ISO 1920-11:2013 download.Testing of concrete Part 11: Determination of the chloride resistance of concrete, unidirectional diffusion.
This part of Iso 1920 specIfies a method for determining the unidirectional non-steady-state chloride penetration parameters of conditioned specimens of hardened concrete. The test method enables the determination of the chloride penetration at a specified age. e.g. for ranking of concrete quality by comparative testing.
NOTE 1 The aini of the test is to assess tue potential resistance to chloride ingress for a concrete mix.
NOTI 2 Since resistance to chloride penetration depends on ageing, due to the effects of continual hydrat ion of
the concrete, the ranking may also change with age.
2 Normative references
The following referenced documents are essential for the application of this part of ISO 1920. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 1920-3, Testing of concrete — Part 3: Making and curing test specimens
ISO 1920-6, Testing of concrete — Part 6: Sampling, preparing and testing of concrete cores
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
as-cast surface
surface of a concrete element exposed in the construction works to a chloride environment
3.2
acid-soluble chloride content
amount of acid-soluble chloride expressed in percent by mass oFconcrete
3.3
chloride penetration
ingress of chlorides into concrete due to exposure to external chloride sources
NOTE 3 The exposure can be achieved by alternative methods, that are:
a) ponding the uncoated lace of the specimen in the chloride exposure solution;
b) inverting the specimen and having the uncoated face immersed in the chloride exposure solution. NOTE 4 The use of large fully immersed specimens is described in Annex C.
The standard reference solution is a 3 % by mass, sodium chloride (NaCI) solution, for an exposure period of 90 days. The solution concentration will be kept constant during the test.
NOTE 5 Other concentrations or solutions. e.g. artificial seawater, and exposure periods other than 90 days. may be set.
After the specified period of exposure, at least eight parallel layers of the chloride exposed surface are ground off the profile specimen. The acid-soluble chloride content of each layer and the average depth of the layer from the surface of the concrete exposed to the chloride solution are determined. The initial chloride content is determined by grinding a sample from the other sub-specimen and having the acid- soluble chloride content determined.
The surface chloride content c5 and the non-steady-state chloride diffusion coefficient (D55 are determined by nonlinear regression analysis using the least squares curve fitting procedure.
Because of the high coefficient of variation, approximately 15 % for D055 for the test, testing of three specimens is required and the results reported separately.
NOTE 6 The chloride diffusion coefficient varies with the age of the concrete and the period of exposure.
NOTE 7 The diffusion test described in this part of ISO 1920 is only valid for a constant initial chloride content.
NOTE 8 When precision information is available for this test, a check on the validity of the two or more results
will be introduced plus the determination of the average value.
5 Reagents and apparatus
5.1 Reagents
Reagents of analytical quality shall be used.
6 Preparation of specimens
6.1 Preparing sub-specimens
A specimen size shall be selected such that after cutting, the minimum dimension of the sub-specimens used to determine a chloride profile is at least three times the nominal maximum aggregate size. Three specimens, either cylinders, 100 mm or greater in diameter or cubes, 100 mm or greater are cast, and cured for a period of 28 days in a water filled bath with a temperature of (20 ± 2) °C, in accordance with ISO 1920-3. In hot climate locations, the curing conditions after removal of the specimen from the mould can be different from those mentioned in ISO 1920-3. In this case, the specimens may be stored in water at a temperature 01(27 ± 2) °C or in a chamber having a temperature of (27 ± 2) °C and a relative humidity of at least 95 %.
NOTE A curing period other than 28 days may be set, depending on the type of cement and purpose of the test.
After 28 days of standard curing or the specified curing period (see the above note), each cylinder or cube is cut into two sub-specimens using the water cooled diamond saw. Cylindrical specimens are cut in the direction parallel to the flat surface and cubical specimens are cut in the direction parallel to the top (trowelled) surface as shown in Figure 1. No dimension of the sub-specimens used to determine a chloride profile shall be less than three times the nominal maximum aggregate size. One sub-specimen (called the “profile specimen”) is used to determine the chloride profile, and the initial chloride sub- specimen is used to determine the initial chloride content. This initial chloride content is taken as being the chloride content of the cast concrete. The adjacent sawn faces are used to determine these values.
