Two Remedies for Rubber Waterstop Breakage in Expansion Joints

Rubber waterstop for expansion joints

Waterstop is a key factor that affects the engineering quality of expansion joints, deformation joints and construction joints and it is extremely difficult to repair once it has quality problems. Therefore, the construction quality of waterstop is a key link that affects the quality of the whole project.

In this article, we analyzed the possible reasons for rubber waterstop breakage in expansion joints and bring forward targeted remedial measures to ensure the overall quality of the project.

According to our experience and research, we found that the rubber waterstop breakage may arise from the following reasons:

• Large environmental temperature difference

  Due to the long construction period of large-scale structural buildings, it takes a long time to complete the expansion joint construction. During this period, the environment temperature difference changes greatly and the linear expansion coefficient of the concrete varies accordingly when it expands and contracts freely. As a result, the concrete produces a large liner expansion. However, the rubber waterstop fails to adapt to such deformation and cause stress concentration, thereby leading to the weak part breakage.

• Improper construction

  In the construction process, if the rubber waterstop is not installed properly, the contact surface between the concrete and the rubber waterstop will have air voids and make the rubber waterstop cannot tightly connected with the concrete and even peel off from the concrete due to air voids. In addition, it will also lead to large gravels in the concrete entering the bottom of the rubber waterstop and cause rubber waterstop breakage due to the action of the gravels beneath when pouring the upper layer of concrete.

  The concrete on both sides of the horizontal expansion joint is not poured at the same time. The second pouring can only be carried out when the concrete strength of the previous-casting part meets relevant requirements. As a result, the rubber waterstop exposure lasts a long period. During the construction, steel bar binding and formwork support are performed, which requires a variety of materials. If these materials are not handled properly, it may pierce through the rubber waterstop and even causes rubber waterstop breakage.

• Concrete expansion joint shrinkage

  Building with expansion joints generally requires a long construction period. The concrete gradually shrinks as time changes after pouring. In the later stage, if the concrete shrinkage exceeds the tensile stress of the rubber waterstop, it will lead to stress concentration and cause the weak part breakage.

All reasons aforesaid may cause the rubber waterstop breakage. Here we bring forward two remedies to solve this problem.

• Chemical grouting method

  It is mainly targeted at solving the problem of concrete expansion joint shrinkage. The chemical grouting material has good adhesion properties with concrete, and has good elasticity and hydro-expansibility when it becomes solid. We can use chemical grouting method together with inserted rubber waterstop for rubber waterstop breakage remedy.

  Standard operating procedures are as shown below:

  1. Before grouting, remove the polyamine board, cracked rubber waterstop and other debris in the original expansion joint with a steel file;
  2. Wash the concrete surface to be treated within a wide range of 500 mm to make the surface clean, flat, smooth and free from debris;
  3. Conduct high-pressure pouring via the grouting pipe by several times as the case may be;
  4. Add anti-corrosion wood strips to the expansion joint surface after pouring, and then jacking steel plates;
  5. For wall expansion joints, add reinforced concrete baffles and caulking fillers to the outer surface. And then use chemical grouting materials to seal the expansion joints about 1 meter at the top of the wall, and connect these materials with the rubber waterstop;
  6. When the construction is completed, observe the change of the expansion joint width with the temperature and the overall change of the building to facilitate the quality control of remediation.

• Stuffing method

  Stuffing method is mainly targeted at solving the problem of the rubber waterstop breakage arising from improper construction. Featured by great hydrophobicity, high elasticity and not easy to be extruded, asphalt hemp fiber can effectively meet the waterproof performance of buildings.

  Standard operating procedures are as shown below:

  1. Remove the cracked rubber waterstop and other debris in the original expansion joint with a steel file;
  2. Wash the concrete surface to be treated within a wide range of 500 mm to make the surface clean, flat, smooth and free from debris;
  3. Drill holes with an electric drill and pre-embed expansion bolts on both sides of the expansion joint at certain intervals. The specifications of the expansion bolt shall be determined based on the actual uneven settlement difference. The expansion bolt must be positioned accurately, and pre-embedded firmly;
  4. Stuff the processed asphalt hemp fibers into the expansion joint with a hammer for preliminary water sealing. During the construction, the depth of the stuffed asphalt hemp fibers shall be controlled to ensure an excellent waterproof effect;
  5. Expansion rubber is preferred to fill the gaps that are not fully filled up with asphalt hemp fibers to achieve a better waterproof effect. The expansion rubber surface shall be level with the concrete surface, and the gap must be filled tightly;
  6. Finally, wash the concrete surface and test the flatness of the expansion rubber surface;
  7. In order to meet the waterproof requirements, rubber plates or steel plates can be installed on the outside or at the bottom of the expansion joint. The length of the plate used shall be the same as that of the joint. The drilling position and spacing of the plate shall be the same as those of the expansion bolt.

Waterstop is a key part of the construction quality of large buildings and a weak link of the construction. Therefore, great importance must be attached to make sure that all construction requirements are met to ensure the quality of the project. Proper measures must be taken to deal with the breakage of rubber waterstop and provide a strong guarantee to ensure the service life of the project.