Canadian Pyrrhotite Problem

The Canadian pyrrhotite problem

Last updated 20.09.16


For details of the USA Connecticut and Massachusetts pyrrhotite problems, please click here.

The following historical summary is a work in progress which details the Canadian problems associated with the iron sulfide mineral pyrrhotite. Canada also has a history of pyrite problems, in 1996 (Montreal) and in the 1970s and 1980s. This summary generally considers only the events related to the recent (year 2000 and after) pyrrhotite crisis.

Pyrrhotite is an iron sulfide mineral with the general chemical composition Fe(1-x)S. It is widely reported as much more reactive (prone to oxidation) than pyrite (see review in Hawkins and St. John, 2013). Research on Canadian pyrrhotite problems has been published by Duchesne and Fournier (2011 and 2013) as well as Rodrigues et al., (2012). The oxidation of this mineral, which was identified in the aggregates of concrete foundations, has been deemed the cause of damage to thousands of homes.

In the early 2000s around 30 homes suffered pyrrhotite problems in the Trois Rivieres area of Quebec, relating to aggregates from a small quarry that only operated for a short time (Maher, 2013). New problems came to light in the late 2000s, with around 1700 residential buildings now suspected of having pyrrhotite problems. Events are still unfolding so keep checking back for updates.

Sources and Disclaimer

Unless otherwise stated, these events are summarised from the Canadian news website La Presse (, mostly from the news paper Le Nouvelliste (translated from French using Google translate). The date at the end of each event refers to the publication date of the corresponding story on the relevant news website, so that readers can locate the article (if not linked directly).

The summary does not purport to be complete and whilst I have made every effort to ensure accuracy, mistakes are possible, particularly considering the translation required. Caution should be exercised when reading and interpreting these events. Any interpretation or use is at the reader’s risk. Attention should be paid to the original source and its validity. Please get in touch with any corrections, additions or revisions. I welcome any feedback and comments.

Historical Summary


April: Global News reports that “Ottawa to spend $30M on helping Quebec homeowners who have pyrrhotite”. (06.04.16).

March: Le Nouvelliste reports that the Coalition of Victims of Pyrrhotite “…wants to tackle rising repair costs”. (29.03.16).

March: News article on Le Nouvelliste by a pyrrhotite victim suggests that “In view of the amount of $30million over three years, a quick calculation made me conclude that the amount would be exhausted as early as August.” (28.03.16).

March: Le Nouvelliste reports “Federal Budget: $ 30 million over three years for pyrrhotite”. (22.03.16).

February: Le Nouvelliste reports “Pyrrhotite: finally some optimism” and discusses a meeting of the Coalition for Victims of Pyrrhotite. (15.02.16).


November: Le Nouvelliste reports that “…victims of pyrrhotite have until April 30, 2016 to report their situation…” for evaluation. The article suggests there are 1672 cases currently reported. (03.11.15).

November: Le Nouvelliste provides further information on the valuation of houses with pyrrhotite problems. (03.11.15).

October: Le Nouvelliste reports that “…houses affected by pyrrhotite are now valued at 40% of their original value.”. (29.10.15).

October: Le Nouvelliste reports that Stephen Harper has reiterated that the problem of pyrrhotite in Trois-Rivières and i”remains a case within the provinces and not the Canadian government”. (15.10.15).

October: Le Nouvelliste reports that house prices in Trois-Rivières have dropped by 3.3% compared to the third quarter of last year. (14.10.15).

October: Le Nouvelliste provides a summary of the pyrrhotite problem: (translated from French)

Since 2011, Quebec has already injected $ 30 million to support victims of pyrrhotite, but not a penny came from Ottawa...” “…Recall that victims of pyrrhotite had won their case at trial in June 2014. In July 2014, SNC Lavalin has decided to bring the appeal.(13.10.15).

September: Le Nouvelliste reports that the Liberal leader Justin Trudeau used his stop in Trois-Rivières on Wednesday 2nd September to pledge financial support to victims of pyrrhotite. (02.09.15).

June: Le Nouvelliste reports that the Coalition for victims of pyrrhotite has observed a slowdown in demand from the victims. (29.06.15).

