To effectively repair cracks in concrete, a process called grouting is used. This process involves filling and repairing the cracks to restore the integrity of the structure. However, it is important to follow a step-by-step grouting procedure to ensure that the repair is effective.
The first step in the grouting procedure is to identify the cracks that need to be repaired. This involves inspecting the concrete surface and determining the location and extent of the cracks. Once the cracks have been identified, they need to be cleaned thoroughly to remove any dirt, debris, or loose concrete particles that could interfere with the repair process.
The next step is to prepare the grout mixture, which involves mixing cement, water, and any other additives as required. The grout mixture needs to be mixed to the right consistency to ensure that it can be easily injected into the cracks and fill them completely.
Once the grout mixture has been prepared, it can be injected into the cracks using a grout injection pump. This ensures that the grout is forced deep into the cracks, filling them completely and effectively repairing them. After the injection, the surface should be cleaned and any excess grout should be removed.
Finally, the repaired area should be allowed to cure for a sufficient period of time to ensure that the grout has fully set and hardened. This will ensure that the repaired area is strong and durable, and that the cracks will not reappear in the future. By following this step-by-step grouting procedure, it is possible to effectively repair cracks in concrete and restore the integrity of the structure.
Grouting Procedure for Repair of Cracks in Concrete Structures:
Grouting is a common method used for repairing concrete cracks in structures. The procedure involves drilling holes along the cracks and in hollow spots. If there are several cracks, the holes can be drilled in a staggered manner at 500 to 750mm spacing in both directions to adequately cover the proposed grouted area. The spacing of the holes can be adjusted as per site conditions.
G.I. pieces or PVC nozzles with one end threaded are fixed in the holes using rich cement mortar. After fixing, all the cracks and annular space around G.I. pipes are sealed with the same mortar. In addition, all the cracks are cut open to a ‘V’ shaped groove, cleaned, and then sealed with rich cement mortar.
Before the actual grouting, all the grout holes should be sluiced with water using the same equipment, a day before grouting, to saturate the masonry. All holes are first plugged with wooden plugs or locked in the case of PVC nozzles. The bottommost plug and the two adjacent plugs are removed, and water is injected into the bottommost hole under pressure. When the clear water comes out through the adjacent holes, the injection of water is stopped, and the plugs in the bottommost hole and the one immediately above are restored. This process is repeated with other holes till all the holes are covered.
On the day of grouting, all the plugs are removed to drain out excess water and restored before commencing grouting. The same sequence as described above is adopted for injecting the cement grout also. The grout is kept fully stirred and agitated under pressure throughout the grouting. The grouting is carried out till refusal and/or till grout starts flowing from the adjacent hole. A proper record of the quantity of grout injected into every hole should be maintained.
After grouting, curing should be done for 14 days. Tell tales are provided for checking the effectiveness of grouting. Only such quantities of material for preparing grout should be used as can be used within 15 minutes of its mixing. Grouting equipment must be cleaned thoroughly after use.
Fig: Grouting Procedure for Concrete Cracks Repair
Precautions during Grouting of Cracks in Concrete :
During grouting operations near railway tracks, speed restrictions of stop-dead and proceed at 10 kmph should be enforced at the work site for a period of 24 hours. Afterward, the restriction may be eased to non-stop 30 kmph for another 2-3 days. However, these speed restrictions are only general guidelines, and the appropriate speed limit at each individual site should be determined.
All grouting equipment, including slurry and mixing drums, pipes, and nozzles, should be thoroughly washed immediately after grouting to prevent set cement from damaging the equipment.
After the grouting work is completed, the structure should be inspected thoroughly and kept under observation for a period of 6 to 12 months to assess its behavior after grouting. In some cases, load tests may be conducted on selected arch masonry bridges that have been grouted to strengthen the structure, to ensure that the grouting has reduced the deflection of the crown and spread at the springing to within acceptable limits.