BS EN 12390-12:2020 pdf download.Testing hardened concrete Part 12: Determination of the carbonation resistance of concrete一Accelerated carbonation method.
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 1 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 [5] 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 he 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 volume of the target value during 96 % of the storage time in the carbonation chamber
Apparatus for recording the relative humidity with a maximum permissible measurement error of ± 3,0 % and the temperature with a maximLim permissible measurement error of ± 0,5 °C.
Apparatus for recording CO2 concentration with a maximum permissible measurement error of ± 0,1 % by volume.
NOTE 5 The recording apparatus can be fitted with an audio/visual/email or other suitable alarm to alert breaches of CO2 concentration within the storage chamber due to possible apparatus malfunction.
The accuracy of the sensors shall be higher than the requirements for the CO2 and humidity content measurements. The CO2 and humidity sensors shall be controlled and calibrated regularly
Fans to facilitate steady circulation of air within the storage chamber.
6 Production of concrete specimens
6.1 General
Representative samples of the constituents, e.g. iemtnt, aggregates, shall be used for making the test specimens. Either a sample of concrete is taken from the concrete production plant or the concrete mixes shall be produced using the laboratory’s standard procedures. The specimens for 1 test shall be cast from a single batch of concrete.
NOTE A minimum batch volume of 50 I is sufficient.
Where the specimens are prepared by the client or their representative, the test laboratory shall be informed of the day of casting and a confirmation that the specimens were stored as required by this document.
Each test shall comprise at least 2 prismatic beams each being at least 280 mm long and the designated sized, according to EN 12390-1, shall be at least 3 times the maximum aggregate size or 2 cubes per test age with a side length of at least 3 times the maximum aggregate size. Prismatic beams with designated size d of 100 mm are the reference specimens.
Avoid or minimize the use of mould release agents on the moulds as they may influence the carbonation depth.
6.2 Making and testing concrete specimens
Measure the consistence class or target value using EN 12350-2. EN 12350-3, EN 12350-4 or EN 12350- 5 as appropriate and record the value. If a self-compacting concrete is specified, measure and record the specified properties of the fresh concrete using the appropriate test methods. For each mix, cast 2 prisms or 8 cubes or 5 concrete cylinders from a single batch of concrete. Cast the prisms horizontally in accordance with EN 12390-2. After finishing the prisms/cubes/cylinders, cover the exposed surface with polythene or similar impermeable sheeting to prevent drying. After 20 ± 4 h, the moulds shall be stripped and the prisms/cubes/cylinders stored in accordance with EN 12390-2.
It is recommended that in addition to the test specimens for quantifying carbonation resistance at least
2 compressive strength specimens are made and tested in accordance with EN 12 390-3 at 28 days. Where
a number of mixes are made, additional testing. e.g. the 28 day strength, should be undertaken to confirm
consistent manufacture, or identiI’ anomalous batches where mixes may need to be repeated.
After removal from the curing tank, the specimens shall be immediately wrapped and sealed in polythene or similar material that will prevent drying during transportation. Alternatively, they should be transported whilst remaining fully immersed in water e.g. in a mobile curing tank On arrival at the test laboratory, the test specimens shall be unwrapped, checked for damage and then stored in accordance with EN 12390-2 until they are 28 days old.BS EN 12390-12 pdf download.