Expansion joint waterproofing treatment method

Expansion jointsIt is set up in the process of building construction considering the thermal expansion and contraction caused by the change of temperature, and the building that is too long or too wide will crack due to expansion and contraction, resulting in the destruction of the building. Therefore, during the construction process, the building will be divided into several parts to ensure the expansion and contraction of each section and avoid cracking. There will be a number of problems in the process of expansion joint treatment, such as untimely treatment, expansion joint leakage, thus affecting the quality of the whole project, so expansion joint as a key part of the construction of large buildings, it is of great significance to do a good job in waterproof engineering.

1. Causes of expansion joint leakage

Expansion joint water stop is a very important and easily overlooked problem, once the expansion joint leaks, it is difficult to repair, often bringing huge economic losses. To prevent water leakage in expansion joints, it is often set insideWaterstopThe waterstop belt is divided into metals (copper, stainless steel), rubber (natural rubber, neoprene, EPDM), plastics (PVC, plastic paste, polyvinyl chloride mastic), sealants (polyvinyl chloride, neoprene, butyl, acrylate), composite waterstop materials and many other typesRubber waterstopBecause of its cold resistance, aging resistance, strong tensile and compressive performance, acid and alkali resistance, etc., it is widely used in engineering waterproof and leakage, shock absorption buffering, fastening and sealing, etc. At present, China has stipulated standards for the tensile strength, hardness, tear elongation and other aspects of the performance of rubber waterstops, and in the construction because the waterstop is a key link in the quality of expansion joints, and it is extremely difficult to maintain once there is a quality problem, therefore, the construction quality of the waterstop is the impact of the entire expansion joint and even the construction quality of the entire project.

2. Rubber waterstop waterstop mechanism and installation

2.1 Water stop mechanism

Rubber waterstop is used to its high elastic performance, under various loads will produce elastic deformation and volume expansion will occur after encountering water, so it can play a strong sealing role, which can not only prevent water from outside the building from entering the inside of the building, but also prevent the water from inside the building from seeping into the outside world, and the waterstop can also play a role in shock absorption and buffering.

2.2 Installation of embedded rubber waterstop

Before tying the steel bars, the expansion joint positioning line should be popped up on the upper or lower layer of concrete to determine the expansion joint position; After the steel bar is tied, the waterstop is placed, and the two ends of the waterstop are fixed with positioning steel bars and flat steel, and the two ends of the waterstop are tightened with flat steel and welded with structural steel bars or positioning steel bars; The flat steel is fixed with bolts at a certain distance to ensure that the hollow ring in the middle of the waterstop coincides with the center of the deformation joint, and the two ends of the waterstop should be slightly raised to form a horizontal angle of 15°~30° with the hollow ring in the middle, so as to facilitate the discharge of internal air when pouring concrete. The vertically set waterstop should be fixed with a certain spacing of concrete spacers on the shaped steel bar, and its interface should be kept flat. In order to ensure the center elevation of the horizontal rubber waterstop, the control line should be popped up on the formwork, and the steel bar with a waterstop ring should be spot-welded at the bottom plate reinforcement to check the elevation. Generally, the method of hanging the line from the bottom control line position is used to control the verticality of the vertical rubber waterstop.

2.3 Removable rubber waterstop installation

In order to facilitate the installation of the removable waterstop, it is necessary to install the embedded bolts in advance, and the embedded bolts should be fixed on the steel plate of the waterstop plate with steel plates embedded in advance, and poured and embedded inside the concrete, and the part of the concrete should be carefully vibrated to ensure its compactness; The corner part of the deformation joint should be made into an arc or a 45° angle, and the arc radius should be determined according to the length of the embedded bolt, and the distance between the two adjacent bolt heads should not affect the installation of the waterstop and the waterstop cleat. When embedding the bolt, in order to prevent it from being corroded, butter or PVC sleeve should be added to the bolt; The fixation of the waterstop should be based on the actual position of the bolts on site, and the waterstop should not be pulled hard during the installation of the waterstop.

2.4 Concrete pouring

Before pouring concrete, the waterstop and debris in the joints should be cleaned, and the surface area of the waterstop should be absorbed before pouring, so as to ensure that the waterstop and the concrete are closely integrated. When pouring the horizontal deformation joint (bottom plate) concrete, there must be a special person responsible for tamping and exhausting near the waterstop, and the first layer of concrete should be poured to make the pouring layer slightly higher than the waterstop, so that the concrete can be vibrated and compacted at one time, and finally use a round wooden stick to tamp the upper part of the waterstop point by point to discharge the bubbles under the waterstop. For the vertical deformation joints of the pool wall, the concrete should be poured in layers on both sides at the same time, and attention should be paid to adjusting the gradation of aggregates to ensure the strength and compactness of concrete.

