International research scotches 'mica' myth

The ‘register’ of properties affected by defective concrete products and blocks established by Derry City and Strabane District Council should not be restricted to the minerals, mica, pyrite and pyrrhotite, according to a member of Donegal County Council.

Cllr Frank McBrearty, himself an affected homeowner, said it was vital Derry City and Strabane District Council’s definition be widened to include “all deleterious materials and all reactive sulphide minerals”.

What Council described as its ‘data collection exercise’ followed a home here being described as the first in the North with a confirmed case of ‘mica’, in November 2022.

The home belonged to Danny and Kate Rafferty, from Beragh Hill Road in the Skeoge area of the city, who carried out testing on their blocks when telltale ‘spider cracks’ appeared on the outer wall and chimney of their house.

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Speaking to Derry Now, Cllr McBrearty said: “As a result of two years of investigation, undertaken by Derry’s Dr Ambrose McCloskey, chartered engineer and IS465 registered engineer;  and Kieran Coyle, chartered structural engineer; and international experts, Professor Paul Dunlop and Dr Andreas Leemann; other experts from Canada, US and Norway;  and myself, I believe, Derry City and Strabane District Council must now look at an investigation into all deleterious materials and reactive iron sulphide minerals, which could possibly be present in properties in the North of Ireland, constructed with concrete products bought from Donegal.” 

“The people of Derry and Tyrone should not be hoodwinked into believing this is a ‘mica’ issue. 

“The words, ‘all deleterious materials and all reactive sulphide minerals’ must be included and a full, transparent investigation conducted by professionals like Professor Paul Dunlop, Ambrose McCloskey, Kieran Coyle, the engineer acting for our family,  and others, if necessary. 

“We do not know how bad the situation is in the North because there is no oversight or policing of the industry in Donegal. This is going to manifest over time and affected properties will become uninhabitable,” said Cllr McBrearty.

Cllr McBrearty's research document can be read HERE.

Cllr McBrearty’s warning came as Ulster University academic, Professor Paul Dunlop, and four colleagues published their newly peer-reviewed paper, which can be read by clicking this link: "The ‘mica crisis’ in Donegal, Ireland - a case of internal sulfate attack?” 

The paper confirmed that geological mineral mica was not the primary cause of failure of defective concrete blocks in Donegal homes, rather it was the mineral pyrrhotite present in the aggregate found in defective blocks in the county.

Co-authored by Dr Andreas Leemann; Professor Barbara Lothenbach; Dr Beat Münch of Empa’s Laboratory for Concrete and Asphalt, Switzerland; Thomas Campbell, TA Group, Ireland and Professor Dunlop, School of Geography and Environmental Sciences, Ulster University, the paper was published in ‘Cement and Concrete Research’.

According to Professor Dunlop this is the number one ranked journal internationally for Building and Construction.

Speaking to Derry Now, Professor Dunlop said: “Our research is the first internationally peer reviewed article that provides clear scientific evidence that defective concrete blocks in Donegal are failing as a result of internal sulfate attack directly connected to the presence of highly unstable pyrrhotite and not the mica freeze-thaw process as was proposed by a government report published in 2017 and incorporated into the National Standards Authority of Ireland (NSAI) testing and remediation standard IS465.

“This new scientific evidence is important for the government officials and policy makers who are dealing with the defective concrete block crisis to ensure science based solutions are at the heart of government solutions for affected homeowners.

“Its publication is also timely for the NSAI which has been calling for rigorous, independently peer reviewed scientific data for its ongoing review of IS465.

“In addition, it provides information for the National Building Control and Market Surveillance Office which is tasked with market surveillance about the obvious risks for concrete failure when aggregates containing pyrrhotite are used and reinforces the need for robust surveillance of the extraction industry and concrete manufacturers,” said Professor Dunlop.

Derry City and Strabane District Council has subsequently issued a public call out to property owners in the area, who have evidence that their residence / dwelling has been impacted by mica, as certified by an authorised mica testing organisation, to get in contact with it so it can add their details to the database.

Council stressed the purpose of this exercise was to collate data only as it could not carry out any form of ‘mica’ testing.

It said: “This data collection exercise will allow Council to quantify how many homes / properties within the Derry and Strabane District have already been tested and deemed to be affected by mica.

“Property owners are urged to get in touch by sending their name, details of the affected property and contact number, along with a copy of certified testing / documented evidence to prove your property has been impacted by mica to the following bespoke email address: mica@derrystrabane.com.

“The information will be collated and presented to a further meeting of the Council’s Environment and Regeneration Committee for elected members to review and consider going forward.”