General concepts on rehabilitation of concrete structures. Objectives.
In reinforced concrete elements, the main goal of protection and repair is to slow down the degradation of concrete and the corrosion of steel reinforcement, restoring their original dimensions and bearing capacities as well as their aesthetic appearance, and extending their durability.
The process of degradation of concrete causes its basic properties to gradually and permanently change, leading to its disintegration. Corrosion of the reinforcement reduces the cross-sectional area and the cohesion of the reinforcement with the concrete, sometimes resulting in the loss of the covering layer.
To maintain and repair concrete structures that have been corroded previously, preventive interventions can also be carried out in advance to extend their durability. An intervention of this type can also be considered remediation when due to the degradation of concrete and corrosion of the reinforcement, the static resistance of concrete elements has been reduced. Therefore, in these cases, strengthening the concrete structure will also be necessary.
Objectives for concrete rehabilitation
Rehabilitating a concrete structure primarily aims to slow down the corrosion processes occurring on the reinforcement’s surface and even prevent these corrosion
processes from occurring. This goal can generally be achieved by:
• Direct anti-corrosion protection of reinforcement bars.
• Re-alkalization of the surroundings of the reinforcement bars or implementation of cathodic protection.
• Providing a sufficiently effective barrier between the reinforcement bar and the surface, which prevents water, oxygen, chlorides, and carbon dioxide from penetrating the reinforcement (concrete carbonation) and sulphur dioxide from entering into the concrete (concrete sulfation).
By doing so, an alkaline environment around the reinforcement will be maintained.
In most cases, combining all these measures is necessary to reliably stop corrosion processes on the reinforcement.
In this context, concrete structure repairs can be classified into four categories based on the requirements for repair and protection:
