In Ireland and specifically in Co. Donegal and Co. Mayo, there has been a dramatic increase in recent years in the number of properties that have been affected by the degradation of concrete blocks used in building construction due to the incorporation of deleterious quantities of pyrite, pyrrhotite and excessive mica.
Irish Standard I.S. 465:2018 + A1 2020
The Irish Standard, IS 465, has been developed for use by those who intend to provide assessment and testing services for dwellings suspected of being affected by defective concrete blocks.
The Standard states: “The reason for the widespread pattern cracking in private dwellings in Counties Donegal and Mayo is primarily due to the excessive amount of deleterious materials in the aggregate used to manufacture the concrete blocks. The deleterious material in County Donegal was primarily muscovite mica, while in County Mayo, it was primarily reactive pyrite” 1
More recently it is emerging that internal sulfate attack resulting from alteration of pyrrhotite in concrete blocks is a significant contributory factor to concrete block degradation in the Co. Donegal area of Ireland.
The Standard guides on:
- Assessing and categorising the damage
- Establishing the extent of the problem
- Identifying the scope of any testing required
- Selecting an appropriate remedial solution
I.S. 465 Testing for Pyrite and Mica in Concrete (Test Suites A, B & C)
Sandberg offers a full range of analytical and consultancy services to investigate and advise on this problem, from testing to specialist consultancy and expert witness opinion.
We provide comprehensive in-house testing in accordance with IS 465: 2018+A1: 2020, in particular, petrographic examination to UKAS-accredited standards, chemical testing and compressive strength testing supported by scanning electron microscopy, X-ray microanalysis and phase mapping to provide data for the assessment of the condition of the damaged blocks.
Sandberg has developed expertise over many years of working with organisations in Ireland and is UKAS accredited for the procedures specified in IS 465, including:
- Visual examination and measurement of cement
- Petrographic examination of thin sections for the detailed evaluation of causes of deterioration
- Classification of risk potential for future damage according to IS 465
- Measurement of free mica content by X-ray phase mapping using the scanning electron microscope
- Chemical testing for cement content, total sulfur and acid-soluble sulfate content
As an industry leader, we are directly involved with the NSAI working group responsible for the revision of I.S. 465 to take into consideration new research findings relating to internal sulfate attack and the pyrrhotite-bearing aggregates used in concrete block manufacture.
Laminated meta-argillite aggregate undergoing expansion as a result of gypsum growth
References
- Extract from I.S. 465:2018+A1:2020. Assessment, testing and categorisation of damaged buildings incorporating concrete blocks containing certain deleterious materials. ↩︎
