Cracked foundations need study by a state task force
I have been following the stories of troubled concrete foundations with great interest (and annoyance) as my 45-plus engineering career has been intimately connected to the concrete construction industry.
What I have been hearing from George Colli on NBC 30 and reading in the Journal Inquirer has the tone of a vendetta against the J.J. Mottes Co. The recent media articles give the perception that J.J. Mottes is the villain. I do not believe that an adequate case has been made that the company willfully and knowingly produced concrete with an inferior aggregate. I do not mean to downplay the seriousness of the problem. However, let’s keep in mind that concrete has evolved far beyond what was once a product made from locally sourced materials using a simple recipe. I expect we will ultimately learn that this is a situation where those involved can rightly say “Who knew?”
During the period of time when much of this allegedly defective concrete was produced, the effects of pyrite and pyrrhotite were just beginning to be studied, primarily by the mining industry, as well as some observed phenomena of swelling soils. Its adverse effect on concrete was little known outside of a few small localities that were beginning to see evidence of a problem in the 1990s. The concrete industry as a whole had not yet begun to recognize a connection between pyrrhotite and self-destructing concrete.
There are two known deterioration mechanisms that present in a very similar manner – one is alkali silica reaction and the other involves the presence of pyrrhotite in the coarse aggregate (stone) used to produce concrete. I will not go into great detail to describe how these reactions take place. But I can tell you that it takes a long time – perhaps 8 to 15 years or more – before the problem becomes evident. The media reports aptly describe the visual clues that indicate there may be a problem.
From what I have learned, there are a number of factors that can contribute to or exacerbate the problem. Concrete is produced from a combination of coarse stone, sand, cement and water. Current concrete technology also adds a number of additional ingredients (admixtures) to enhance both the fresh and the hardened concrete’s properties. If pyrrhotite is present in the stone, water and oxygen will foster the chemical reaction that produces the expansive byproducts. Unfortunately, both water and oxygen are present in concrete.
What really needs to be determined is how the problem can be mitigated. Many of the foundations I have observed, while showing evidence of the cracking associated with alkali silica reaction or pyrrhotite, are not structurally unsound as they currently exist. We do not yet know what specific conditions foster the deterioration. I have seen foundations whose concrete came from a single source yet only portions of the foundation show evidence of the suspected pyrrhotite deterioration. I do not believe that the mere presence pyrrhotite alone is the sole cause, as it (and pyrite) are minerals commonly found in varying concentrations in igneous rock. Note that igneous and metamorphic rocks make up a high proportion of the accessible rock quarried in Connecticut.
What also concerns me is that no warnings have been published by the media to advise troubled homeowners to be wary of scams involving ineffective repairs and bogus investigations. I have seen an advertisement by a basement waterproofing company (with no history in Connecticut) that claims it can resolve the problem. I have seen reports from an engineer who had essentially condemned two home foundations as being plagued with cracking due to alkali silica reaction and suggested that the best course of action would be to replace the foundation. One of those foundations exhibited little or no significant visible evidence; the other had been “repaired” such that most of the original foundation was not visible. For what it matters, the engineer was retained by the buyer.
The reality is that there are a number of foundations that have been drastically affected by the pyrrhotite issue, and the current prevailing opinion is that the only permanent fix is a foundation replacement. However, I maintain that in many instances, there is a compromise solution that, while not eliminating the problem, may bring the internal chemical reaction to a gradual halt. Many of the homes with the early signs of the problem are not structurally challenged, in spite of the appearance issues that would make one think otherwise. The width of the cracks that exist can easily be monitored to indirectly assess the speed of the internal reaction (and the associated deterioration) so that one can then judge the urgency to consider a permanent remedy.
The pyrrhotite problem was found in an area of Quebec as well. Perhaps the Cement Association of Canada could provide some insight. A competent petrographer – one who delves into the description and systematic classification of rocks – can confirm the existence of pyrrhotite in concrete, but the cost of the lab work is beyond the means of the average homeowner. While the diagnosis is helpful, it still does not provide the means to resolve the homeowners’ threat to their investment.
The task force that has been suggested is an absolute necessity. However, a task force over-represented by politicians and attorneys is not the answer. I believe there is a common thread to all of the foundations that have suffered extreme deterioration—we just do not yet know what that thread is. The concrete industry as a whole needs to step up and assist the task force by providing their expertise and research. Therefore, this task force must be comprised of individuals with a comprehensive knowledge of concrete and its chemistry, as well as knowledge of how concrete is handled during the construction of residential foundations.
There are a number of trade and technical organizations that should be consulted, such as the National Ready Mixed Concrete Association, the American Concrete Institute, the American Society of Concrete Contractors, the International Concrete Repair Institute, and perhaps the American Society of Civil Engineers. These organizations have people with the technical expertise to help determine why this phenomena is so prevalent in northeastern Connecticut.
I believe that the media and our politicians must devote more effort to pressuring the industry to invest in research to learn how to prevent and mitigate the problem and spend less time and effort on vilifying one small concrete producer that started many decades ago as a “mom and pop” operation.
I urge Gov. Dannel P. Malloy and our state legislature to get this task force assembled as quickly as possible. I also urge members of the industry groups mentioned to lobby their leaders to get involved. The task force must attack these three challenges:
- Determining how to prevent this from occurring
- Finding effective and affordable remedial measures for mild degradation
- Determining how to financially assist those who have been adversely affected.
I would be grateful for the opportunity to participate in this effort.
Ralph H. Tulis is a professional engineer whose business is Structures Consulting in Willington.
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