Home Foundations Are Crumbling. This Mineral Is to Blame.
In 2020, Karen Bilotti and her husband, Sam, started to notice fine lines in their basement’s concrete walls. Ordinarily, they might not have given them a second thought. But the Bilottis had recently heard about a growing group of nearby homeowners in Massachusetts with larger cracks in their foundations, and Sam began to worry.
“‘With our luck, our house is probably affected,’” Karen recalled him saying. “And I’m like, ‘You’re crazy. You’re absolutely ridiculous. There’s no way.’”
Through core testing, scientists and engineers had determined the culprit behind fissures like those in their neighbors’ homes was pyrrhotite, a mineral made up of sulfur and iron found in some concrete aggregates. When exposed to air and water, pyrrhotite can break down into secondary minerals that cause foundations to fracture, structural integrity to erode, and home values to tank.
“It’s like your house was diagnosed with cancer,” said Michelle Loglisci, a founder of Massachusetts Residents Against Crumbling Foundations, a grassroots organization of homeowners fighting for legislation and financial relief in their state.
It wasn’t the first time the Bilottis had faced a housing catastrophe. Back in 2011, a tornado tore through Western and Central Massachusetts, corkscrewing the frame of their previous home off the foundation like a twisted dollhouse.
The Bilottis didn’t want to rebuild. So they bought a home in another part of town — “our dream house,” Bilotti said — thinking they’d put their bad fortune behind them. And now that dream home faced an uncertain future.
Sure enough, a test revealed they were positive for pyrrhotite. Like scores of other Massachusetts homeowners, they faced a grim decision: live with the knowledge that their house’s foundation was gradually failing, or pay as much as $300,000 to replace it without any guarantee of future support from the state.
“It’s like your house was diagnosed with cancer.”
For years, public officials in the U.S. associated this real estate nightmare with Connecticut, where investigators attributed one quarry’s pyrrhotite-contaminated aggregate to as many as 35,000 faulty foundations in the state. But the increasingly sprawling reports of crumbling foundations in Massachusetts have heightened concern among scientists and homeowner advocates that defective concrete is a more widespread problem — one with little current or historical oversight — than previously understood. Recently, a condo complex with a cracking foundation in Dracut, Massachusetts, just south of the New Hampshire border, tested positive for pyrrhotite. Beyond New England, pyrrhotite from two known quarries in Canada has damaged thousands of homes since the 1990s, and studies over the past two years revealed its deteriorative effects as far as Ireland.
The discoveries in these regions have undergirded a nascent area of scientific inquiry. Last May, the first International Conference on Iron Sulfide Reactions in Concrete included presentations on testing for pyrrhotite, understanding its reactivity, and mapping the mineral.
The conference, too, revealed a quarry in Massachusetts that had tested positive for pyrrhotite. Some researchers think there may be more: “There have to be other quarries,” said Kay Wille, principal investigator of the University of Connecticut’s Crumbling Concrete Research and Testing team.
Without widespread enforced testing for pyrrhotite, scientists can’t determine the extent of defective concrete, or how to contain its spread. “It may happen everywhere if you don’t have the regulation to ensure it doesn’t happen,” said Pierre-Luc Fecteau, a researcher at Université Laval who helped organize the conference in Canada.
To clear high regulatory bars, concrete suppliers typically “test for everything,” said Craig Dauphinais, executive director of the Massachusetts Concrete & Aggregate Producers Association, a trade group that represents the concrete industry in Massachusetts and Rhode Island. But Connecticut didn’t require quarries to report sulfur content and, in some cases, pyrrhotite until 2022, and Massachusetts only passed a law requiring quarries to test for sulfur compounds in 2023, though testing has not yet started, said John Goggin, a communications analyst at the Massachusetts Department of Transportation. Until Connecticut traced its cracking foundations back to a concrete supplier in its state, pyrrhotite wasn’t on the industry’s radar, according to Dauphinais.
“Nobody knew about this mineral,” he said. “Nobody knew that there was an issue with it related to ready-mix concrete.”
Pyrrhotite is easy to overlook. The bronze mineral remains less prevalent than pyrite, a fellow iron sulfide known as fool’s gold. But like its lucrative-looking kin, the uncommon mineral has become known for its deception — for blending into sturdy concrete while, very gradually, crumbling it.
Pyrrhotite doesn’t cause this deterioration by itself. When the highly reactive iron sulfide encounters water and oxygen, it transforms into sulfate minerals — ettringite, thaumasite, and gypsum — that occupy more space than the pyrrhotite they’re replacing. This expansion in volume pressures the surrounding mix of aggregate, cement, and water in concrete, forcing it to crack. This phenomenon is called an internal sulfate attack.
“It’s like a process which is very difficult, challenging to slow down or to stop or prevent,” Wille said.
For a long time, the attack happens under the surface and can take anywhere from 10 to 30 years for cracks to appear. But once the splintering starts, Wille explained, the concrete’s degradation accelerates, as the fissures expose pyrrhotite to more moisture and oxygen.
Entrenched in bedrock, the mineral was long protected from these elements at Becker’s Quarry in Willington, Connecticut. But when the JJ Mottes Company started sourcing stone from the site in the early 1980s, the supplier unwittingly introduced pyrrhotite to the natural forces that cause it to break down.
As is the case today, many factors could have contributed to crumbling foundations, such as temperature changes, poor drainage, or alkali-silica reactions, another chemical phenomenon that can degrade concrete from within. “It’s not surprising if concrete cracks,” Wille said. No one definitively connected this form of structural failure in Connecticut to pyrrhotite until the 2000s.
