BS EN 12390-12-2020 Testing hardened concrete Part 12: Determination of the carbonation resistance of concrete – Accelerated carbonation method

BS EN 12390-12-2020 Testing hardened concrete Part 12: Determination of the carbonation resistance of concrete – Accelerated carbonation method. 5 Reagents and apparatus A solution of 0.8 g of phenolphthalein powder dissolved in a solution of 70 ml ethanol and 30 ml of deionised water or a suitable alternative indicator giving a colour change in the range pH 8 to 11 that gives a sufficiently clear colour change in concrete to differentiate the neutralized zone, e.g. thymolphthalein3. WARNING — Phenolphthalein is listed in REACH appendix 2 and its lists of substances of very high concern. Phenolphthalein powder should be handled with the greatest care using safety gloves in a fume cupboard fitted with an extractor. Where needed, a fixing solution to permanently fix the colour change in the concrete specimen, see Clause 7. NOTE I Suppliers of some indicator solutions also provide a fixing solution that permanently fixes the colour change. A magnifier and a gauge with a precision of 0,5 mm. A storage chamber with a carbon dioxide concentration within the storage chamber in percent by volume as indicated in Clause 4, temperature at (20 ± 2) °C and a relative humidity at (57 ± 3) %, see Annex A (informative) for details of a suitable chamber. The carbon dioxide concentration shall be within ± 0.5 % by volume of the target value with no variation for longer than 4 h outside the target value ± 1,0 %. NOTE 2 Experience (51 has shown that if saturated surface-dry specimens are placed in the storage chamber shortly after removal from water curing, the relative humidity can exceed that permitted. Also, without active control of the carbon dioxide concentration, the levels can drop below the permitted tolerance as the carbonation process continues. Therefore, it is important that the storage chamber has active control on carbon dioxide concentration, relative humidity and temperature. NOTE 3 Relative humidity levels can be maintained using methods at the discretion of the laboratory, for example active humidification/dehumidification. NOTE 4 When the door of the storage chamber is opened, the carbon dioxide concentration within the chamber can fall rapidly, and therefore, for practical reasons, a short period of low carbon dioxide concentration is acceptable. The cumulative periods of times of low carbon dioxide concentration cannot exceed 4% of the storage time of 63 days. The relative carbon dioxide concentration Is expected to be within ± 0,1 % by...