June: Le Nouvelliste reports on the successful nomination to candidature of Yvon Boivin to the Liberal Party of Canada. Yvon confirmed a commitment to the victims of pyrrhotite. (22.06.15).

May: Le Nouvelliste reports on the pyrrhotite victims Solidarity March which took place in Trois Rivieres with around 3000 participants (30.05.15).

Videos of the Solidarity March from YouTube:

May: Le Nouvelliste reports that the new CVAP president is now Alain Gélinas. (29.05.15).

May: Le Nouvelliste reports that the CVAP intends to continue its mission. (27.05.15).

May: Le Nouvelliste describes some case studies of victims of pyrrhotite. (26.05.15).

May: Le Nouvelliste reports that the founder and leader of the CVAP, Yvon Boivin has decided to step down from the role to pursue a role in politics as a candidate for nomination to the Liberal Party, with the aim of continuing to support victims of pyrrhotite. (26.05.15).

May: Le Nouvelliste reports that the experts on pyrrhotite believe the > 0.23 % pyrrhotite content in concrete as a damage threshold has no scientific basis. The experts also criticize the test for pyrrhotite in concrete undertaken by testing laboratories. (05.05.15).

April: Le Nouvelliste reports that the Budget announced in Ottawa does not include financial assistance for victims of pyrrhotite. (22.04.15).

April: Le Nouvelliste reports that a new CSA Standard relating to pyrrhotite in concrete has been published. The article reports that a maximum tolerable pyrrhotite content has not yet been defined. Results of testing may be incorporated into a new publication in 2019. (21.04.15).

April: Le Nouvelliste reports on the responses of eight municipalities in Mauricie and Centre-du-Quebec to a request for financial support from the CVAP. (21.04.15).

April: Le Nouvelliste reports that Ottawa has refused to provide financial assistance to victims of pyrrhotite. (14.04.15).

April: Le Nouvelliste provides a background to the pyrrhotite legal case. (14.04.15).

  • Procedures served from 2009
  • Two years of case management before trial
  • Judge appointed in January 2010
  • The trial took place in 2013 and 2014
  • 40 days of interrogation before trial
  • Less than 80 days trial
  • 60 lawyers involved
  • 22000 documents filed in court
  • 69 causes combined
  • 857 files
  • Case appealed in 2014

March: Le Nouvelliste reports on the removal of pyrrhotite-damaged foundations from the a clock-tower building in Trois Rivieres (25.03.15).

March: CVAP uploads a video to YouTube on the pyrrhotite problem:

March: Le Nouvelliste reports on the discovery of pyrrhotite problems in northern Montreal. (12.03.15).

February: Le Nouvelliste reports on fraud charges against SNC-Lavalin and the implications for victims of pyrrhotite. (23.02.15).

February: CVAP uploads a video to YouTube on the pyrrhotite problem:

February: Le Nouvelliste reports that the Coalition for Victims of Pyrrhotite (CVAP) has requested four years of counseling for victims of pyrrhotite, to the Agency of Health and Social Services. (02.02.15).

January: Le Nouvelliste reports that the judgment of the appeal by SNC-Lavalin could be made in 2017. (23.01.15).

January: Le Nouvelliste reports that the Régie du bâtiment du Québec has refused access to a long-awaited university study on the causes of the deterioration of concrete by pyrrhotite. (23.01.15).

January: Le Nouvelliste reports that SOS Pyrrhotite has a filed a request for investigation to the Competition Bureau of Canada on the price charged by some contractors to rebuild the foundations of houses affected by pyrrhotite. (21.01.15).

January: Le Nouvelliste reports on a homeowner who has suffered with pyrrhotite problems in foundation concrete for a second time, despite a report indicating the aggregate was of acceptable quality. (19.01.15).

