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 pdf free.Testing hardened concrete Part 12: Determination of the carbonation resistance of concrete – Accelerated carbonation method.
This document quantifies the carbonation resistance of concrete using test conditions that accelerate the rate of carbonation. After a period of preconditioning. the test is carried out under controlled exposure conditions using an increased level of carbon dioxide.
NOTE The test performed under reference conditions takes a minimum of 112 days comprising a minimum age of the specimen prior to curing under water of 28 days, a minimum preconditioning period of 14 days and an exposure period to increased carbon dioxide levels of 70 days.
This procedure is not a method for the determination of carbonation depths in existing concrete structures.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
EN 12350-2, Testing fresh concrete — Part 2: Slump test
EN 12350-3, Testing fresh concrete — Part 3: Vebe test
EN 12350-4, Testing fresh concrete — Part 4: Degree ofcompactabthty
EN 1 2350-5, Testing fresh concrete — PartS: Flow table test
EN 12390-2, Testing hardened concrete — Part 2: Making and curing specimens forst rength tests
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://wwwelectropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
3.1 carbonation rate
average rate at which the carbonation front penetrates concrete expressed as mm/’/(days)
Note I to entry: The carbonation rate will vary depending upon the test curing. preconditioning or exposure conditions and therefore any carbonation rate has to be qualified by the conditions under which it was obtained. The abbreviation KAC’ is the carbonation rate under the test conditions specified in this document.
3.2 depth of carbonation
depth as measured using a phenolphthalein solution or an alternative indicator that results in a colour change in the range of pH 8 to pH 11 on the freshly-split concrete surface
3.3 effective time
time in days spent in the storage chamber with the concrete specimens continually exposed to carbon dioxide
3.4 mean carbonation depth
dk mean depth of carbonation of two specimens
3.5 single point carbonation depth
dk, point depth of carbonation recorded for a single point on a specimen
Note 1 to entry: This is the measured depth of carbonation except where the measurement point coincides with
a dense particle, porous particle or void, see 8.3 and 8.4.
3.6 specimen carbonation depth
dk, spec mean depth of carbonation of a single specimen
3.7 specimen face carbonation depth
dk face
mean depth of carbonation of a single exposed face of a single specimen
4 Principle
2 concrete prisms, 8 concrete cubes or 5 concrete cylinders are cast and thereupon cured for 28 days in accordance with EN 12390-2. The test specimens are then conditioned in a laboratory air environment for 14 days and then placed in a storage chamber with a carbon dioxide concentration within the storage chamber in percent by volume of (3,0 ± 0,5) % when the storage chamber is at normal conditions (1 013 mbar at 25°C) 2, temperature (20 ± 2) °C and relative humidity (57 ± 3) % for periods of up to 70 days. Immediately prior to placing specimens in the storage chamber and after prescribed ages corresponding to 7, 28 and 70 days of storage in the chamber (this gives approximately equidistant values of/days), 2 of the cubes are split in half; 1 cylinder is split in half along its vertical axis and a 50 mm slice is split from each of the prisms and the depths of carbonation measured.
On one half of each cylinder or each slice of prism or on one half of each cube, twelve single point carbonation depths (dkp0j1t) are measured after each exposure period and the depth of carbonation dk, at that exposure time is expressed as the mean of the two test specimens. Using measurements taken at the fixed times, the carbonation rate expressed as mm/Idays is deterniined.
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 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 j5J 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 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 maximum permissible measurement error of ± 0,5 °C.
Apparatus for recording the relative humidity with a maximum permissible measurement error of ± 3,0 % and the temperature with a maximum 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.BS EN 12390-12:2020 Testing hardened concrete Part 12: Determination of the carbonation resistance of concrete – Accelerated carbonation method