Expert: Bruce E. Johnson - 3/6/2009

Question
Hi,

The property is a condo complex located on St. Thomas in the US Virgin
Islands.  
Many areas of concrete in building structures on the island have a spalling
issue where the rebar beneath the concrete begins to rust and subsequently
the concrete pops and breaks apart.  The issue we have is a foundation
extension that supports a stone wall facade has a spalling problem. The
extension is similar to what you would see under a brick front home.   What
would be the safest and proper way to do the repair?  Should we remove the
stone facade prior to addressing the spalling issue or can the stone be
supported while the repair is done?
Thank you, Andy

Answer
Hi andy, you might have to remove enough of the facade to do the repair work.  It sounds to me like your rebar should have been epoxy coated or galvanized to protect it from the salt in the island ground water.  Most coastal buildings have coated reinforcing steel for this reason.  I am not sure how extensive your repairs need to be.  If you can expose the steel, you might be able to get by with sand blasting the rust from it, coating it and recasting it with a patching cement or non shrink grout augmented with a latex bonding agent. I hope this information helps feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com