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CONCRETE SCREENING ASSESSMENT FOR “MUNDIC” HOUSES
Why is concrete screening required?
Houses built prior to the 1950’s in Devon and Cornwall may have been built using concrete blocks using aggregates derived from mining waste. It was later realised that the sulphide minerals contained within these aggregates were potentially unstable. Sulphides may oxidise if they are exposed to damp over a long period of time. |
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Pyrite (an iron sulphide), forms a type of rust and produces sulphuric acid, which combined
with leached cement constituents, produces an expansive mineral that disintegrates the
surrounding concrete.
Concrete screening or ‘mundic testing’ (mundic being the Cornish name for pyrite), can
assess the suitability of aggregates and therefore the stability of the concrete and its
structural integrity. |
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The concrete screening service.
JGP Testing can provide a full concrete screening service in accordance with the “Mundic” Guidelines for concrete screening published in 1994 by the Royal Institute of Chartered Surveyors (R.I.C.S) and the Building Research Establishment (B.R.E), with a second edition published in 1997. These guidelines are recognised by the Council of Mortgage Lenders. |
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What assessments?
Firstly, cores are taken from selected walls and subjected to a Stage One Assessment. On completion, the property is awarded a classification.
If ‘problem’ aggregates are discovered, it is necessary then to conduct a
Stage Two Assessment. This assessment evaluates the aggregates in detail.
In a few cases where unsuitable aggregates have been identified, but the concrete appears ‘sound’, then a Stage Three Assessment can be conducted which simulates weathering of the concrete and can provide an indication of its long term stability.
The client is always contacted before a Stage Two or Stage Three Assessment is conducted.
For further information on all stages of Mundic Testing, please contact email address
post@johngrimes.co.uk |
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