Carbonation and chlorides attacks induce the corrosion of rebars in concrete. Fig 1 shows the rebars corrosion, cracking, and spalling of concrete cover. The repair methods commonly include mortars (cementitious & resin) and coatings (cementitious & polymer modified). What are other emerging repair trends of concrete corrosion deterioration?
There are many ways to repair such structures. These can be done in two steps. One is preparation of surface after removing loose materials and dust and then treatment.
FRP applications and micro-concreting are done depending upon the extent of damage and level of strengthening required.
You can find summary for different techniques in the following research
Conference Paper State-of-the Art Review: Strengthening of Reinforced Concret...
There are 2 different ways of a successful long-time protection of concretes:
A. Pre-treatment of rebar iron by phosphatizing (Zn-, Mn-, Ca-phosphates etc.)
B. Repair of damaged concrete structures by special repair mortars with extreme low gas and liquid permeabilities for CO2, H2O as well as chloride-containing solutions. This may be achieved by utilizing higher amounts/additions of Nanosilica dispersions (5-10% BWOC). Even brush applications of nanosilica dispersions on poured fresh concrete surfaces (> 1 - 2 d) may help and protect the upper surfaces.
You brush off the corrosive particles and remove the concrete cracks careful. Provide iron bars round weak bars but make sure the formwork for fresh concrete to be casted is watertight but if the corrosion is not severe you can brush the surface and provide a wire mesh on the surface and re-plaster it with rich mortar mix
Except the different techniques mentioned above, other two ways to protect against corrosion is as follows:
1. Surface application of inhibitors: The inhibitors exhibit high mobility, which help to reach sufficient amount to rebar level in short period of time to give higher resistance to corrosion.
2. Cathodic protection: Sacrificial anode system and impressed current system are two emerging technique used now days to protect rebar corrosion. The basic mechanism of the method is reverse the flow of current in steel-concrete interface by introducing external anode. That means the steel rebar act as cathode and dissolution takes place at anode which is placed externally.
MOHAPATRAs techniques recommended are very good ideas, BUT...
1 Sorry, adsorptive corrosion inhibitors will not do their work as you like:
- Applications of alkaline vapor phase inhibitors will give a temporary
protection only, but have shown nearly NO permanent effect on rebar
protection in concretes! ...and eco-toxicity?
- Probably typical acid inhibitors may work at reasonable high concentrations
and have to be incorporated into the whole fresh concrete mix (expensive)!
But the pH will be far too high and the pore fluids are not sufficient/enough for
the necessary mobility of the inhibitor molecules,
and when the pH has changed to acidic, it's far too late already for the rebar
and the whole construction!
2. For sure, good cathodic protection systems will work, but the complete rebar
construction has to be connected/welded to a conductive grid. Who will do and
pay for and approve? (Economics?)
In total continuous cathodic protection over the life span of a construction will
be very expensive (golden cage ?)
It has been a pleasure to appreciate this exchange, all the criteria have been excellent and correct. I would add only a modest criterion, all the techniques that are chosen must be in correspondence with the cost-benefit and of course depending on the importance of the work that must be repaired and the level of structural damage
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