Mundic

Mundic was used from the 1690s to describe a copper ore that began to be smelted at Bristol and elsewhere in southwestern Britain. Smelting was carried out in cupolas, that is reverberatory furnaces using mineral coal.[1] For more details, see copper extraction.

Mundic once[2] referred to pyrite,[3] but has now adopted the wider meaning of concrete deterioration caused by oxidisation of pyrites within the aggregate (usually originating from mine waste). The action of water and oxygen on pyrite forms sulphate (a salt of sulphuric acid), thereby depleting the pyrite, causing loss of adhesion and physical expansion.

Mundic block problem

The Cornish word mundic is now used to describe a cause of deterioration in concrete due to the decomposition of mineral constituents within the aggregate. A typical source of such aggregates is metalliferous mine waste. Professional guidance notes describe all of Cornwall and an area within 15 km of Tavistock as being areas where routine testing for mundic is required. The notes go on to state that testing should be confined to buildings which contain concrete elements (blocks or in situ) and that were built in or prior to 1950. However, the notes contain advice that testing may be required where there are visual or other signs of mundic decay. Testing leads to a classification of A (subdivided into A1, A2 and A3), B or C. All A classifications are sound, B is sound but contains sufficient deleterious aggregate for it to be considered unstable and C is unsound. Classifications B & C mean that a property may be un-mortgagable.[4]

Typically a house is routinely screened if constructed between 1900 and 1950 from concrete block.[5]

References
  1. J. Day, 'Copper, Zinc, and brass production' in J. Day & R. F. Tylesote (eds.), The industrial Revolution in Metals (Institute of Metals, London 1991), 141.
  2. Science Direct: Very Low Frequency electromagnetic survey applied to mineralised zones on the north-western edge of Dartmoor, Devon
  3. Science Direct: ‘Mundic’-type problems: a building material catastrophe
  4. RICS guidance note, 'The Mundic Problem' (3rd Edition).
  5. Cornwall Council Mundic guide


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