AS 1012.8.4:2015 – Methods of testing concrete Method 8.4: Method for making and curing concrete-Drying shrinkage specimens prepared in the field or in the laboratory.
(b) The number of tamping strokes per layer required to produce adequate compaction will vary according to the type of concrete used. The total number of tamping strokes per layer shall be not less than 35.
(c) As the top layer of concrete is being placed, ensure that the concrete around the gauge studs is adequately compacted. Take care not to loosen the gauge studs.
(d) Close any holes remaining in the surface of each layer by lightly tapping the sides of the mould with the mallet.
(e) Slightly overfill the top layer of the mould. After the top layer has been compacted, strike off and smooth the surface of the concrete with a wooden float.
6.2.3 Compaction by vibration
The procedure for the compaction of specimens by vibration is as follows:
(a) Fill the moulds in two approximately equal layers. Rigidly attach the mould to the vibrating table.
(b) Vibrate each layer until the surface becomes relatively smooth in appearance. Do not prolong vibration beyond the point at which mortar commences to collect on the surface.
(c) After the top layer has been compacted, strike off and smooth the surface of the concrete with a wooden float.
6.2.4 Compaction of self-compacting concrete
The procedure for compaction of specimens with self-compacting concrete is as follows:
(a) Place concrete in the mould using a scoop, ensuring symmetrical distribution of the concrete within the mould.
(b) Tap the mould with the mallet until all entrapped air is removed.
(c) Strike off and smooth the surface of the concrete with a wooden float.
6.3 Curing of specimens
6.3. 1 Initial curing in moulds General
Immediately after the test specimen has been moulded, place the mould containing the specimen in the initial curing environment and loosen the gauge stud holder retaining screws so as to prevent restraint of the gauge stud in case of shrinkage of the concrete during initial curing.
6.3. 1 .2 Initial curing under standard conditions
Store the specimens in a saturated condition (minimum 95% relative humidity), undisturbed in their moulds on a rigid horizontal surface in air at the following temperatures until demoulded:
(a) Standard temperate zone 23 ±2°C.
( b) Standard tropical zone 27 ±2°C.
I The standard temperature zones referred to above are as specified in AS 10 12.8.1.
2 Saturated conditions can be maintained either by moisture retaining covers applied to the moulds, or by placing specimens in a humidity controlled environment. Storage of specimens in the field
In the field, store specimens for a period of not less than 1 8 h from moulding, nor more than 24 h as follows:
(a) In a covered location adjacent to the moulding site, preferably indoors and protected from wind and extremes of temperature.
(b) Undisturbed in their moulds on a rigid horizontal surface, with lids fitted so as to prevent the loss of moisture from the specimen.
NOTE: The aim is to provide conditions for test specimens which give a maximum of protection
from extremes of temperatures and loss of moisture during their storage in the field. 6.3. 1 .4 Non —compliance with initial curing conditions
When standard moist-curing does not commence within 27 h of moulding, the test results shall be liable to rejection. Under these circumstances the following data shall be recorded:
(a) The reason for the delay.
(b) The length of time between moulding and commencement of standard moist-curing.
(c) The ambient maximum and minimum temperatures in the locality of the curing.
NOTE: Unless otherwise specified, the temperatures from the nearest Bureau of Meteorology weather station are adequate.
6.3. 1 .5 Initial curing under non—standard conditions
As soon as is practicable after a period of 1 8 h from moulding, transport specimens stored under non-standard conditions shall be transported to the laboratory for dernoulding, such that they are placed under standard moist curing conditions within 24 Ii of moulding.
6.3.2 Demoulding of specimens General.