Mundic Test (Concrete Screening Test)
What is Mundic? In the early part of this century, mining spoil and waste was used as a source of aggregate for concrete in the south-west of England. In some instances the minerals (including pyrite, or ‘mundic’) have reacted to weathering; this leads to deterioration in the physical strength of the concrete.
Mundic Test
Properties were constructed using the suspect aggregate across the Devon and Cornwall area, in particular between 1907 and 1965.
Mundic Test
The phenomenon is commonly known as the ‘mundic’ problem, or ‘concrete cancer’.
Mundic tets are usually required only for between 1907 and 1965.
The Royal Institution of Chartered Surveyors (RICS) issues the current guidelines for dealing with mundic properties, and it is these guidelines that property professionals use when assessing properties and making recommendations.
- Stage 1 analysis is carried out in our own laboratory at Wheal Jane Mine. Further testing, such as Dry Density testing, is also carried out in house.
- Stage 2 analysis which entails a detailed petrographic study of a single prepared ‘thin section’ of core
- Stage 3 analysis - wetting expansion - is carried out in our own laboratory at Wheal Jane Mine.
Stage 3 Expansion test for ‘Mundic’, or Moisture Sensitivity Testing:
It has been noted that some Class B concretes had a much better structural ‘life’ than others, and so a test was devised to differentiate between the two. The purpose of the new test is to release some Class B properties back on to the mortgage market by re-classifying them as Class AB. In January of 2002 RICS issued a supplement to the 2nd Edition of the Guidance Notes, outlining a new test available for classifying mundic concrete.
Stage 3 procedure
In brief, the test takes four samples of Class B concrete from a property and places them in sealed containers to keep them in a humid and warm (38°C) environment for some 250 days. The core expands during this time as it takes in moisture and this expansion is recorded every month by means of measuring the distance between 6 studs placed around and along each core.
A fifth sample is set aside for petrographic analysis.
The expansion of the core is expressed as a percentage and compared with set targets. If the average expansion of any one set of cores is less than 0.025%, and no single set of studs on a core exceeds 0.04% expansion, the concrete can be re-classified as Class AB.
The Cores
The cores submitted for testing must all be of the same type of concrete. Properties with more than one type of Class B concrete will require a set of cores for each type of concrete. The five cores have very specific parameters:
- must be at least 70mm in length (excluding render)
- a nominal 75mm in diameter
- no mortar joints
- in good condition, i.e. not cracked
- must be passed by the petrographer as suitable for testing
We would recommend that, where possible, any render/plaster be removed from the subject wall prior to taking cores. This helps in two ways: firstly it allows the sampler to avoid mortar joints and secondly the removal of render from the concrete is easier in a section of wall than from a core (the cores used for testing must have their render removed).
The Cost
The costs involved are a combination of laboratory fees and the surveyor’s fees. Our laboratory charge is £750 (plus VAT) per set of four samples.
Costs for multiple sets of samples from the same property can be negotiated. The laboratory charge covers set up, 7 day wetting expansion and the first 7 day measurements. As the test progresses, monthly fees apply.
Our rate is very competitive, despite a substantial investment into setting up a Stage 3 testing facility. Our laboratory uses a dedicated Weiss-Gallencamp Environmental Chamber, which is capable of the very high accuracy and reliability required for this kind of testing.
Core expansion measurements are made using a Demec Mechanical Strain Gauge with an accuracy of 0.002mm.
A report is issued at the end of testing, complete with a graph showing the performance of the cores against the recommended expansion levels.
If you have any questions regarding mundic testing, please do not hesitate to contact us.
Note. The above is only a summary of the detailed document. The new supplement is available in full from the RICS, ISBN 1-84219-082-2.
For a free quotation or an answer to any mundic queries, please contact us.
