BS/EN 12350-7-2019 pdf download.Testing fresh concrete Part 7 : Air content-Pressure methods.
5.2.1 Sampling
Obtain the sample of fresh concrete in accordance with EN 12350-1. Remix the sample before carrying out the test.
5.2.2 Filling the air test container and compacting the concrete
Clean the air test container and dampen with the moist cloth immediately prior to starting the test.
Using the scoop, place the concrete in the air test container in such a way as to remove as much entrapped air as possible.
Depending on the consistence of the concrete and the method of compaction, the air test container shall be filled in as many layers as necessary to achieve full compaction by using one of the methods described in 5.2.3 or 5.2.4. In the case of self-compacting concrete, the air test container shall be filled in one operation and no compaction shall be applied during air test container filling or after the air test container is filled.
NOTE 1 Full compaction Is achieved using mechanical vibration, when there Is no further appearance of large air bubbles on the surface of the concrete and the sur1ce becomes relatively smooth with a glazed appearance, without excessive segregation.
NOTE 2 The number of strokes per layer required to produce full compaction by hand will depend upon the consistence of the concrete.
Further guidance on methods of compaction for concretes having different consistencies or cast in different sizes of moulds may be given in provisions in the place of use of the concrete.
The quantity of material used in the final layer shall be sufficient to fill the air test container without having to remove excess material. A small quantity of additional concrete may be added if necessary and further compacted in order to fill the air test container, but the removal of excess material should be avoided.
5.2.3 Mechanical vibration
5.2.3.1 Compacting with internal vibrator
Apply the vibration for the minimum duration necessary to achieve full compaction of the concrete. Avoid over- vibration, which may cause loss of entrained air.
Care should be taken not to damage the air test container. The vibrator should be vertical and not allowed to touch the bottom or sides of the air test container. The use of a filling frame is recommended.
NOTE Laboratory tests have shown that great care is needed if loss of entrained air Is to be avoided, when using an Internal vibrator.
5.2.3.2 Compacting with vibrating table
Apply the vibration for the minimum duration necessary to achieve full compaction of the concrete. The air test container should preferably be attached to, or firmly held against, the table. Avoid over- vibration, which may cause loss of entrained air.
5.2.4 Compacting by hand with compacting rod or bar
Distribute the strokes of the compacting rod, or bar, in a uniform manner over the cross-section of the air test container. Ensure that the compacting rod, or bar, does not forcibly strike the bottom of the air test container when compacting the first layer, nor penetrate significantly any previous layer. Subject the concrete to at least 25 strokes per layer. In order to remove pockets of entrapped air but not the entrained air, after compaction of each layer, tap the sides of the air test container smartly with the mallet until large bubbles of air cease to appear on the surface and depressions left by the compacting rod or bar, are removed.
5.2.5 Measuring air content
After the concrete has been compacted, strike off level with the top of the air test container using the compacting rod, and smooth the surface with the trowel.
Thoroughly clean the flanges of the air test container and cover assembly. In the absence of the spray tube, place the deflecting plate centrally on the concrete and press it into contact. Clamp the cover assembly in place. Ensure that there is a good pressure seal between the cover and the air test container. Fill the apparatus with water and tap lightly with the mallet to remove air adhering to the interior surfaces of the cover. Bring the level of water in the standpipe to zero by bleeding through the bleed valve with the air vent open. Close the air Vent and apply the operating pressure, P. by means of the air pump. Record the reading on the gauge tube, h1, and release the pressure. Read the gauge tube again and if the reading, h2, is 0,2 % air content or less record the value (h1 — h2) as the apparent percentage air content, A1, to the nearest 0,1 % air content. If h2 Is greater than 0,2 % air content apply the operating pressure, P. again, giving a gauge tube reading h3 and a final reading h4 after release of the pressure. If (h4 — h2) is 0,1 % air content or less record the value (h3 — h1) as the apparent percentage air content. If (h4 — h2) is greater than 0,1 % air content, it is probable that leakage is occurring and the test shall be disregarded.
6 Pressure gauge method
6.1 Common apparatus for fresh concrete testing
The apparatus listed below for the execution of this test method shall be in accordance with the specification given EN 12350-1 and as specified below.BS/EN 12350-7-2019 pdf download.
BS/EN 12350-7-2019 pdf download
PS:Thank you for your support!