January: Le Nouvelliste reports on the first case of pyrrhotite in Hérouxville, in a building constructed in 2004. (13.01.15). An update on other buildings affected by pyrrhotite is provided:

  • Center of sport and physical activity at UQTR,
  • Alphonse-Desjardins Sports Complex
  • Ambulance of Cooperative Mauricie
  • 10 buildings of the City of Trois-Rivières
  • Four-lane bridge in Louiseville belonging to the Ministry of Transport

January: Le Nouvelliste reports a pyrrhotite problem at the Centre for Physical Activity and Sport and the new pavilion of Health in Trois-Rivieres. (09.01.15).


December: Le Nouvelliste reports that “it costs between $2,800 and $3,300 to do a complete test for pyrrhotite” in concrete. An update on the pyrrhotite problem is provided: (19.12.14).

  • Five to 10 new cases per week
  • Some 4,000 potential victims
  • Over 2,000 reported victims
  • Losses of $12m in taxes for Trois-Rivières
  • No financial assistance from Ottawa
  • $32m cumulative with Quebec

December: Le Nouvelliste reports that the City of Trois-Rivieres has confirmed the renewal of its financial assistance to the Coalition for victims of pyrrhotite for the years 2015, 2016 and 2017. (03.12.14).

November: Le Nouvelliste reports that on average ten new victims of pyrrhotite seek help each week. (28.11.14).

November: Le Nouvelliste reports that “…victims of pyrrhotite will have to wait a year, maybe two, before knowing if and how they will be compensated for damage to their house by pyrrhotite.” (13.11.14).

October: Le Nouvelliste reports that $7 million has been made available for victims of pyrrhotite in Mauricie. (24.10.14).

October: Le Nouvelliste reports that “A dozen victims of pyrrhotite heaved a sigh of relief Monday as the arbitrator who heard their case against the New Home Warranty APCHQ in September ruled in their favor.” (07.10.14).

October: Le Nouvelliste reports that the average cost of remediation per house is $182,000 per house. (06.10.14).

September: Le Nouvelliste reports that the pyrrhotite appeal by SNC-Lavalin has been dismissed due to prematurity. (25.09.14).

September: Le Nouvelliste reports that “Recently, the City has conducted an analysis of 33 infrastructure built over the years 2003 to 2008, the most risk period for pyrrhotite.” (16.09.14).

September: Bruno Nantel provides an update on the pyrrhotite problem at the International Housing and Home Warranty Conference. Click here to read the full update presentation. (07.09.14).

September: Le Nouvelliste reports that “The first judgment in the case of pyrrhotite concerned 69 cases, affecting 814 properties alone representing a total of $ 158 million. The Coalition of victims of pyrrhotite believes that all damage Mauricie and Centre-du-Québec imposed by pyrrhotite quarried B & B Saint-Boniface can easily reach $ 1 billion.” (02.09.14).

August: Some homeowners with pyrrhotite problems receive letter asking that homes be removed from the 2014 repair scheme. (26.08.14).

August: Video uploaded to YouTube showing time-lapse demolition of a house damaged by pyrrhotite in Trois Rivieres (26.08.14):

August: Quebec residents await decision as to whether further funding will be provided for the pyrrhotite problems. (08.08.14).

August: SNC-Lavalin justifies appeal based on grounds that the Judge wrongly assigned blame for the pyrrhotite problems. (05.08.14).

July: Le Devoir (11.07.14) reports that the Canadian Standards Authority will issue new aggregate standards in the coming weeks. According to Le Devoir (12.07.14), it will include a specific annex to deal with iron sulfides. There had been calls for the new standard to adopt the acceptable total sulfur level of 0.1 % S if pyrrhotite is present, as is currently stipulated by European standards for aggregates for concrete (EN 12620). The Ottawa Government had said in June that there would be no changes to standards.

July: SNC-Lavalin announce that they will appeal the judgement made in the pyrrhotite trial. (10.07.14).

July: Le Nouvelliste reports that some homeowners may appeal to lower the minimum pyrrhotite level required for compensation. (10.07.14).

July: Le Nouvelliste reports on pyrrhotite-affected homeowners that may not be compensated due to the low level of pyrrhotite found. (10.07.14).

June: Pyrrhotite victims (CVAP) urge SNC-Lavalin not to appeal judgement in the pyrrhotite trial. (14.06.14). A petition of some 600 names is signed and submitted to the Regional Minister. (19.06.14).

