The best way to correct splinters is to use a high-pressure sprayer to remove any surface rust that may be present. A special protective coating containing anticorrosive agents is then applied to the exposed metal to prevent further damage. After this material has set, new mortar can be applied to fill the space and, in fact, cover the exposed reinforcing bar. Because the prestressed strand is attached, only the exposed and damaged section is re-stressed after repairs.
In a relatively short space of time, the surface of the fresh concrete will have reacted with the CO2 in the air. However, the concrete removal process must continue to clear a gap of maximum aggregate dimension plus 6 mm behind the steel bars when they must lose rust, corrosion, or not adhere properly to the concrete. The initial high CP current completely passives the steel reinforcement, which causes chlorides to move away from the bars and restores an alkaline environment in the concrete. It may be necessary to prop up the section being repaired and the adjacent spans up to several compartments apart before removing or re-tensioning the unattached pre-tensioned cords.
It is the result of water penetration; water enters through the cracks in the concrete and comes into contact with the metal, which, over time, causes oxidation of the reinforced steel and corrosion from the inside out of both the rebar and the concrete. Chlorides, usually from splashes by the sea or places blown by the wind, will migrate to porous concrete over time. Sometimes rebar can slip out of position when concrete is poured and therefore you don't get proper coverage. Once the CP is installed, ongoing corrosion can be controlled in the long term, and future chips and deterioration are eliminated even in concrete severely contaminated with chlorides or carbonation.
The high pH (alkalinity) of concrete forms a passive film on the surface of reinforcing steel rods that prevents or minimizes corrosion. The repaired area should be protected with a polyethylene sheet against drying out due to wind or rapid evaporation. Unbonded high strength wires may need to be de-tensioned prior to repair and re-tensioned after repair to restore the initial structural integrity of the member. The repair procedure requires replacing the damaged section with the new strand section connected to the existing ends of the undamaged strands.
First, the concrete will be weaker, and secondly, shrinkage cracks can be larger and allow moisture to reach the reinforcing bar. If the reinforcing bars are only partially exposed after removing all of the defective concrete, it may not be necessary to remove additional concrete to expose the entire circumference of the reinforcement. Fresh concrete shrinks as water dissipates from the concrete, causing cracking, and if too much water is added, the concrete weakens.
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