Patch repair: why common repair strategies can cause further problems

This session focuses on what is known as the incipient anode, or halo effect, in patch repairs, presented in a friendly and easy-to-understand manner. The presentation begins by covering the basics of corrosion (rust) of steel in concrete, including how corroding steel may be protecting the surrounding steel from corrosion. It then moves on to discuss patch repairs and how removing the concrete surrounding the corroding steel and replacing it with fresh patch repair material can make the steel in the patch passive, but can also adversely affect the steel surrounding the patch, potentially leading to additional cracking and spalling around the repair within as little as 3–5 years, leading to more repairs, which each can cause more corrosion. 

Following the discussion of patch repair issues, the session reviews available treatment options and compares the two most common solutions on the market. Although these solutions appear similar, one has performance limitations that can ultimately lead to failure.