Concrete Crack Repair:
It is commonly observed that concrete structure face cracking problem during its life period. This crack must be given serious and careful attention and repair on right time. Repairing cracked concrete involves a lot of time and cost constraints. There are several methods of concrete crack repair. Choosing the appropriate method of concrete crack repair can help you save a lot of time, money and energy and can give long-lasting results. It is essential to know the type and nature of cracks that have appeared in the building to be able to select the most suitable and cost-effective method of repair. It is also important to know the cause of cracks so that it can be corrected to keep the cracks from recurring.
1) Epoxy Injections:
Epoxy injection method of concrete crack repair may be used to bond the cracks having greater than or equal to 0.05mm opening. This method is not suitable for crack is active and if the cracks are large in number, or when the water leakage cannot be controlled.
In this method, the cracks on exposed concrete surfaces are sealed by injecting epoxy under the concrete crack. But, it is essential to find and fix the major cause of cracks before injecting the epoxy into the cracks otherwise the cracks will keep on emerging again and again. Problems such as leakages and silt contamination damage the efficiency of epoxy, therefore it is recommended to fix these issues before injecting the epoxy to make it last longer. Epoxy injection method of crack repairing requires a lot of discipline and skillful execution so you need to be sure that the person executing the repairs knows his work.
Epoxy resin loses strength when exposed to fire or sustained elevated temperatures and fireproofing protection is required for such structural repairs. MOre
Read More: WHICH CEMENT IS BEST FOR HOUSE CONSTRUCTION
Concrete Crack Repair
2) Routing and Sealing:
Routing and sealing the cracks is a much more common and a much simpler method to repair cracks. That said, it can be only used in cases where only remedial crack repairing is required and structural repairs are not needed. Routing and sealing of cracks in concrete can be used for inactive cracks not involving the restoration of tensile strength. Under this method, the crack is enlarged along its exposed face and V-shaped groove is formed up to a minimum width of 6 mm and a depth of 6 to 25 mm. This V-shaped groove is filled and sealed with suitable material.
It should be taken care of the width to depth aspect ratio when sealing the joint so that there is enough room left for the movement.
While repairing roadway pavements, pouring hot tar within the cracks is a simple and inexpensive method. Be careful when using hot joint sealants and make sure that they bond with the concrete and do not melt and flow under operating conditions.
The material used as the sealant can be of any material that can balance cyclic expansion and contraction and which does not become brittle with time, including epoxies, urethanes, silicones, polysulfides, asphaltic materials, or polymer mortars.
Cement grouts are not to be used due to the chances of future cracking.
3) Stitching the Cracks:
It is an easiest and long-lasting method of repairing concrete cracks. In this method, a number of the hole drilled along the crack surface and stitched with metallic wire. This metallic U-shaped wire is then passed through holes and anchored strongly in the holes with grout or an epoxy-based system.
4) Drilling and Plugging
When it is required to repair a vertical crack in the concrete that runs in straight lines, this is a good method for its cost-effective and less time-consuming. In this method, holes are drilled vertically in the cracks and a key is formed by passing down a grout. The grout key drilled in concrete helps in preventing leakages.
Above four methods is a major method of concrete crack repair. Concrete crack can be repaired by Gravity Filling, dry packing, overlay and surface treatments, etc. selection of the method of repair depends on nature of cracks and whether a crack requires remedial or structural repair.
Concrete Crack Repair
5) Grouting Method of Crack Repair:
i) Portland cements grouting:
In case of gravity dam and concrete wall large-sized crack formed. They can be repaired by filling with Portland cement grout. This grouting method is effective in stopping water leaks, but it will not structurally bond cracked sections.
The procedure consists of,
- Cleaning the concrete along the crack.
- Installing built-up seats (grout mesh) at suitable intervals (to provide a pressure-tight connection with the injection apparatus).
- Sealing the crack between the seats with cement paint, sealant, or grout;
- Flushing the crack to clean it and test the seal; and then grouting the whole area.
In this method, mixtures of grout may contain cement and water or cement plus sand and water, depending on the width of the crack.
However, the water to cement ratio should be kept as low as practical to minimize shrinkage and to maximize the strength. Other admixtures or water reducer may be used to improve the properties of the grout.
For this treatment a manual injection gun may be used in case of small volume crack filling and for larger volumes, a pump should be used. The good pressure should be maintained for several minutes after the group is filled over a surface to ensure good penetration.
ii) Dry packing:
In this method, the hand placement of a low water content mortar is done by tamping or ramming of the mortar into place to make intimate contact between the mortar and the existing concrete.
As we use the low water-cement ratio for grout mix, there are chances little shrinkage, and the patch remains tight and can have good quality concerning durability, strength, and water tightness.
Dry pack method can use for the small-sized crack of inactive nature. Dry pack method is not suitable for filling or repairing active cracks.
Before applying grout by dry pack method the slot of 25mm x 25mm must open to a concrete surface. The slot opening should be such that so that the base width is slightly greater than the surface width.
The mortar should prepare before 30 min after mixing water to minimize chances of shrinkage and then should be remixed before use. This mortar should be placed in layers about 3/8 in. (10 mm) thick.
Each layer should properly be compacted by blunt stick or hammer, and the old layer should be scratched to facilitate bonding with the next layer.
The repaired surface should be cured by using either water or a curing compound.