First upon holes are drilled along the crack in this structure and in and around hollow spots.
If there are several cracks the holes can be drilled in a staggered manner at 500 mm to 750 mm spacing in both directions covering adequately the area proposed to be grouted.
The holes spacing can be changed as per the requirement and the site conditions.
The Galvanized Iron pieces ( 12 to 20 mm diameter X 200 mm) with one end threaded or PVC nozzles are fixed in the holes with rich cement mortar.
All the cracks and annular space around G.I. pipes are filled with rich cement mortar.
All the cracks are cut open to a ‘V’ shaped groove, cleaned, and sealed with rich cement mortar.
All the ground holes will be closed with water using the same equipment a day before grouting.
All holes are first plugged with proper wooden logs are locked in the case of PVC nozzles. The bottom-most plug and the two adjacent plugs are removed and cement water injected in the bottom-most hole under pressure.
When the cement water comes out through the adjacent holds the injection of cement mortar is stopped and the plugs in the bottommost hole and the one immediately above are restored.
The process of grouting of concrete cracks is repeated with other holes till all the holes are covered properly.
It is important that on the day of routing all the flags should be removed in order to drain out the excess amount of cement water and restore before starting the process of grouting.
The grout should be kept fully stirred under pressure throughout the process of Grouting. The grouting is carried out till refusal and till crowd starts flowing from the hole present at its adjacent.
A proper record of the quantity of grout injected into each hole should be maintained.
After the process of grouting, it is very necessary that proper curing should be done for or at least 14 days. All the equipment which are used in the process of grouting should be clean thoroughly after its use.
Precautions Should Be Taken During the Process of Grouting of Cracks in Concrete
In the case of the arch masonry of the bridges, the grouting is done to strengthen the structure. Some load tests may be carried out in selected structures to satisfy that grouting has helped to reduce the deflection of the crown and spread at the springing to within permissible limit.
After completing the grouting work, all the equipment which are used in grouting including the slurry and mixing drums, nozzles should be thoroughly washed otherwise cement will get set.
After the grouting work is completed it should be inspected thoroughly by the expert and should be kept under observation for a period of 6 to 12 months for its behavior after grouting.
Shotcreting is a concrete repair method. The first one removes the Plaster and finishes all around the distressed concrete surface.
Remove concrete all around the reinforcement in order to get an average 25mm air gap.
Put the additional information wherever the reinforcement diameter has been reduced by more than 15 to 20%.
Fix shear key bars of appropriate diameter at a specified spacing in both directions over the surface to be covered with repair materials.
Apply appropriate passivating and Bond Court over the reinforcement and prepared RCC surface.
Shotcreting should be done with a 6mm thick finishing coat. It is also necessary to do wet curing over the finished surface of the shotcrete for a minimum period of 7 days.
Use a small sledgehammer and chisel to undercut the edges of the crack.
Clean the area in and around the crack with a wire brush and broom.
Mix vinyl patching compound as directed by the manufacturer and trowel the compound into the cracks.
Smooth the mixture with a trowel.
When the patch has set (see manufacturer's instructions for the patch compound you're using), smooth or brush the surface to match the surrounding area.
Use a small sledgehammer and chisel to undercut the edges of the crack. Undercutting the crack makes it wider at the base than at the surface, providing a mechanical method of keying the concrete patch in place for a more secure and permanent repair. For more information, see How to Break Up Concrete.
Clean the area in and around the crack with a wire brush and broom. Wash the area with a stream of water.
Mix vinyl patching compound as directed by the manufacturer and trowel the compound into the cracks. Tamp the mixture to remove air pockets with a tamper. If you use patching mortar instead of vinyl concrete crack sealer, either mix it with a bonding agent instead of water or coat the edges of the surface to be repaired with a bonding agent.
Smooth the mixture with a trowel.
When the patch has set (see manufacturer's instructions for the patch compound you're using), smooth or brush the surface to match the surrounding area.