Design reason
(1) according to the geological survey data, design a reasonable waterproof scheme. When the design unit does not know the environmental conditions of the site according to the data and documents of site investigation, it will ignore the design of waterproof engineering; Some designers directly quote the national waterproof design standards and atlas, ignoring the requirements and measures related to waterproof, and will not contact the actual engineering design drawings, resulting in the deformation of the building after the completion of the project, resulting in the rupture and leakage of the water stop.
② The design unit ignored the importance of waterproof engineering and directly applied the atlas and standards of waterproof design for expansion joints. The design unit did not consider the site environment, and the consequence of directly applying the atlas was that the waterproof effect could not meet the design requirements. For example, in the basement waterproof design, the function of squeezing the expansion joint water stop was not considered, which led to the water stop breaking and leaking.
(3) The uneven settlement of the building is not considered in the design, which leads to the tearing of the waterstop. The uneven settlement at the expansion joint is not considered in the structural design and calculation, and the waterproof effect is poor when the water stop is set.
Construction reason
(1) The quality of water stop is unqualified. When the materials enter the site, the acceptance management is not done well, which causes problems such as quality defects of the materials entering the site, which leads to the failure to meet the design requirements and the rupture of the water stop.
(2) The construction technology of water stop during installation is incorrect. During the construction, the quality control of the water stop is not carried out, which leads to the separation of the contact surface or the generation of bubbles, which makes the connection between the water stop and the concrete not dense and cannot form a sealed waterproof ring.
③ The water stop is not fixed or the fixing method is incorrect. The water stop is not fixed before concrete pouring, which leads to the water stop being flattened, twisted or even squeezed out of the wall by concrete, and the water stop cannot play a role in preventing leakage.
(4) The shrinkage of concrete is too large, which causes the waterstop to break beyond the ultimate stress. The mix design of concrete construction is unreasonable, and the ultimate tensile stress of the water stop is exceeded when the concrete shrinks in the later stage, resulting in stress concentration and tensile cracks.
2 treatment measures
2. 1 material control
Construction units should do a good job in material acceptance management system. Conditional units can use computers for management, which is convenient for material managers to comprehensively monitor the quantity, specifications and quality of materials. When selecting materials in the building materials market, the project material purchaser can bring an experienced technician to select materials. When selecting materials, the purchasing personnel must know the detailed specifications and technical parameters of the water stop, so as to know fairly well and appropriately reduce the material purchasing cost. For the water stop with special requirements, it is necessary to order from the manufacturer to ensure that it meets the national specifications and design requirements.
The material management personnel at the construction site shall check the model, quantity and specifications of the water stop, and keep the quality certificate. In order to ensure that the water stop used meets the design requirements, the water stop must be sampled and reinspected before construction to ensure that the size deviation and center hole deviation of the water stop should be within the range required by the specification; The surface is not allowed to have unqualified phenomena such as lack of glue, cracking and delamination; The quality of water stop ring meets the requirements, etc.
Do a good job in the protection and heat preservation measures of water stop and other materials, to prevent the sun exposure, cross storage with organic solution and other problems that damage the quality of water stop, and ensure that the quality of water stop meets the requirements before use; In the construction, in order to ensure that the exposed water stop is not damaged, the water stop can be wrapped with straw rope, and then the water stop can be overhead with a horse stool.
2.2 Construction control
1) fixing of water stop. The water stop will deform and expand in volume under various loads, so it can play a sealing and waterproof role. According to the construction method, the construction of water stop can be divided into embedded type and detachable type. (1) embedded water stop installation and fixation. Buried type means that the rubber water stop is partially or completely buried in the concrete during the concrete pouring process. Before binding reinforcement, the position line of expansion joint should be popped up on the cushion or lower concrete to determine the position of expansion joint. In the formwork supporting process, ensure that the positioning line is outside the formwork, which is used to detect the deviation of the water stop. After the steel bars are bound, place the water stop, and both ends of the water stop are fixed with positioning steel bars and flat steel.
Tighten both ends of the water stop with flat steel, and weld them with stressed steel bars or positioning steel bars, or use steel hoops in the horizontal direction to ensure the accuracy of their positions. For the vertically arranged water stop, concrete pads with a spacing of 300mm can be bound on the formed steel bars, and the interface parts should be kept flat. In order to ensure the central elevation of the horizontal water stop, the positioning control line should be determined on the template, and the steel bar with water stop ring should be spot-welded on the bottom steel bar to check the elevation. For the vertical direction of the water stop, the verticality of the water stop can be controlled by tying it to the control point at the bottom with a hanging hammer.
In order to fix the water stop, the water stop can be fixed on both sides with square wood, and the outer steel pipe support body and the formwork can be fixed into a whole with fasteners and lead wires.
When pouring concrete and positioning the water stop, we should pay attention to the strength of pouring concrete to avoid piercing the water stop with excessive force. If cracks are found, they should be repaired in time, otherwise, when the joints are deformed and subjected to groundwater pressure, the water stop may lose its deformation ability due to huge external force and break when it reaches the ultimate tensile stress.
Place polystyrene foam board on one side of the formed concrete, fix the foam board on the concrete with pre-embedded galvanized iron wire, and place concrete protection blocks on the stirrups on the other side where the concrete is not poured. ② Install and fix the detachable water stop. In order to install the detachable water stop, the embedded bolts can be fixed on the steel plate in advance and poured into the embedded concrete, which should be vibrated carefully in time to ensure its compactness. The corner of the deformation joint should be made into an arc or 45 angle, which is convenient for installing the detachable water stop. The radius of arc should be determined according to the length of embedded bolts, and the distance between two adjacent bolts does not affect the installation of water stop and water stop splint. In order to prevent corrosion when embedding bolts,
In order to ensure the fixing and accuracy of the water stop, the water stop can be punched with a belt at the bolt position, and the construction and installation should start from complex nodes. The water stop should be laid on the bolt and punched, so as to ensure that the water stop should be installed on the embedded bolt as soon as possible after punching, to prevent the temperature change from affecting the position of the water stop, and then installed on both sides. Slate board or soft metal pad should be used between water stop and splint, and between water stop and embedded steel plate to ensure sealing.
2) Concrete construction. Before concrete pouring, it is necessary to check whether the quality of the water stop meets the requirements, whether the installation position is correct, whether there are sundries in the water stop and the joints, and solve them in time to ensure that the water stop can be well sealed with concrete after concrete pouring. When pouring, concrete should be poured on the bottom plate of deformation joint along the horizontal direction. When the pouring distance is 5cm from the bottom of the water stop, professionals should be sent to tamp and eliminate the air near the water stop. When pouring the water stop, in order to ensure that the water stop is not damaged by vibration, a small vibrating rod can be used to control the vibrating depth of the vibrating rod to ensure the safety of the water stop.
3) Combined therapy. When dealing with the seam of water stop, it must be handled by professionals according to the field situation. When installing the water stop, the interface should be simple, safe and reliable. According to the construction experience, in the field construction, the hot welding method or hot vulcanization method is generally used for docking, so that the quality of water stop lap joint is safe and reliable.
4) Protection of semi-finished products. In order to ensure the construction quality of water stop, the protection of semi-finished products in the construction process can not be ignored, and the welding construction should be as far away from the water stop as possible; It is forbidden to carry steel bars near the water stop. If necessary, you can assign someone to take care of it.
3 Conclusion
The construction of expansion joint water stop is the most easily overlooked place in the construction process. The construction unit should aim at ensuring the safety and quality of the project, analyze the reasons for the rupture of the water stop of the expansion joint, update the technology, properly handle the rupture of the water stop according to the situation, and ensure the quality of the waterproof project.