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Petrolab and testing your blocks

Help & AdviceReading time approx 6 min

Petrolab is one of the laboratories that tests concrete from defective block homes to the Irish Standard I.S. 465. If your engineer sends samples from your home for testing, the results may come from a lab like this. This page explains who Petrolab is, what its testing has found, and how it describes the different types of concrete.

Who is Petrolab?

Petrolab provides technical support services to the mining, minerals processing and materials industries worldwide.

  • It has been analysing rocks, minerals, ores, aggregates and concrete from all over the world for 30 years.
  • It was incorporated as a limited company in 2003.
  • In January 2009 it moved its offices and microscopy facilities to larger premises: the former Redruth Miners' Hospital building, opened in 1864, in the Cornish mining district in England.
  • It has close links with international and local companies with expertise in mining and minerals processing.

You can contact Petrolab directly to discuss testing and ask for a quote.

Is Petrolab qualified to test to I.S. 465?

Petrolab has 3 (and counting) competent concrete petrographers and 4 chartered geologists or engineers. It says this qualifies it to carry out testing to I.S. 465.

What has Petrolab found in Donegal blocks?

Over the last 10 years, a rise in noticeable cracking in homes in Donegal and the surrounding regions led to investigation into why.

Much of the aggregate used was made from metamorphosed mudstones and siltstones, including phyllite and micaceous quartzite. These produce a large amount of "free mica" (mica under 63µm in length), created when fine micas in the aggregate are worn down.

  • The loose mica frays out into the cement like confetti.
  • When the concrete is made, the mica absorbs more water. The mix becomes thicker and harder to work.
  • This is often overcompensated for by adding more water, or there is a general lack of cement.

The same phyllite and micaceous quartzite also contain the reactive sulphides pyrrhotite and marcasite. When these are exposed, they can produce acids and sulphates. That can make the aggregate expand, fracture the concrete, and break down the block itself. To read more about how this works, see where the mica narrative came from.

Petrolab has tested over 1,000 properties known to contain defective mica-bearing (and sulphide-bearing) concrete, all under the I.S. 465 testing regime.

What has Petrolab found in Mayo, Clare and Limerick blocks?

Over the last 10 years, a rise in noticeable cracking in homes in County Mayo, Clare and Limerick also led to investigation.

Here, black argillaceous limestone and calcareous mudstones were widely used to make concrete.

  • Under a microscope, these rocks show many black bands of clay.
  • In reflected light, these bands contain a large amount of small, reactive "framboidal" pyrite. The name comes from the French word framboise (raspberry), because of its raspberry-like shape.
  • Because these framboids have a large surface area for their volume, they react readily. When exposed, they produce acid and sulphates, which make the aggregate expand, fracture the concrete, and leave the blocks unfit for use.

Petrolab has tested around 500 properties known to contain defective pyrite-bearing mudstones or limestones in concrete, under the I.S. 465 testing regime.

How does Petrolab describe the risk categories?

Petrolab groups the concrete it sees into these categories. Your own report will set out the findings for your home, and your engineer can explain what they mean.

  • Negligible: less than 1% mica, a minor proportion (under 10%) of argillaceous limestone, and a total sulphur content under 1%, or under 0.1% for aggregates containing reactive pyrrhotite or framboidal pyrite.
  • Low/Medium: a broad range of aggregates containing sedimentary, igneous and metasedimentary rocks. These are commonly found in concrete as blended aggregate products or dredged gravel, so the rock types vary a great deal. They typically contain around 5% mica, varying amounts of sulphide minerals, or a mix of clean bioclastic and argillaceous limestones.
  • High (mica): typically the Donegal phyllites and micaceous quartzites, or the argillaceous black Mayo limestones. The phyllites always contain high amounts of free mica (well over 7%) and common pyrrhotite.
  • High (pyrite): the Mayo argillaceous limestones, which contain abundant reactive framboidal pyrite, commonly with high chemical sulphur values.
  • Critical: concrete that has suffered extreme degradation and is no longer sound. This is most often seen in the two main high-risk types (phyllite or black limestone), but has rarely been seen in a few other concrete types.

How many concrete types has Petrolab identified?

At an in-house training day on recognising typical I.S. 465 concrete types, Petrolab reported that it had identified around 30 types to date. Broadly, there are 6 main high-risk aggregate types and 20 low/medium-risk aggregate types, with sub-types within the main groups.

Who is Dr Chris Brough?

Dr Christopher Brough is Operations Director and co-owner of Petrolab. He has over a decade of post-doctoral experience across a wide range of mineral resource and materials projects.

His work sits where geology, engineering and materials science meet. In plain terms, he uses microscopic and chemical analysis to explain how rocks and materials behave, and turns that into practical decisions, whether improving how ore is processed or diagnosing why concrete is failing.

What does his work cover?

  • Applied mineralogy and petrology: applying mineral science to real engineering and mining problems. This includes characterising ores and geomaterials, understanding mineral make-up and texture, and linking mineralogy to processing performance and how long materials last. This fits Petrolab's wider work in automated mineralogy, petrography and materials testing for mining, construction and civil engineering.
  • Geometallurgy and resource evaluation: understanding how the minerals in an ore affect processing efficiency, metal recovery, and plant design and optimisation. He interprets mineralisation history and what it means for processing, which helps mining companies make better operational and investment decisions.
  • Environmental mineralogy: in particular acid rock drainage (ARD) and metal leaching. This means predicting how mine waste or rock will react chemically over time, which matters for environmental risk assessment, mine closure planning and regulatory compliance.
  • Construction materials and defective concrete: more recently, a significant part of his work. This covers concrete petrography, investigating defects (such as sulphate attack and deleterious aggregates) and standards-based testing, notably I.S. 465. His publications and conference work cover defective concrete (mica and pyrrhotite), risk, regulation and housing, and how materials last and fail.
  • New analytical techniques: developing and introducing new lab technology, such as automated mineralogy (SEM-EDS systems), digital petrography and imaging workflows, and new detectors for faster chemical imaging. This makes analysis faster, identifies minerals more accurately, and helps detect trace or scattered minerals.

Why does his work matter to homeowners?

His work is relevant to mining efficiency, protecting the environment from mining, and failures in housing and infrastructure, including defective concrete in Ireland and the UK.

Dr Brough presented at the Engineers Ireland seminar Deleterious Material in Concrete Masonry Units – Sharing the Knowledge on 11 April 2023. You can find the recording on our page about where the mica narrative came from.

What should I do next?

Your engineer arranges sampling and testing as part of your application. If you have questions about your test report, ask your engineer first. The step-by-step scheme guide explains where testing fits in.

Sources

  1. Petrolab: friends and partners (opens in a new tab)Petrolab · petrolab.co.uk
  2. Contact Petrolab (opens in a new tab)Petrolab · petrolab.co.uk
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