other functions. 4.5 Adopt new waterproof materials with good performance and reliable quality.
This is the guarantee to improve the quality of waterproof engineering. Before construction, it is necessary to collect the performance and use information of various waterproof materials, and choose waterproof materials with convenient construction and excellent performance. Waterproof materials entering the site must be checked to see if they meet the design requirements, with factory certificate and use certificate, and can only be used after passing the sampling test. The construction party shall assign special personnel to check and accept the working procedure, and follow up the quality monitoring of the working procedure. After each working procedure is qualified, it can be transferred to the next working procedure. In the case of deep basement, high groundwater level and high impermeability requirements, multi-layer composite waterproof measures should be selected in the design. On the premise of structural waterproofing, multi-layer flexible waterproofing can be used for the outer wall of the basement, layered rammed soil around the outer wall of the basement, and five layers of flexible waterproofing can be used for the inner wall, which can achieve better waterproof and impermeability effects.
4.6 wall pipeline treatment
Generally speaking, there are many pipes installed through the wall in the basement of this project, and most of them are below the groundwater level, so waterproof should be done during construction. Before pouring concrete structure, the casing should be retained at the wall-penetrating pipeline, and the water stop ring should be welded on the casing. When pouring, the concrete around the casing shall be vibrated and compacted. V. Conclusion
To sum up, the basement waterproofing project of high-rise building is related to the stability and service life of the main body of the building structure. Only by strictly controlling the construction quality in the construction process, that is, controlling the construction quality of waterproof concrete, controlling the construction quality of detailed waterproof projects and protecting the finished products of waterproof projects, can the construction quality of basement waterproof projects be truly guaranteed, thus effectively avoiding the occurrence of such common quality defects.
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