ISO 1920-4-2020 pdf free.Testing of concrete — Strength of hardened concrete.
Specimens that are badly honeycombed and cracked shall not be regarded as being representative ofthe quality of concrete supplied.In general, standard cube and cylinder specimens should not be testedif they are badly honeycombed as this is an indication of poor specimen making.When such specimensare tested, the test report shall include the fact that the specimen was honeycombed.
Where the designated size, lf or l, of the cross-section is outside the tolerances, the specimens may beused for testing by using the actual dimensions; see 4.6.Where the dimensions or shape of a test specimen exceed the respective tolerances given in ISO 1920-3,the specimen shall be rejected or adjusted (if feasible) by one or more of the following methods:
– uneven surfaces levelled by grinding or by capping;
– the deviation of angles corrected by cutting and/or grinding.The procedures given in Annex B shall be used to adjust the specimen.Adjustment by grinding shall be the reference method.
The test shall be carried out using the following:
A compression-testing machine, robust,related to the size of specimen and capable ofproviding the rate of loading with minimum desired specifications as mentioned in 4.5.1 and 4.5.2. Itshall be in calibration at the time of test. The calibration shall be carried out at least once per year.
Accuracy of the test machine shall be such that the percentage error for the loads within proposedrange of use of the machine and shall not exceed ±1,0 % of the indicated load.
The compression testing machine shall be provided with a control system. The control system maybe operated either by manual or automatic means. If the machine is not equipped with automaticapplication of force, a pacer shall be fitted to enable the operator to maintain the specified rate. Thepacer shall indicate a rate within ±5,0 % of the specified rate.ISO 1920 pdf download.