The rigid waterproof roof is a waterproof layer made of ordinary fine stone concrete, compensated shrinkage concrete, and block rigid materials, and has the advantages of convenient construction, simple structure, wide source of materials, and low price, and is currently widely used. However, due to various reasons, some of the projects have some common defects such as cracking and splitting, which not only directly affect the function of the house, but also directly affect the durability and robustness of the entire building. This article briefly discusses the causes of cracks and leaks in rigid waterproof roofs and their prevention and control measures.
I. Factors that cause cracking and leakage of the waterproof layer
1.1 Causes of roof cracking or leakage due to temperature changes
(1) Due to the rigidity of the rigid waterproof layer, the ability to adapt to displacement deformation of the base layer is small, which can result in the cracking of the joint between the rigid waterproof layer and the structural layer and the cracking of the rigid waterproof layer by the structural layer. The temperature displacement of the component caused by temperature changes can also lead to cracking and leakage of the waterproof layer. There are two main situations. First, the horizontal roof components, affected by seasonal or daily temperature changes, horizontal displacement due to thermal expansion and contraction, then the waterproof layer cracking and leakage: the other is the vertical roof components Temperature difference between the upper and lower layers causes temperature difference, which causes inconsistent deformation of the upper and lower layer members, resulting in vertical deflection deformation displacement of the roof and cracking and leakage of the waterproof layer. Cracking and leakage of the waterproof layer caused by temperature displacement are common in severe cold regions.
(2) Changes in atmospheric temperature and changes in solar radiant heat cause thermal expansion and contraction of the roof, resulting in thermal stress. When the temperature dividing joint is not set or set unreasonably according to regulations, it cannot effectively eliminate the influence of temperature stress and make the rigidity. Waterproof roofs produce temperature cracks and leak when they are affected by rain and snow.
(3) The roof waterproofing layer made of fine stone concrete has a relatively large thickness (generally greater than 40 mm). For such a certain volume of concrete, the heat of hydration of the cement and the heat storage inside the concrete will be stored for a long time. In (generally 30 ~ 60d), so that there is a temperature difference effect with the ambient temperature, so that the concrete produces temperature cracks, causing roof leakage.
1.2 Causes of Cracking and Leakage of Waterproof Layers by Other Factors
(1) Displacement displacement of the joint due to uneven foundation settlement and deflection difference leads to cracking and leakage of the waterproof layer.
(2) The deformation of the roof plate caused by the action of the load causes deformation, resulting in displacement of the joint and cracking and leakage of the waterproof layer.
(3) Evaporation of absorbed water or free moisture inside the concrete causes the concrete to cause physical and wet deformation and displacement, resulting in cracking and leakage of the waterproof layer. If the proportion of concrete is not properly designed and the ratio of water to cement is too large, the excess water gradually evaporates during the hardening of the concrete to form many gaps and coherent capillary networks, which become the water seepage channel of the roof; and excessive water is in the sand and gravel. On the surface of the aggregate, a layer of free water is formed and capillary channels are formed between them. Under the effect of drying, the water in the pores escapes to generate capillary pressure, causing the concrete to shrink in a 'capillary shrinkage' state. Surface cracking.
(4) The rigid roof is exposed to the atmosphere for a long time. Under long-term sunlight and rain, the carbonization phenomenon will occur on the concrete surface layer, which will cause the waterproof layer to crust, sand, and cause leakage.
1.3 Poor construction quality leads to roof cracking and leakage
(1) The vibrating concrete is not compacted during construction, the light collection and calendering are not good, and the early drying and dehydration and improper maintenance in the later period reduce the compactness and waterproof impermeability of the concrete structure, leading to roof leakage.
(2) During construction, the temperature is too low or too high to cause leakage or cracking of the concrete rigid waterproof roof. When the temperature is too low, the concrete length grows slowly. When the temperature is negative, the concrete is frozen, causing its strength to decrease and the internal structure to break or freeze, losing its waterproof effect and leading to leakage. When the temperature is too high, it will be exposed to the hot sun. Under the construction, the moisture of the concrete will evaporate too quickly, resulting in shrinkage cracks and leakage.
(3) The waterproof layer did not find slopes or locate slopes in accordance with design requirements, resulting in local accumulation of water and easy leakage in the area of ​​accumulated water.
(4) The concrete waterproof roof has high rigidity and poor ability to coordinate with the grassroots. When the waterproof layer is too thin, due to the change of the base layer, the waterproof layer cracks, cracks occur, and leakage occurs.
(5) The deformation joint waterproof structure, the waterproof structure extending out of the roof pipe, the flooding structure, the waterproof structure of the dividing joints, and the water-proof roof structure treatment do not meet the specification requirements, resulting in leakage of the roof; in addition, due to the parapets, gables and The deformation of the roof panel is inconsistent. If the detailed construction of the joint is not handled properly, it is also easy to crack at the intersection and form a leak.