In 2016, after Wille and a graduate student on his team discovered pyrrhotite in core samples from concrete basement walls, they attributed the crumbling concrete to sulfate attacks. By the next year, the state had received more than 550 reports of homes with failing foundations, and it later determined tens of thousands more were at risk, as the concrete originated from the widely used JJ Mottes Company up through 2015. “Originally, we just kind of assumed this is the only quarry that was involved,” said Nick Scaglione, the president of Concrete Research & Testing, a laboratory in Ohio that identified pyrrhotite reactions as the cause of cracking in Connecticut back in 2008.
“Nobody knew about this mineral. Nobody knew that there was an issue with it related to ready-mix concrete.”
Around that time, and unbeknownst to many in Connecticut, hundreds of homeowners in Quebec, Canada were in the middle of their own protracted battle with pyrrhotite and a construction company. A geologist from the corporation then known as SNC-Lavalin, now AtkinsRéalis, had approved the use of concrete contaminated with the mineral, which builders then used in thousands of homes. The crumbling concrete manifested more rapidly than in Connecticut, and with insufficient financial support available, some families fell into financial ruin. “It was a nightmare,” said Alain Gélinas, who heads a coalition representing fellow victims of pyrrhotite.
Gélinas discovered cracks in his basement in 2012. A few years later, he traveled to Connecticut to meet with a group of homeowners. He was struck by the similarities in their plights, specifically how one company could be responsible for so much suffering. “It was a copy and paste of what we went through here,” Gélinas said.
In Massachusetts, many would soon start to see the same telltale cracking in their foundations. Like in other areas with documented pyrrhotite problems, Massachusetts at least partially reimburses eligible homeowners who order tests from contractors.
But Wille and other researchers are still refining those tests. At the University of Connecticut, for instance, they’re studying how specific quantities of the mineral relate to future concrete damage, part of a global effort to understand why foundations are crumbling in North America, and beyond.
Last May, about 75 scientists, consultants, builders, and other experts gathered on the campus of Université Laval in Quebec City for the first International Conference on Iron Sulfide Reactions in Concrete.
Over four days, researchers discussed everything from advances in electrochemical sample testing to broad geological mapping. Some cited the 2020 U. S. Geological Survey map of potential areas of rock with pyrrhotite, with a vast vein running through the Appalachian Mountains. But both the report’s co-author, Jeff Mauk, and other scientists caution that the map doesn’t account for factors such as the amount of the mineral or its reactivity level.
“Originally, we just kind of assumed this is the only quarry that was involved.”
“That map can be really kind of misleading,” said Scaglione. “I would not look at that map and say, ‘Wow, we could have a really widespread problem here based on this map.’ We don’t know.”
Follow-up testing at quarries is vital, said Fecteau: “You can’t get around that if you want to be sure.”
While researchers at the Quebec City conference hailed from Japan and Norway and Portugal, among other countries, they tended to focus on the problem of crumbling concrete in three known hotbeds: New England, Quebec, and, of more recent concern, Ireland.
Since gaining public recognition in 2013, a spate of crumbling buildings in Ireland has been known as the mica crisis or scandal. A panel commissioned by the Irish government attributed structural defects in multiple counties to pyrite and, more widely publicized, muscovite mica, a mineral that absorbs water. When the mica freezes and thaws, the panel concluded, its fluctuating size roils the surrounding concrete. After years of property owners campaigning for support, the government started a grant scheme to help rebuild people’s homes.
But in two recent studies published in Cement and Concrete Research, scientists reported that the Irish government’s “desktop review” may have overlooked the primary cause of the crisis. Pyrrhotite oxidation, not mica’s absorption of water, was driving the concrete apart, their chemical analyses of building material showed. “At the moment, the entire scheme is based on testing for the wrong thing,” said Paul Dunlop, a glaciologist at Ulster University who co-authored the studies after an engineer told him his walls tested positive for pyrrhotite.
“I would not look at that map and say, ‘Wow, we could have a really widespread problem here based on this map.’ We don’t know.”
In Quebec City, Dunlop shared his team’s discoveries and found researchers with similar focuses in Canada, the U.S., and other countries. “You see the exact same secondary sulfate minerals being produced elsewhere in other concretes around the world,” he said. “So, in a way, it’s sort of affirmation that you’re on the right track.”
The conference confirmed affected homeowners in Massachusetts like Loglisci were on to something, too. In a written abstract of one of the conference presentations, Scaglione and a colleague reported that pyrrhotite-contaminated aggregate in at least one crumbling Massachusetts foundation was “lithologically distinct” from the aggregate found in Connecticut. It didn’t come from the quarry there but one in Rutland, Massachusetts.
But even as the problem crept into counties closer to the Massachusetts State House in Boston, legislation to support homeowners remained elusive. Earlier this year, lawmakers stripped away a plan to provide financial relief akin to Connecticut’s from the state’s Affordable Homes Act. On Oct. 30, members of the Massachusetts Residents Against Crumbling Foundations visited Beacon Hill to advocate, once again, for financial relief.
“After seven years of fighting for this, it wears on you,” Loglisci said, “and you just get frustrated, and you just want somebody to do something — to actually do something.”
Scientists are conducting further research on how the amount of pyrrhotite, the different varieties of the mineral, and the water content in concrete affect the damage to foundations. In the meantime, families can only guess how long their crumbling foundations will support their walls.
For now, Karen Bilotti and her family are holding off on replacing theirs. They received a $300,000 estimate to lift a house that cost them $500,000. They can’t afford it.
“I wish I had a money tree growing in my backyard,” she said, “but I do not.”
What was once their dream home is now, as Bilotti put it, “a nightmare.” Unlike the tornado, it haunts them every day. “This, I think, is almost worse,” she said. “Because there’s no end in sight.”
Benjamin Cassidy is a New England-based journalist whose work has appeared in Scientific American, National Geographic, Nautilus, and Smithsonian, among other publications.