After using water stop (water stop steel plate, water stop), water can be prevented from infiltrating into concrete, which plays a dual protection role of waterproof and water stop.
Theoretically, water stop, rubber water stop and water stop steel plate can effectively prevent external moisture from infiltrating into concrete through construction joints. From the analysis of water-stop principle and construction technology, there are still great differences between them, and the effect is different. Taking a three-story underground structure of a project as an example, this paper analyzes the advantages and disadvantages of using them in different parts.
Water-stopping principle: the water-stopping belt stops water by absorbing water, expanding and squeezing with concrete to block the gap.
Construction technology: the water stop is a square strip, and parallel lap joint method is adopted when connecting, and no breakpoint can be left in the middle. For convenience, construction units often like to use water stops. After concrete pouring is completed, it can be pressed on the concrete pouring surface of the wall or reserved with grooves for secondary inlay.
Advantages and disadvantages analysis: simple construction, less investment and more economical. But the water-stop effect is not as good as that of water-stop hose and water-stop steel plate. There are many unforeseen problems in the construction process. First, the reinforcement is not well placed. Second, too long time, moisture absorption and expansion, affecting the effect, especially in the rainy season, the air humidity is high, there is more rain, and the water stop effect is even worse. Third, the construction joints are uneven and have poor contact. Usually, the effect of this method is not ideal. For example, when the water stop is installed, the groove is too big to be effectively fixed and too small to be embedded. When concrete is poured, it is easy to shift under the buoyancy of concrete.
Scope of application: It can be used for waterless underground buildings, generally used for secondary parts of buildings or parts with lax requirements, such as basement exterior walls and foundation rafts above groundwater level, mainly to prevent capillary water in soil layers. Even if water leaks, it has little impact on the building, which can be quickly solved by waterproof materials such as plugging agent, but it is not suitable for underground garage roofs with covered soil or planted soil on the surface.
Second, the water stop steel plate
Water-stopping principle: the "opening" of the water-stopping steel plate faces head-on, and the steel plate is closely combined with concrete, supplemented by the splayed shape of the steel plate, so it is difficult for groundwater to penetrate from the steel plate along the construction joint.
Construction technology: the thickness of water-stop steel plate is generally 3㎜, the width is greater than 200 ㎜, and the length is generally processed into 3 meters or 6 meters, generally 3 meters, which is convenient for transportation. During construction, try to ensure that the water stop steel plate is on the center line of the wall; The welding between two steel plates shall be fully welded on both sides, and the overlap of steel plates shall not be less than 200mm. The corner of the wall is usually treated by bending the whole steel plate, T-welding and 7-shaped welding. The support welding of water-stop steel plate can be welded on the main reinforcement with small steel bars; When the water-stop steel plate passes through the column stirrup, the stirrup can be disconnected, made into an open hoop and welded on the steel plate.
Advantages and disadvantages analysis: the connection part of steel plate water stop requires full welding, which is of course good, but the cost is much higher and the construction speed is slower. According to the specification, the wall thickness of shear wall with water-stop steel plate should not be less than 250㎜, and the clear distance between water-stop steel plate and steel bar is: wall thickness /2- outer protective layer thickness 50- wall two-way steel bar diameter; When the wall thickness is 250, 250/2-50-30 = 45mm2. The distance between the water-stop steel plate and the wall is small, and the concrete is easy to leak vibration in this part during construction, forming honeycomb holes. Therefore, when using water-stop steel plate, vibration must be strengthened at construction joints. The weak links of this water stop measure are the overlapping part and the 90-degree corner part. It is very difficult to control the 90-degree fillet weld of steel plate, and it is easy to form water leakage points. The welding construction at the corner of steel plate should be controlled as the key link of this process.
Scope of application: It is suitable for structures with groundwater, such as pools and other structures with water, as well as horizontal and vertical construction joints buried below the groundwater level.
Third, rubber water stop.
Principle of water stop: The water stop is made and installed to prevent water from penetrating, and its width ranges from 200 to 350. According to the design selection, the seepage diameter should be appropriately lengthened. In the process of concrete pouring, it is partially or completely embedded in concrete, which has certain strength and toughness, and its strength and toughness are between the water stop and the water stop steel plate.
Construction technology: the fixing method of water stop includes additional reinforcement, special fixture, lead wire and formwork. If perforation is needed, only the installation area at the edge of the water stop should be selected, and other parts should not be damaged. If field connection is required, the electric heating plate can be vulcanized or cold bonded (rubber water stop) or welded (plastic water stop). Water stop construction shall not be exposed in the open air for a long time to prevent rain and contact with highly polluting chemicals; During transportation and construction, prevent machinery and steel bars from damaging the water stop; In the process of construction, the water stop must be reliably fixed to avoid displacement when pouring concrete and ensure the correct position of the water stop in the concrete;
Advantages and disadvantages analysis: there are many sharp stones and sharp steel bars in concrete. Because the tearing strength of plastic and rubber is 3 ~ 5 times lower than the tensile strength, once the water stop is punctured or torn, the crack will expand without great external force. Therefore, in the process of water stop positioning and concrete pouring, attention should be paid to the positioning method and pouring pressure to avoid the water stop being punctured and affecting the water stop effect.
When pouring concrete, the water stop is a rubber product, which is soft, easy to deform and not straight, and it is difficult to control the width up and down. Binding lead wire to steel bars will damage the water stop, so the construction unit generally finds it troublesome and doesn't like to use it.
Scope of application: Waterproof material has good elasticity, wear resistance, aging resistance and tear resistance, strong deformation adaptability and good waterproof performance, and the temperature range is -45℃ ~+60℃.
The choice of water stop should be determined according to the important grade of structure, deformation of deformation joint, water pressure, working environment and economic factors. It is generally used for vertical water sealing in waterproof parts, such as construction joints, settlement joints and expansion joints of post-poured strip or slab-wall structures with large settlement deformation.
Four. Concluding remarks
Through analysis and comparison, it is found that among the three water-stop measures, the water-stop belt is low in cost, convenient in construction and the worst in water-stop effect, and is generally used in secondary waterproof parts above groundwater level; Water-stop steel plate has the highest price, the most difficult construction and the best water-stop effect. Generally, it is suitable for vertical and horizontal construction joints below the groundwater level, but it is not suitable for parts with large deformation due to its high stiffness. The price, performance and construction difficulty of water-stop are between water-stop and water-stop steel plate, and the application scope is wide. Because of its toughness, it is more suitable for parts with large deformation and settlement deformation requirements.