The strength and stability of buildings, bridges, water retention structures, sewage treatment plants, docks, and other structures are often dependent on concrete. Repair methods should be designed to ensure the expected or desired remaining service life of the structure. It is important to distinguish between repairs that are intended to stop deterioration altogether and those that are meant to simply slow down the deterioration process for a limited period of time. This article will discuss repair methods relevant to damaged concrete structures, focusing on design methods, application principles, and limitations.
The scope of relevant repair methods includes the application of penetrating corrosion inhibitors and surface coatings, temporary electrochemical techniques, cathodic protection systems, bonded overlays (patch repairs), and crack injection. Additionally, the article will provide an introduction to deterioration mechanisms, condition assessment principles, non-destructive testing of concrete structures, and standards for concrete repair. Gunite is a mechanically applied material consisting of cement, aggregates, and water. Cement and sand are dosed and mixed in the usual way and transported through a hose with the aid of compressed air.
A separate pipe carries the water under pressure and the mixture of water-cement aggregates is passed and mixed intimately in a special collector before being projected at high speed to the surface being repaired. The costs associated with repairing deteriorating concrete structures can be substantial; however, costs resulting from poorly designed or executed repairs may be even higher. To address this issue, various types of retrofitting methods have been developed for the repair and rehabilitation of faults in concrete structures. These methods include increased coverage with additional mortar or concrete; replacement of contaminated or carbonated concrete; electrochemical recalination of carbonated concrete; diffusion carbonated concrete; and carbon wrap for columns.
The carbon wrap for columns is an ideal strengthening method for plates while high-strength, lightweight, and earthquake-resistant structures are required. Confinement is one of the rapid repair techniques that is popular and has proven to be efficient in restoring the original capabilities of damaged concrete. This technique blocks the pores of concrete to reduce the absorption of water and salts or form an impermeable layer that prevents the passage of such materials. A low viscosity liquid monomer or prepolymer is then partially or wholly impregnated or diffused into the pore system of hardened cement composites or cement concrete before being polymerized using radiation or by application of heat or by chemical initiation.
Historically, polymer concrete has not been widely adopted due to the high costs and difficulty associated with traditional manufacturing techniques. However, recent advances have led to significant reductions in costs which means that the use of polymer concrete is gradually becoming more widespread. The adhesive properties of polymer concrete allow for the repair of both polymeric and conventional cement-based concretes. Autogenous curing is another natural crack repair process that can occur in concrete in the presence of moisture and absence of tensile stress. The repair and rehabilitation of existing damaged concrete structures has become one of the most important construction activities worldwide.
Depending on the condition and location of cracks, it must be cleaned of foreign matter before loose or damaged concrete can be removed. Fibers such as steel fibers, glass fibers, synthetic fibers, natural fibers, etc., can be added to impart variable properties to concrete. The character of fiber-reinforced concrete changes with concretes, fiber materials, geometries, distribution, orientation, and varying densities. If internal tensile stresses are greater than the tensile strength of concrete, a crack may develop. Stitching is a rehabilitation method used in cracks to maintain interlocking aggregates and provide additional reinforcement to minimize relative movement in slabs.