ISO 679:2009 pdf free download – Cement一Test methods一 Determination of strength.
The three vertical planes through the axes of the three rollers shall be parallel and shall remain parallel, equidistant and normal to the direction of the specimen under test. One of the supporting rollers and the loading roller shall be capable of tilting slightly to allow a uniform distribution of the load over the width of the specimen without subjecting it to any torsional stresses.
4.6.6 Compressive strength testing machine, for determining the compressive strength, of suitable capacity for the test (see paragraph 8 of this subclause), with an accuracy of 1,0 % of the recorded load in the upper four-fifths of the range being used when verified in accordance with ISO 7500-1.
It shall provide a rate of load increase of (2 400 ± 200) N/s. It shall be fitted with an indicating device that shall be so constructed that the value indicated at failure of the specimen remains indicated after the testing machine is unloaded. This can be achieved by the use of a maximum indicator on a pressure gauge or a memory on a digital display. Manually operated testing machines shall be fitted with a pacing device to facilitate the control of the load increase.
The vertical axis of the ram shall coincide with the vertical axis of the machine and, during loading, the direction of movement of the ram shall be along the vertical axis of the machine. Furthermore, the resultant of the forces shall pass through the centre of the specimen. The surface of the lower machine platen shall be normal to the axis of the machine and remain normal during loading.
5.1.3 Iso standard sand
ISO standard sand shall comply with the particle size distribution specified in 5.1.2 as determined by sieve analysis on a representative sample of sand of total mass not less than 1 345 g. Sieving shall be continued until the amount of sand passing through each sieve is less than 0,5 g/min.
The moisture content shall be less than 0,2 %, determined as the loss of mass of a representative sample of sand after drying at 105 °C to 110 °C to constant mass and expressed as a percent mass fraction of the dried sample.
During production, these determinations shall be carried out at least once a day. These requirements are insufficient to ensure that the ISO standard sand gives equivalent performance to the ISO reference sand. Such equivalence shall be initiated and maintained by the validation testing described in Clause 11.
ISO standard sand shall be pre-packed in bags with a content of (1 350 ± 5) g; the type of material used for the bags shall have no effect on the results of the strength testing, and the contents of each bag shall comply with the particle size distribution specified in 5.1.2.
ISO standard sand should be carefully stored to prevent damage or contamination, particularly with moisture, prior to use.
6 Preparation of mortar
6.1 Composition of mortar
The proportions by mass shall be one part of the cement (5.2), three parts of ISO standard sand (5.1), and one-half part of water (5.3) (water/cement ratio 0,50).
A batch, for three test specimens, shall consist of (450 ± 2) g of cement, (1 350 ± 5) g of sand and (225 ± 1) g of water.
6.2 Mixing of mortar
Weigh the cement and water by means of the balance (4.6.8). When water is added by volume, it shall be dispensed with an accuracy of ± 1 ml. Mix each batch of mortar mechanically using the mixer (4.6.2). The timing of the various mixing stages refers to the times at which mixer power is switched on/off and shall be maintained to within ± 2 s.