June: News reports 1700 residential buildings with pyrrhotite problems. (13.06.14).

June: News reports part of Judge’s comments on pyrrhotite trial, noting > 0.23 % pyrrhotite (by volume) was the expected level for problems. Judge states that “the sole cause of the damage results from the oxidation of pyrrhotite in the aggregate”. (13.06.14). A summary (in French) of the verdict can be found here.

June: SNC-Lavalin releases short press statement acknowledging judgement in trial.

June: Judgement delivered in pyrrhotite trial. 30 days for appeal given. (12.06.14).

Major findings:

  • SNC-Lavalin and their geologist Alain Blanchette found responsible for 70 %
  • Concrete Laurentide and/or Construction Yvan Boisvert found responsible for 25 %
  • 5 % responsibility with building contractors.
  • Joint liability to pay $ 196 million to victims of pyrrhotite ($ 158 million residential, $ 38 million commercial).
  • Defendants may appeal the judgement, sums not payable until judgement final.
  • Trial lasted 68 days over one years, with 185 witnesses, chaired by Judge Michel Richard.
  • Considered the time period 2003-2008, with 850 registered pyrrhotite victims.
  • Judge indicated B &B Quarry was already aware of the pyrrhotite problem, particularly considering the Maskimo Quarry located so close.
  • First case of pyrrhotite was in a IGA supermarket.

March: Ottawa Business Journal reports that the Concrete Coalition has cut ties with the SOS Pyrrhotite group.

March: News reports that there is no proven alternative to replacement of foundations in the remediation of the pyrrhotite problem. (18.03.13).

February: Quebec Government announces $ 15 million to support victims of pyrrhotite. (04.02.14).

February: The Institut National de Sante Publique du Quebec publishes a report on the potential health risks of pyrrhotite in concrete and the associated damage to buildings. Click here to read PDF report.

January: Concrete Coalition proposes requesting $ 200 million from Governments of Quebec and Canada to support victims of pyrrhotite for next 5 years. (07.01.14).


December: Construction Yvan Boisvert (CYB) argues that it was unaware of the deleterious effects of the aggregate from Quarry B & B until 2008. (16.12.13).

November: Pyrrhotite trial ends (28.11.13).

November: News reports on updated list of pyrrhotite victims, now around 1500 homes. (26.11.13).

November: SNC-Lavalin strongly defends their geologist, Alain Blanchette, who is reported to have stated numerous times that the aggregates of the B & B Quarry was of good quality. (26.11.13).

November: Concrete Coalition proposes to produce a list of contractors that have taken advantage of pyrrhotite victims. (19.11.13).

October: News features a young couple that bought a $ 118,000 home in 2009, which is now worth $ 30,000 due to pyrrhotite in the concrete foundations. (31.10.13).

October: News reports a pyrrhotite waiting list extending to 2016. Discusses remediation proposals: 90 homes in 2014, 80 in 2015 and 100 in 2016. (24.10.13).

October: News reports average cost of pyrrhotite damage per home in the recent trial is $150,000 (22.10.13).

October: Concrete Coalition estimates cost of pyrrhotite problems at $ 1 billion. (10.10.13).

October: News reports that Expert Christopher Rogers suggests the acceptable limit of pyrrhotite in aggregates is zero. (09.10.13).

October: Pyrrhotite victims summarised as: 1300 homes, two sports centres, a health centre, a courthouse (ironically the same court house in which the 2012-2013 pyrrhotite trial was undertaken), a police academy, a Transport Ministry building, a hospital, a school, a bridge, an ambulance building as well as numerous other structures. (09.10.13).

September: News reports 1330 victims of pyrrhotite in Trois Rivieres, Coalition expects rise to 5000 over next few years. (16.09.13).

September: SOS Pyrrhotite demands Government study on health of pyrrhotite victims. (04.09.13).

September: City of Trois Rivieres provides additional funding support to Concrete Coalition. (04.09.13).

