- Project plans
- Project activities
- Legislation and standards
- Industry context
- Specialist wikis
Last edited 02 Jul 2021
|View of the mundic works at Mount Morgan, circa 1905.|
The term mundic has also been adopted to describe a condition that occurs when structures deteriorate due to the oxidisation of unstable sulphides (often including pyrite), sometimes incorporated into the materials that make up concrete. Concrete is the most commonly used man-made material on earth. It is a composite material, consisting mainly of cement, water and aggregate, which can include sand, gravel or crushed rock.
- Clean: Free from any organic substances such as dust or other fine materials.
- Hard/strong: Most cement in construction is used to resist compressive forces.
- Durable: Must be able to resist forces over a long time period.
- Capable of good adhesion: The cement paste needs to physically bind to other aggregates and grip effectively.
- Good shape: Smooth and round aggregates provide good workability, whereas angular and rough aggregates tend to give better compressive strength.
One common source of aggregate is gravel or crushed rock from quarries. If that includes pyrite, the substance associated with mundic, the resulting material may produce sulphuric acid when exposed to moisture. The reaction, called sulphation, can have an impact on other materials in the concrete to form gypsum, which causes crystallisation and expansion. This can result in the deterioration of the concrete.
In the 18th and 19th centuries, Cornwall and Devon were widely mined for their rich natural resources - particularly copper and tin. As an inexpensive and plentiful substance, the mining waste material - high in pyric content - could be recycled and used in the aggregate mixture that was sometimes incorporated into concrete for construction in the early 20th century. From approximately 1900 to 1960, the practice of using this waste material in concrete for housing construction became fairly common.
Over the years, it became apparent that the integrity of concrete with pyric content could become compromised. When exposed to moisture, this material could actually erode the cement and cause the concrete to crack and make it vulnerable to even more moisture penetration, eventually causing it to crumble and fail in the most extreme instances.
 Consequences of mundic
There are certain parts of the country where mundic-containing material has been used in some residential construction (particularly in the foundation of houses) in the form of mundic blocks. In these structures, it may be necessary to subject a property to testing before it can be sold. Unless the property passes the test, it may be difficult for the potential home buyer to secure a mortgage without going to a specialist broker.
|A1, A2||No harmful materials recorded (the property will most likely be eligible for a mortgage).|
|A3 (or AC)||Questionable/passable results (the property may require additional testing).|
|B, C||Failing levels of mundic detected (a mortgage will be extremely difficult to obtain).|
|Unclassified||Initial tests are inconclusive and additional testing is necessary.|
Mundic block tests are typically conducted on residential properties in Cornwall or Devon using concrete (but not brick or stone) and built between 1900 and 1960; they will also be requested if decay caused by mundic is visibly apparent.
Reports can sometimes be transferred from one homeowner to another, but for mortgage purposes, the report must be made out in the name of the new homeowner. However, this is only possible if the original surveying firm is able to execute the transfer.
If a property receives a poor test result but the mundic block is limited to a specific part of the structure, it may be possible to replace those materials (or demolish that portion of the structure) for the property to be deemed suitable for sale. This may happen, for example, in situations where an older property (pre-1900, for instance) has had an extension added - using concrete - during a time when mundic materials might have been used. If only the extension fails the test and can be removed or rebuilt, it may be possible to secure a mortgage once the problem has been resolved.
 Related articles on Designing Buildings Wiki
- Deleterious materials in construction.
- Home ownership.
- Portland cement.
- Pyrite and mica redress issues in Dail Eireann.
- Royal Institution of Chartered Surveyors RICS.
- Types of cement.
- Types of concrete.
Featured articles and news
BSRIA explores US share of 2020 VRF market.
New fire safety requirement comes into force.
Different types of bridges are meant to move.
A logical approach to handling the internal voice of self doubt.
First fashionable in the US, decorative metal has become globally desirable.
Helping communities preserve and enhance historic environments.
Creating comfortable climates despite extreme temperatures.
Study examines how adjustable arrangements can succeed.
Government announces plans to improve accessibility.
Resource addresses pandemic-related NEC4 contract issues.
Incorporating EDI into the provision of fair access.
Government announces global innovation strategy.