Mundic and Building Services
Cornwall and parts of Devon have seen centuries of extensive mining activity. Between 1900 and around 1965, mine waste was widely used as a low cost and readily available aggregate, one that builders and blockmakers did not anticipate would cause potential long term problems.
Minerals commonly found in mine waste, such as pyrite (or mundic as it is also known), can decay over time and cause a slow chemical reaction which can result in concrete deterioration. This can lead to powdering and crumbling, and can cause weakening of a mass of concrete and mortar, and even structural failure in rare cases. Building materials containing mundic were also transported and used outside mining areas. Blocks containing mundic were mixed with other blocks, and now appear across housing estates and sometimes in patches within individual properties, small developments or extensions.
Today, mortgage lenders require assurance that a property will remain sound for the period of the loan. Property buyers also need to know that the property is mortgageable. Our mundic block testing service can involve up to three stages, if necessary, and is undertaken under the supervision of a chartered surveyor. Our tests predict the potential behaviour of concrete over time when assessing properties and making recommendations to lenders.
What Is A Mundic Test?
A greater understanding of the substances which can cause the mundic problem has enabled tests to be developed which are capable of detecting mundic in the samples analysed.
The current procedure and tests have been developed over the past twenty years following research and input primarily from the Cornwall and Devon branch of the Royal Institution of Chartered Surveyors, the Building Research Establishment in London, and the Camborne School of Mines with its unique knowledge of the geology of the area.
The guidance on procedures and tests officially published in 1994 and updated in 2015 by the RICS/BRE have now been widely adopted as the current best practice and are acknowledged as such by the Council of Mortgage Lenders.
What Does A Mundic Survey Involve?
The test requires the collection of, on average, 6-10 representative core samples of concrete from the structural fabric of the property. Each sample needs to be 50mm (2”) in diameter. The cores are obtained by hand held drilling using a diamond tipped core drill. This method involves minimum disruption and makes the repair of the sample points simple, quick and effective.
In order to ensure a reliable result, the appropriate selection of sample points is essential, and are likely to include all accessible walls, extension walling and foundations. The samples are bagged and sent to our laboratory for petrographic analysis.
All sample drill holes are repaired and made good prior to the sampler leaving the property. The sampling process is always carried out in the presence of a Chartered Building Surveyor.
What Does The Mundic Test Do?
By analysing samples of concrete taken from the property by various methods the presence of substances known to cause problems can be confirmed. The analysis process is as follows;
Stage One, involves detailed examination of core samples under a low power microscope. To a trained petrographer, identification of the aggregate type can be made from this inspection and, in the majority of cases, a classification for the concrete can be determined.
It must be stressed that approximately 75% of properties tested will pass the Stage One analysis, receiving a Group A classification.
Stage Two analysis involves the core sample being cut into wafer-thin segments for a further examination under a high power microscope and possibly subjected to a range of ancillary analytical techniques. Stage Two analysis is not included in the initial Stage 1 cost and is only carried out if a Stage 1 test is inconclusive.
Stage Three involves the sample being subjected to an accelerated weathering test under environmentally controlled conditions in an attempt to activate a reaction between the aggregate and cement binder. The test takes place over several months.
What Will The Report Provide?
The Stage One report will consist of the surveyor’s written interpretation of the petrographic analysis results, and will classify the property according to the *RICS/BRE guidance note recommendations. The classification will be explained fully in the surveyor’s report. If the samples are affected, the report will also provide some indication of the extent of the effect on the lifespan and value of the property and will, if deemed necessary, recommend appropriate further action, normally that a Stage Two analysis be carried out.
In some cases, properties referred for a Stage Two test will then achieve a satisfactory result.
What Do We Offer?
If you require Mundic block testing we can recommend a Chartered Building Surveyor and will carry out the analysis on the surveyors behalf.
Wheal Jane Consultancy offer analytical petrographic services to Chartered Building Surveyors. We can undertake all stages of Mundic testing.