NOTE 2 Where a chloride profile is required that incorporates the effect of a formed surface then a formed surface from a cube specimen may be specified as the surface for chloride exposure. However, the results from such a procedure are difficult to interpret due to concentrations of cement paste and chloride at the formed surface. The use of this approach should be reported under C.lau.se.9, m), as it isa non-standard test condition.
2) Profile specimen for inversion:
After sealing in accordance with 6.2.2 and storage in the calcium hydroxide solution, the specimen shall be transferred directly to the inversion exposure apparatus without surface drying. A suitable arrangement is shown in Annex E. The volume of the exposure solution shall not be less than 125 ml per square centimetre of exposed surface.
7 Procedure
7.1 Exposure conditions
7.1.1 Chloride exposure solution
Unless specified otherwise, the chloride exposure solution shall be a 3 % NaCI solution in accordance with &1.2 a) If the chloride exposure solution is other than the reference solution [see £L2 b)J, it shall be reported. The chloride exposure solution concentration after use shall be measured and recorded.
NOTE I Where testing is related to the intended use in a specific exposure condition, the chloride exposure solution should reflect the exposure conditions taking Into account the expected depletion of chloride.
NOTE 2 During the test period the concentration of the chloride exposure solution will reduce. The volume of chloride exposure solution has been selected so that It does not have to be replaced during a test lasting 90 days. If a longer test period is required, the chloride exposure solution should be replaced at 91 day intervals.
NOTE 3 Fick’s Law is based on the assumption that the external chloride concentration remains constant during the duration of the test. In the normal test situation, the error introduced by assuming that the chloride concentration remains constant at the initial concentration Is small.
7.1.2 Exposure temperature
Where used, the temperature of the water bath for the immersion specimen, the temperature of the chloride exposure solution in the inversion method and the temperature of the chamber used to store the ponded specimen shall be maintained at (20 ± 2) °C and confirmed at least once per day and the mean and range over the duration of the test reported.
7.5 Profile grinding
After 90 days and within 8 h of removing the specimen from the exposure solution, at least eight parallel layers of the profile specimen shall be dry ground where each layer gives a sample of not less than 5 g of dry concrete, and where the outermost layer also has a thickness of not less than 1,0 mm. The thickness of the layers shall be adjusted according to the expected chloride profile so that a minimum of six points covers the profile between the exposed surface and a depth where the chloride content is above the initial chloride content. Recommended depth intervals of profile grinding for Portland cement concrete and for concretes containing fly ash, GGBS or silica fume are given in ArnwxE
NOTE 1 The values in Annex F may not be appropriate for more mature concrete or concrete taken from existing structures.
NOTE 2 In normal circumstances all seven layers would be included in the profile (the surface layer value is not included in the profile). The criterion for a minimum of six points is to prevent the whole test being made invalid if one layer is shown to be an outlier.
After grinding, keep the remainder of the profile specimen in a close fitting sealed plastic bag until the profile has been calculated. If the chloride content in the deepest layer is more than C + 0,015 %, grind off further layers so that a complete profile is established. To ensure that a complete profile has been achieved, Ic. the exposure solution has not penetrated the whole profile specimen, the last layer shall be at a depth of not less than the profile specimen thickness less 10 mm.
The concrete specimens shall be dry ground and grinding shall be performed over a surface area of at least 40 cm2 and within a boundary 10 mm inside the boundary of the contact zone to avoid edge effects and disturbances from the coating.
The profile specimen shall be securely fixed parallel to the grinder and a dust collection bag, e.g. a plastic bag, shall be fixed in position to collect the dust. Each layer should produce at least 5 g of dust. After grinding each layer, clean the equipment and profile specimen surface of any residual dust with compressed air or an air blower, then measure the depth of the layer. The depth of the layer is calculated as the mean of five evenly distributed measurements using the calliper rule.
The concretedustof each layer is collected in marked plastic bags to be analysed forchloride concentration. Each bag shall be clearly marked with the sub-specimen reference, depth interval and date.