ISO 18650-2:2014 pdf free
ISO 18650-2:2014 pdf free.Building construction machinery and equipment – Concrete mixers
The design and execution of the whole structure of the mixer and its components, such as the mixing chamber (drum, pan, or trough), rotor with blades or paddle agitator(s), their directions of rotation,charging and discharging devices (if any), should be verified according to the manufacturer ‘s instructions.
It shall be determined that the number of revolutions per minute of a drum or mixing tools conforms to the manufacturer’s specification.
The drive system should be able to restart 5 min after being stopped when the mixer has completed the mixing of the test batch as specified in 5.2.
NOTE 1 The “restart” is for the additional mixing and does not warrant a series of restarts for the next batches.The mixer shall be discharged according to its design or as specified by the manufacturer The closure of the mixing chamber shall be so designed that the loss of the mix before discharge, i.e. during charging and mixing, remains below 0,5 %.
NOTE 2 The “below 0,5%”does not apply to the 1st batch which has more adhesion of mortar to the inner wall of drum.
The mixing efficiency is determined by the uniformity of the concrete mix and the compressive strength of the concrete cubes or cylinders, sampled after mixing time. The determination of the uniformity of the concrete mix includes the following variance tests on the sampled specimens:
a) air content;
b) content of mortar per unit volume;
c) content of coarse aggregate per unit volume;
d) consistency (slump).
The values of the concrete-mix component content (air, mortar, coarse aggregate), determined as the test results, as well as the consistency and compressive strength, are subsequently used for calculation of their variances.
Two portions of the concrete mix are sampled directly from the mixing chamber immediately after ensured mixing time (see Figures 2, 3, 4 and 5). Where the direct sampling from inside the mixing chamber is difficult, the sampling may be done from the concrete mix discharged to the hopper (see Figures 6 and 7). The volume of the sample (portion) should be a minimum of 20 I for batch mixers and 100 I for continuous mixers (see 5.3.4). Afterwards, the specimens for particular variance tests are prepared. ISO 18650-2 pdf free download.