August: Duchesne and Fournier paper “Deterioration of concrete by the oxidiation of sulphide minerals in the aggregate” published in the Journal of Civil Engineering and Architecture. Paper considers pyrrhotite problems in Trois Rivieres. Abstract here.

August: City of Trois Rivieres announces that it will fund the Concrete Coalition. (24.08.13).

August: News reports $15 million pyrrhotite fund is exhausted. (23.08.13).

July: Additional $ 4.4 million announced for pyrrhotite victims from Quebec. (04.07.13).

June: SNC-Lavalin (main defendant in pyrrhotite trial) proposes two remedial solutions for pyrrhotite problems, claims would cost 50 % less than full foundation replacement. (27.06.13).

June: Concrete expert Kamal Khayat (for SNC-Lavalin) explains problems other than pyrrhotite in concrete required to have caused such major widespread problems. Reported permeability and density abnormalities. (17.06.13).

June: Engineering Geologist Charles Tremblay reports in court that the speed of concrete damage is (directly) proportional to the amount of pyrrhotite present. Tremblay also revises the damage threshold from 0.4 % pyrrhotite down to 0.2 % pyrrhotite based on new laboratory results. (11.06.13).

June: Engineering expert Michael Maher testifies in court concerning the aggregates sourced from the B & B quarry. Maher discussed the strength and permeability of the rock. (11.06.13).

June: Concrete Coalition spokesperson Yvon Boivin declares the pyrrhotite problem a “regional disaster” in light of the recent discovery of pyrrhotite in the Centre for Health and Social Services foundations. (06.06.13).

June: News reports on list of pyrrhotite-affected structures, includes 1200 residential buildings, a bridge and many commercial buildings. The damage is estimated as up to hundreds of millions of dollars. (06.06.13).

June: Pyrrhotite confirmed in foundations of the Centre for Health and Social Services foundations. (05.06.13).

June: Concrete Coalition seeks to employ a full-time staff member to deal with pyrrhotite crisis victims. (03.06.13).

May: Expert Michael Maher states that Laval University is developing a test to predict the damage caused by pyrrhotite in concrete. (31.05.13).

May: Expert engineer Frederic Gagnon states that pyrrhotite is the only cause of the concrete damage. (23.05.13).

May: Researchers from Laval University report (in court) on other quarries with total sulfur concentrations similar to those at Maskimo and B&B quarries. (22.05.13). Levels of 5-7 % sulfur are reported.

May: French Expoert Loic Divet testifies in court concerning oxidation of pyrrhotite. (16.05.13).

May: MPs note that the National Building Code of Canada (2010) has no standards for pyrrhotite in concrete (only pyrite). (15.05.13).

March: News reports that pyrrhotite damage could amount to $ 400 million. (30.03.13).

March: News reports that testing can cost $ 4,000 per analysis. (25.03.13).

March: News reports pyrrhotite-assistance program had 226 cases, of which 103 were settled, 24 were being settled and 99 were in analysis. (11.03.13). These 226 cases had used up to $3 million of the $15 million Quebec government funding when reported on 30.03.13.

February: News reports that pyrrhotite cases may continue to arise until 2020 or later. (13.02.13).

January: SNC-Lavin application to test concrete cores of foundations of pyrrhotite effected houses in US labs rejected by judge. (22.01.13).

January: Garantie Maisons Neuves publishes document “Dossier de la pyrrhotite a Trois-Rivieres”. (Published 08.01.13).


November: Court trial begins for pyrrhotite cases which occurred between 2003 and 2008. (07.10.13).

October: Paper by Rodrigues et al., (2012) titled “Mineralogical and chemical assessment of concrete damaged by the oxidation of sulfide-bearing aggregates: Importance of thaumasite formation on reaction mechanisms” published in Cement and Concrete Research Journal. Considers pyrrhotite problems in Trois Rivieres.

PhD Thesis concludes on pyrrhotite at UQAT (13.09.13).


Quebec announces financial assistance of $ 15 million for victims of pyrrhotite. (06.06.13).

Engineering Geologist Charles Tremblay reports that the damage threshold was 0.4 % pyrrhotite in aggregate. (11.06.13).