(6) The basic process of roof caulking is not taken into account during construction. Prior to caulking, the sand, stone chips and other inclusions in the seam are not removed and the caulking is not dense, leading to roof leakage; in addition, caulking material The adhesiveness, flexibility and anti-aging ability are poor and cannot adapt to the deformation of the waterproof layer resulting in cracks.
Second, prevention and control measures
Based on the above causes of cracking and leakage of the rigid waterproof roof, the following preventive measures can be taken.
(1) When selecting a rigid waterproof design scheme, the structural type should be determined according to the requirements of roof waterproofing facilities, regional conditions, and architectural features. Generally in the non-loose material insulation layer and the roof temperature difference area, the choice of ordinary fine stone concrete waterproof layer; in the structure of the larger change of the base layer, should use the shrinkage of concrete as a waterproof layer.
(2) The joints between the rigid waterproof layer and the upper wall, the parapet wall and the protruding roof structure shall be reserved strictly according to the requirements (30mm), and shall be flexible sealed. In the junction between the roof plane and the facade of the gap to leave a groove, and carefully handled to prevent the rigid waterproof layer due to temperature deformation, volume expansion when the daughter wall to push cracks and cracks in the damaged part, causing leakage.
(3) Ordinary fine stone concrete waterproof layer and compensation shrinkage concrete as waterproof layer, and the base layer should be strictly done between the isolation layer, select the isolation layer material to completely separate the waterproof layer from the structural layer, to the maximum extent to avoid the structural layer and waterproof Between the layers due to temperature, wet and dry, load, settlement and mutual implicated, so that the waterproof layer is deformed by structural layer cracking.
(4) Before the construction of the concrete waterproof layer, the slope shall be in strict accordance with the design requirements, and the parts that do not meet the requirements of the slope shall be seriously treated, and the waterproof layer shall be constructed after reaching the design requirements.
(5) Ordinary fine stone concrete waterproof layer should use ordinary portland cement, the maximum particle size of coarse aggregate should not exceed 1/3 of the thickness of the waterproof layer, fine aggregate using medium sand or coarse sand, concrete waterproof layer suitable Participate in admixtures such as water reducer and water repellent agent to improve its waterproof and impermeability properties. Accurate admixture metering should be done properly and the feeding sequence must be properly mixed. When making the waterproof layer for shrinkage-reducing concrete, infiltration should be strictly in accordance with requirements. Expansion agent, and careful calculation of infiltration, may not cut corners.
(6) The concrete mixing time should be not less than 2min; if there is leakage and segregation during transportation, it must be re-stirred; the concrete in each partition plate must be poured once, and the construction joint is strictly prohibited. The thickness of the concrete waterproof layer should be uniform. The pouring should be done strictly according to the requirements of vibrating, compacting and leveling. When the water is collected, it should be secondarily polished to make the internal and external strength and shrinkage inconsistent, resulting in shrinkage, cracking and moulting of the surface layer. Waterproof effect.
(7) In order to prevent concrete from causing dry shrinkage cracks due to early dehydration, it should be timely cured after the final setting of the concrete, and ensure that the fine stone concrete is in a fully wet state before reaching the design strength, and it should be necessary at the initial stage of conservation. Establish warning signs in obvious positions.
(8) It is necessary to focus on the waterproofing of detailed structures. Before the construction, technical disclosure should be done carefully. During the construction, the construction process must be strictly followed, and every process must be strictly inspected. If the requirements are not met, the next process must not be allowed. To ensure construction quality. After the construction of the waterproof layer is in contact, the water storage time must meet the requirements if there are conditions for the impoundment experiment. If there is no condition for the impoundment test, the technicians should carefully inspect the roof after the rainy days before the project is delivered for use. Water-repellent effects, where leakage is found, should be dealt with immediately.
(9) The construction of concrete waterproof layer shall be strictly prohibited under the conditions of extreme heat, severe cold, rain, snow, and sand, so as to prevent the concrete from freezing or shrinkage and produce cracks and reduce the waterproof effect.
(l0) Split joints of concrete waterproof layer Before joint construction, the debris in the partition joints shall be carefully cleaned, and caulking materials with good sealing performance, adhesion, flexibility and anti-aging ability shall be selected.
Third, the conclusion
Due to different climatic conditions in different areas, differences in local waterproof materials, and differences in construction technology and construction levels, the waterproofing methods for roofing are not always the same, so the causes of cracking and leakage of concrete rigid roofs are also different. Should be treated differently.
Statement: The article comes from the waterproof material investment network → http://Technology/Construction/news_Show.Asp?Hid=6139
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