How does it relate to our homes?
In reading the news about the Surfside Condominium collapse in Florida last year, I am struck by all the things that sound familiar. Rising sea levels around the concrete basement. Leaking swimming pools that are elevated above the structure. Reported cracking of reinforced concrete. All of these combine to create a perfect storm of problems.
Fact: Water with salt in it is far more corrosive than simple water.
That awful and spectacular collapse shocked America, killing 98 people in one of the worst building collapses in many years. Many of us were shocked that something that should have been designed to avoid sudden collapses, did in fact suddenly fail in a very scary way.
Over time, rising sea levels brought salt water up higher and in more contact with the concrete basement. Water with salt in it is far more corrosive than simple water. Dr. Randall Parkinson from Florida International University has been documenting the rise of seawater on Florida coastlines. The NOAA data gathered within 10 miles showed nearly a tripling of hourly underwater events from 2006 to 2020. This salty water penetrated the concrete and left it vulnerable to corrosion of steel embedded in it.
Pools with chlorine in them also are highly corrosive to steel embedded in concrete. Frank Morabito, PE, owns Morabito Consulting and provided a report to the Surfside owners showing significant deterioration of rebar embedded concrete columns with highly congested rebar. Highly congested rebar means that it likely did not get full coverage of concrete around it leaving pockets or voids and making it vulnerable to corrosion and weakening it.
I lay out in detail in previous blogs the cycle of failure from concrete “rust jacking” (Repairing a Stem Wall Repair). Rusting rebar can exert up to 9000 pounds per square inch on concrete as it grows up to 5 times its size. Concrete only has between 300 and 700 psi of tensile strength capacity depending on its compressive strength. Tensile strength is the opposite of compressive strength. It is the ability of concrete to resist pulling it apart as opposed to crushing it. From this it is easy to see that concrete does not stand a chance once rust jacking starts.
It is not all that different in many stem wall problems we see in the Phoenix and Tucson areas. We commonly see whole neighborhoods where the rebar is oxidizing in the concrete, resulting in a horizontal crack in the stem wall (see What is a Stem Wall). The stem wall holds up the walls of a house which hold up the roof. If the stem wall fails, the stability of the walls and roof can be jeopardized. As we have noted with the Surfside Condominiums, these failures can be sudden and catastrophic.
What is the best way to protect yourself and your investment? Have your stem wall regularly inspected by a qualified Foundation Repair Contractor. If horizontal cracks appear, have them repaired with a system that will last….as noted in earlier blogs (Repairing a Previous Stem Wall Repair), many repairs return quickly if the contractor does not understand the electrochemical currents in the concrete and have a good plan to eliminate them.
Protect yourself and your investment. Schedule regular concrete stem wall inspections with professional Concrete Repair and Foundation Repair Experts: 1-844-924-8900.
