Repairing concrete structure passes through various stages. Selecting the correct repair method will depend on completing the previous steps, such as determining the cause of concrete damage, evaluate the extent of the damage, and assess the need for repair. The completion of these steps will define the type of conditions the repair must resist, the available repair construction time period, and when repairs must be accomplished. The data collected from performing these steps will help in selecting which of the 15 standard methods is suitable and durable for repairing the damaged concrete structure.
In general, the old concrete surface should be prepared before beginning with the repairing process. It is essential to remove all unsound concrete before applying the repairing. Improper preparing of damaged concrete structure will result in unsatisfactory repair with low durability. The first step in preparing the old concrete surface is the saw cutting of repairing area perimeters. The saw cut depth will range from 25-40 mm. The saw cutting of the repairing area perimeters aims to produce a retaining boundary to compact the repairing materials. Usually, the boundary of repairing area will be susceptible to shrinkage, bond failure, and deterioration. The saw cut in the concrete surface should be perpendicular to a concrete surface or tilted inward by 2 to 3 degrees to provide a retaining surface that will interlock the repairing materials into the area. Tilting the saw cut by more than 3 degrees can produce a weak top corner. The figure no:2 showing correct saw cut patterns. Saw cutting concrete at an acute angle, as shown in figure no:2, is incorrect, and it will complicate the compaction of repairing of material, which may impair the repairing of concrete.
Deteriorated concrete should be removed entirely to ensure the durable repairing of the damaged concrete structure. The removing of deteriorated concrete can be performed by high-pressure hydro blasting or hydro demolition. The using of this method will ensure the removal of unsound concrete while leaving the sound concrete on the place. Also, this method will not leave any microfracture surfaces on old concrete. Impact concrete removal techniques such as jackhammer and bush-hammering can also be used to remove deteriorated concrete surfaces. The using of this method can have some disadvantages, such as affecting the bond of reinforcement with surrounding concrete and surface micro fracturing. Pointed hammer bits, which are more likely to break the concrete cleanly rather than to pulverize it, should be used to reduce the occurrence of surface micro fracturing.
Reinforcement steel should also be prepared before applying the repairing materials. all rust, scaling, and corrosion must be removed by sandblasting, wire brushing, or high-water pressure. The preparing of reinforcement steel will ensure a strong bond between repairing material and the reinforcement. It is not necessary to clean the steel to white condition. The purpose of reinforcement steel preparation is to remove loose rust and debris. If the corrosion reduces the cross-section of reinforcement steel by more than 75% of the original diameter. The bar should be removed and replaced.
Once the repairing area is ready, we can apply the repair method. There are different 15 standard concrete methods such as surface grinding, Portland Cement Mortar, Dry Pack and Epoxy-Bonded Dry, aced Aggregate Concrete, shotcrete, replacement of concrete, Epoxy-Bonded Epoxy Mortar, polymer concrete, Thin Polymer Concrete Overlay, resin injection, High Molecular Weight Methacrylic Sealing Compound, Polymer Surface Impregnation, Silica Fume Concrete, and Alkyl-Alkoxy Siloxane Sealing Compound. Each of these materials has uniquely different requirements for a successful application. Proper curing of repairing area will ensure a durable concrete. Almost all repairing method requires appropriate curing. Improper curing can reduce the service life of the repairing methods.