There are several reasons why concrete fails to bond together. One cause that has been identified in Northeastern region of Connecticut is related to a mineral found in the aggregate called pyrrhotite.
How Pyrrhotite Can Damage Building Foundations
Pyrrhotite can cause concrete used for foundations, septic tanks, precast concrete products such as hatchways, stairs and more to fail by breaking down. The initial signs are what is called mapping cracks. Initially, mapping cracks are small and hard to see and eventually grow to be very large and cause shifting and movement to the product.
Foundation Inspection and Testing
There are 3 ways to evaluate a concrete foundation for Pyrrhotite:
- Visual inspection. This is limited and is hard to pick up small cracking in the initial stages
- Solution spray. This is applied to the foundation and highlights cracks that cannot be seen with the naked eye. This will help when looking to see if the foundation has started to react to the pyrrhotite and is in the initial stages.
- Core samples, also known as core taps. This is when we cut a approx. 4” round opening in the foundation in 2 or 3 locations and take the concrete out for lab analysis. The hole is then filled properly to prevent leaking and the samples are labeled and sent to the lab. Once the lab evaluates the content they provide a report that provides the amount of “Pyrrhotite” in the core samples. This process has been recommended from the state of Ct. to get on the list for assistance.
Each of these methods can be used by your inspector to evaluate the foundation for structural damage if they have the proper knowledge of what to look for.
Our inspectors have examined hundreds of foundations for pyrrhotite in the past 3 years. If you have any questions about your foundation, give us a call at 860-646-9983 and one of our inspectors will be glad to assist you!