3. Analysis of the causes of waterstop fracture

3.1 Concrete shrinkage

Most of the buildings with expansion joints are ultra-long or ultra-wide structures, and the construction process is long, and the construction period will be relatively long when the construction joint is concreted at the right time, so it is easy to cause the waterstop to break due to the shrinkage of the concrete after the construction is completed.

3.2 Ambient temperature difference

Generally, buildings with construction joints usually wait until a certain period of time to make the structure on both sides of the expansion joint basically stable, that is, when the expansion and contraction amount is negligible, the concrete pouring of the construction joint will be completed, so the construction period will be relatively long, during this period, the temperature of the environment will also change with the seasons, which will lead to the expansion and contraction of concrete due to the large temperature change and the expansion and contraction will increase, if it exceeds the bearing limit of the rubber waterstop, it will lead to the fracture of the weak part of the rubber waterstop.

3.3 Construction reasons

If the quality control of the waterstop installation is not good during the construction process, it will cause its contact surface to easily detach or produce pores, and the existence of pores makes the connection between the waterstop and the concrete not tight or even detached due to the presence of bubbles, or the large particle size aggregate in the concrete enters the bottom of the waterstop, and when the upper concrete is poured, the waterstop breaks due to the action of the aggregate at the bottom of the waterstop. Because the concrete on both sides of the horizontal expansion joint is not poured at the same time, the post-pouring part must wait for the strength of the poured part of the concrete to meet certain requirements before it can be carried out, therefore, the exposed time of the rubber waterstop is longer, during the construction period, it is necessary to carry out steel bar binding, formwork support and other process construction, involving more materials, if the construction is not careful, it will cause the waterstop to be pierced and even fractured.

4. Solution

4.1Chemical grouting method

For the breakage of the expansion joint waterstop of the bottom plate, chemical grouting plus the removable waterstop method can be used to compensate. Because the chemical grouting material has good adhesion performance with concrete, it has good elasticity and water expansion after it forms a solid. Before grouting, the polystyrene board, cracked waterstop and other debris in the original expansion joint should be manually removed with a steel file, and then the concrete surface within a width of 500mm should be used to make the surface clean, flat and smooth. The seam and other debris in the seam can be cleaned, and high-pressure pouring can be carried out through the grouting pipe in stages according to the actual situation, and after pouring, anti-corrosion wooden strips are added to the surface of the expansion joint, and then top-pressed steel plates are added; For the wall expansion joint, it is necessary to add reinforced concrete baffles and caulking fillers on the outside, and then use chemical grouting to seal the expansion joints about 1 meter above the wall and make the chemical grouting overlap with the rubber waterstop to form a water hydrant; After the construction is completed, the observation of the width of the expansion joint with temperature and the overall deformation of the basement structure should be organized to facilitate the control of the quality of remediation.

4.2Stuffing method

The same method should be used to clean up before plugging. Then use an electric drill to drill holes on both sides of the expansion joint at a certain distance and embed the expansion bolts. The specifications of expansion bolts should be determined according to the actual uneven settlement difference, the position of the bolts must be accurate, and the embedding must be stable. After that, the processed asphalt hemp wire is stuffed into the expansion joint with a hand hammer for preliminary water stop, and the filling depth of the asphalt hemp wire should be controlled during the construction to ensure the water stop effect and save the amount of expanded rubber. After the initial water stop of the asphalt hemp wire, in order to achieve better results, it is best to use expanded rubber plugs to fill the gaps that the asphalt hemp wire cannot fill, and finally the surface of the expanded rubber should be level with the concrete surface, and ensure that the gaps must be filled tightly; After that, the concrete surface should be cleaned again, and the flatness of the expanded rubber surface should be tested, and the rubber plate or steel plate should be installed after meeting the requirements, and the length of the plate should be the same as the length of the gap, and the drilling position and spacing of the plate should be the same as the drilling and position of the expansion bolt.

The expansion joint waterstop is a key part of the construction quality of large buildings, and it is also a weak link in construction, so it should be attached great importance in the construction process, and a technical public relations team should be set up to ensure that the construction is carried out according to the requirements to ensure the quality of the project.