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Surface Preparation and Protective Treatments - Lesson Summary

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Durable repair is needed and this can be achieved through surface preparation of concrete and steel. It is worthy of note that:

Regular shaped repairs must be privileged for they last longer than irregular ones
Undercutting beyond depth of rebar is crucial to ensuring strong bond between steel and repair
Corroded steel must be cleaned properly to achieve strong bond with repair material
Specific tools can ensure better quality work with minimal human resources and turn around time

There are various treatments available to protect the steel in concrete from corrosion, namely alkaline slurry protection, cathodic prevention and protection, and electrical insulation.
 
In the alkaline slurry protection, the alkaline slurry that is applied to the rebar provides alkaline environment and protects the steel.
 
Cathodic prevention and protection includes three types:

Zinc applied to bar surface sacrifices itself to protect the steel
Zinc applied to concrete surface sacrifices itself to protect the steel
A sacrificial anode connected to the bar changes the flow of electrical current to protect the steel bar

 
Alkaline slurry coating is advised and should be done on a clean rebar surface, but adequate precautions should be taken to prevent disbondment.
 
Other protection methods include:

Impressed Current Cathodic protection (ICCP)
Electrochemical Re-alkalization (ERA), and
Electrochemical Chloride Protection (ECE).

 
The various methods of placing the repair materials include:

Trowel application;
Drying packing
Form and cast-in-place
Form and pump
Preplaced aggregate
Dry-mix shotcrete
Wet-mix shotcrete

 
There are three types of curing:

Maintaining the presence of mixing water (during the early hardening period)
Reducing the loss of water (i.e., evaporation) from the surface of concrete (throughout the hardening period)
Supplying external heat and moisture