Engineers investigating the mica crisis that is expected to cost the State billions of euro have “been looking for the wrong thing for years”, an international expert has warned.
In advance of a conference in Co Donegal – the county worst affected by homes crumbling as a result of defective concrete blocks – Dr Andreas Leemann said it is “very disturbing” the chief problem is not mica, a component in blocks long blamed for the scandal.
Dr Leemann, a leading international research scientist at the Swiss Federal Laboratories for Material Science and Technology (EMPA), has been analysing samples from affected homes for the past year.
Speaking in advance of the conference, he said the high presence of another iron sulphide in the defective blocks known as pyrrhotite is causing the damage to thousands of houses.
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“It is not a mica problem, it is pyrrhotite,” he said. “[Engineers] have been looking at the wrong thing for years.”
Dr Leemann, at the invitation of Prof Paul Dunlop at the University of Ulster, has been analysing defective concrete blocks from four affected homes in Co Donegal, which he said are “typical” of those crumbling.
His microscopal laboratory testing made “very clear” there is “pyrrhotite oxidation” occurring in the cement – which acts as the “glue” for the blocks – which then releases a sulphur.
“The reaction can be wide and different,” he said. “In the first phase, it leads to expansion, stress and cracking ... the second phase is strength loss. All the scientific evidence so far indicates we have an internal problem which is triggered by pyrrhotite oxidation.”
According to Dr Leemann, Irish regulations for determining whether a building has been damaged by defective concrete blocks – IS 465, a 46-page guideline for the so-called mica crisis by the National Standards Authority of Ireland – “does not say anything about pyrrhotite”.
“This is very disturbing ... basically the point is they have been looking for the wrong thing for years,” he said. “There is no other scientific evidence other than internal sulphate attack with pyrrhotite oxidation.”
While mica might have a “certain influence” it is “surely not what it is claimed to be”, he said.
Tests on affected homes “might record whether there is pyrrhotite there or not, but they don’t have particle particulate weight on it”, he added.
European Union standards set down in 2002 “clearly state” if pyrrhotite is present in blocks then it has to be weighted against the content of sulphur, Dr Leemann said.
“We have tested the sulphur content of these four houses. The values [of sulphur] exceeded the [EU] limits by a factor of four to seven,” he said. “In principle, the aggregates are not according to European standards. You could even say they are a violation of European standards on concrete aggregates.”
Dr Leemann said his own findings on the “typical” four homes is backed up by a wider study of 91 houses where “the majority contain an appreciable amount of pyrrhotite”.
Claims that frost was a key factor in the crumbling of defective blocks “lack any scientific basis”, he added, pointing to a proportion of houses with cracks developing in the inner walls. Frost damage also “looks completely different” to cracks evident in affected homes.
As a result of a “political decision” there is an assumption that the foundations of affected homes “are fine”, but “we don’t know this ... it could be that they also have the same problem from internal sulphate attack”, he said. “We need more research on this.
“I wouldn’t say by default that every house has to be demolished, but we have to gain more knowledge for making these decisions. It has to be based on fact not assumption as has been the case, Dr Leemann said. “For me, it is a mystery why there has not been a major research programme on this started years ago. It gives me the feeling that people didn’t want to know.”
Dr Leemann is presenting his findings at the conference on The Science and Societal Impacts of Defective Concrete in Letterkenny on Tuesday, organised by academics at University of Ulster and the Atlantic Technological University.
Dr Leemann said existing tests on affected houses - thousands of which have been carried out - may show a low mica content, which homeowners could believe means they have no problem.
“But they may have a high iron sulphide content. They think it is fine, but that could be creating a future problem,” he added.
Among those expected to speak at the gathering are John O’Connor, appointed by Minister for Housing Darragh O’Brien as a homeowner liaison officer for affected families; Damien Owens of Engineers Ireland; and Martin McDermott, chairman of the defective blocks steering committee at Donegal County Council.
Professor Dunlop, research director for geography and environmental science at Ulster University, said the entire Government redress scheme is underpinned by the standard IS465, which doesn’t mention pyrrhotite.
“IS465 needs to catch up - if it doesn’t, then all homeowners are going to be getting is the wrong decision making,” he said. “At the moment, reports (on affected houses) only have to assess them for mica for the scheme.
“It is like going to the GP for a sore leg, and he just feels it, says he thinks he might be bruised when really you need an MRI scan to know what is really going on.
“You could have low mica content on your report and think you are fine. You could have a large amount of pyrrhotite and that will destroy your concrete - it doesn’t matter what the mica is doing.”
Potentially, some of the tests done to date are “useless”, he added.
“Engineers are being forced to make decisions on incomplete information, based on a mica problem. As the pyrrhotite issue comes to fore, engineers are left in a very difficult situation, for example, to recommend replacing the outer leaf (of a house) only, while inside could be full of pyrrhotite which will potentially oxidise further down line and cause problems then. It is madness.”
The chances of a house crumbling because of undiagnosed iron sulphides problems is “quite high”, Prof Dunlop said.
“Anybody who has had their homes tested for defective concrete issues, needs to go back and look at the iron sulphide content in the report, particularly pyrrhotite, which is very prevalent.
“It is one of the highest reactive iron sulphides we have. The sulphur turns into sulfuric acid, and once you have that in the cement it doesn’t work very well. The cement is attacked by the sulfuric acid, causing swelling and cracking.
“This explains the phenomenon we see on the ground in Donegal.”
The Government also needs to make a “massive injection” in research funding to understand the root cause of the crisis, he added.
“What has happened in Ireland is the Government came up with a scheme to remediate homes without fully understanding the failure mechanism in the concrete. That is a backwards way of doing anything.”