New international research finds mica is not the cause of defective blocks

The mineral mica is not the primary cause of the failure of defective concrete blocks in Donegal homes, new international research has found.

An article in the internationally-renowned journal Cement and Concrete Research has concluded that the mineral pyrrhotite is the primary cause of crumbling blocks that has affected thousands of homes in the county.

The peer-reviewed paper outlines why mica cannot be the cause of concrete block failure in Donegal homes.  

It states that the primary failure mechanism of the concrete blocks is caused by the oxidisation of the iron sulphide mineral pyrrhotite within the concrete blocks which is releasing high levels of sulphur.  

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The research also states that the sulphur content of the aggregates used in the blocks considerably exceeds the limit value defined by the European standard for concrete aggregates.

The authors of the article, The mica crisis in Donegal, Ireland – a case of internal sulphate attack?”, say it 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 sulphate attack directly connected to the presence of pyrrhotite. They say the cause is 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 I.S.464.

The research has been published by Dr Andreas Leemann; Professor Barbara Lothenbach; Dr Beat Münch of  Empa’s Laboratory for Concrete & Asphalt, Switzerland; Professor Paul Dunlop,  School of Geography and Environmental Sciences, Ulster University; and Thomas Campbell, TA Group, Ireland.

Professor Dunlop said the new scientific evidence is important for Government officials and policymakers who are dealing with the defective concrete block crisis to ensure science-based solutions are at the heart of solutions for affected homeowners. 

 “Its publication is also timely for the NSAI who have been calling for rigorous, independently peer-reviewed scientific data for their ongoing review of IS 465,” he said. 

Professor Paul Dunlop said science-based solutions must be at the heart of solutions for affected homeowners

“In addition, it provides scientific information for the National Building Control and Market Surveillance Office, who are 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.”