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Support Figure 1. Typical arrangement for determining the water permeability of mm x mm x mm slabs made of non-absorbent material, which shall be dampened before filling with concrete.
Specimen preparation shall be started as soon as possible after sampling and, except for concrete with a prolonged workability time, completed not later than 90 Figure 2. Compacting with immersion vibrator when preparing mm x mm x mm long beams only being compacted by vibrating or rOdding, and porous lightweight aggregate concrete, only by rodding, in each case to a degree sufficient to provide a density not greater than that in the structure or structural member.
When compacting concrete containing aggregates of significantly different particle densities e. The specimens so produced shall be clearly and durably marked. Once the concrete has hardened sufficiently, usually after 16 hours.
Until testing, they may be left on the baseplate to reduce the risk of damage. Immediately after preparation, specimens for suitability and quality testing shall be stored in the mould in a closed room at a draught-free location, protected from loss of water, at a temperature of 15 to 22C preferably at 2 C.
After demoulding they shall be placed on gratings and cured in water or in a moist cabinet at 15 to 22 C preferably at 2 C. During storage in a moist cabinet, lightweight concrete specimens shall be protected against the absorption of further moisture e. Prior to testing, hardened concrete specimens shall be stored in the mould and further cured under conditions as similar as possible to those existing in the concrete intended for use in the structure.
Before the specimens are cast, the internal surface of the mould shall be thinly coated with oil, grease or release agent. Where the concrete is compacted by vibration, a collar may be fitted on the mould. The mould shall be filled with concrete to give an excess of about 20 to 30 mm above its edge after compaction. For the preparation of specimens with an hid ratio greater than 2, moulds with collar shall be vibrated during filling. Slabs used for the water permeability test shall be prepared with the mould.
Where concrete is compacted by means of an internal vibrator ct subclause 4. When preparing mm long beams, the vibrator shall be placed at an angle into the concrete at not less than four points along the long axis of the mould, and at further points in the case of longer beams cf.
The vibrator shall be immersed to a depth of approximately 20 mm above the base of the mould and left in this position until the formation of air bubbles of significant size has markedly decreased. It shall then be gradually withdrawn from the concrete so that the hole left by the vibrator closes fully without any air being entrapped.
Air-entrained concrete may only be compacted by means of an internal vibrator if this procedure is also adopted for the concrete used in the structure.
Concrete of consistence range KS may also be compacted by tamping, using a tamper as described in subclause 4.
Concrete used for the preparation of permeability test specimens is always to be compacted by vibration. Page 4 DIN Part 5 Cubes shall be placed in the testing machine so that the mould-filling direction is normal to the direction of loading, and cylinders so that the load is applied to the end faces.
The specimen shall be placed on the lower platen of the testing machine and aligned with the centre of the thrust of the machine using a centring device wherever possible. Use of packing between the specimen and the platens is not permitted. The surface of the platens shall be free from oil residues. The load shall not be applied until the upper platen of the testing machine is in full contact over its entire area with the upper surface of the specimen.
The load shall be applied steadily so as to increase the stress at a rate of O,5:I: 0. The compressive strength. After removal from the water, the specimens shall be covered with a damp cloth and stored for a maximum of one hour until testing. The volume shall be determined by measuring the specimen dimensions to an accuracy of 1 mm and the specimen mass determined to an accuracy of 20 g. The density shall be determined before applying any capping layers necessary for further testing ct subclauses 7.
From I? R,the dry density, I?