April: Duchesne and Fournier present paper titled “Petrography of concrete deteriorated by weathering of sulphide minerals” at the 33rd International conference on Cement microscopy, San Francisco, California (USA), April 17-20 2011. Paper considers pyrrhotite problems of Trois Rivieres.


November: Concrete Coalition (now Coalition of Victims of Pyrrhotite, CVAP) Facebook group created.

Concrete Coalition created – founded by Yvon Boivin. Boivin’s own home had pyrrhotite problems. (09.05.14).


Boisvert stops using aggregate from B & B quarry. (04.02.13).


Laurentide Concrete stops using aggregate from B & B quarry. (04.02.13).

February Further petrographic investigations on B & B aggregate. (04.02.13).


November: Extraction of aggregates ceases in Quarry B & B. (04.02.13).

Lafarge Canada recommends that Laurentide Concrete stop using aggregates from B & B quarry due to pyrrhotite. (15.02.13).

August: Further petrographic investigations on B & B aggregate. (04.02.13).

May: Petrographic studies on B & B quarry aggregates extracted in 2006 and 1999, as well as studies on aggregates from Maskimo quarry. (04.02.13).


Further petrographic investigations on B & B aggregate. (04.02.13).


Further petrographic investigations on B & B aggregate. (04.02.13).


Report produced by Geologist Alain Blanchette indicating aggregated from B & B quarry was adequate for concrete. (11.06.13).


May: Engineering geologist Marc-Andre Berube produces report on pyrrhotite in concrete for Laurentide Concrete. Berube recommends that the B & B quarry aggregates should not be used. (15.02.13). (26.11.13).

Maskimo quarry recieves first claim for cracked foundations. (31.01.13)


Laurentide Concrete seeks technical advice from Lafarge Canada over cracks in concrete structures in Trois-Rivieres. (15.02.13).

Laurentide Concrete recieves first claim for problems related to deterioration of concrete constructed with Maskimo Quarry aggregates. (04.02.13).

Early case of pyrite in foundations noted in Mauricie. (24.01.13).


The Quebec Technical Committee publishes CTQ-M100, a protocol for characterising the potential for swelling of aggregates. (See CTQ-M200 for notes).


Association of Engineering Geologists establish the Quebec Technical Committee to address problems related to swelling of under-floor fill containing pyrite in Montreal. (04.02.13).

Laurentide Concrete uses some aggregates from B & B Quarry.


Laurentide Concrete began using aggregates from Maskimo Quarry. (04.02.13).

Maskimo Quarry starts activities and first use of aggregates from quarry in concrete. The quarry is less than 500 m from the B & B Quarry. (31.01.13) (04.02.13).


Operations start at B &B quarry. (04.02.13).


Yvan Boisvert and Claude Bouvet partner (B&B) to purchase a quarry (“B & B Quarry”) and supply aggregate. (04.02.13).


Duchesne, J., and Fournier, B. (2011). Petrography of concrete deteriorated by weathering of sulphide minerals. Proposed Paper for the 33rd International Conference on Cement Microscopy, Omni San Francisco Hotel, San Francisco, California, U.S.A. April 17 – 20.

Duchesne, J., and Fournier, B. (2013). Deterioration of concrete by the oxidation of sulphide minerals in the aggregate. Jnl. Civ. Eng. Arch. 7 (8), 922-931.

Hawkins, A.B., and St. John, T.W. (2013). Iron sulphides and surface heating: further engineering considerations for the Dublin area. In: Implications of pyrite oxidation for engineering works. A.B. Hawkins (ed). Springer, Switzerland.

Maher, M.J. (2013). The Canadian pyrite experience and comparisons with the Irish problems. In: Implications of pyrite oxidation for engineering works. A.B. Hawkins (ed). Springer, Switzerland.

Rodrigues, A., Duchesne, J., Fournier, B., Durand, B., Rivard, P., and Shehata, M. (2012). Mineralogical and chemical assessment of concrete damaged by the oxidation of sulfide-bearing aggregates: Importance of thaumasite formation on reaction mechanisms. Cement and Concrete Research. 42, 1336, 1347.