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Bond standard test alternative procedures
Alternative procedure to the Bond standard test is based on determining the grindability of an unknown ore by comparing it to the grindability behaviour of a reference ore. It can be performed in any laboratory ball mill, but it requires a reference sample ore for which wi is known.
Determining the Bond index using the Fred Bond method  is considered the state-of-the-art methodology for mill calculations and a critical process parameter in raw materials selection and grinding process control. Although it is usually referred to as a standard test, no ISO (International Organization for Standardization) or ASTM (American Society for Testing and Materials) standard procedure has been established, so the primary reference used worldwide to define the procedure is the original proposal from Bond. Despite this, the knowledge of the Bond standard test is enriched continuously with new research, as is the case of the recently published work by García et al. , which presents a deep analysis of the test procedure and evidences the importance of the grindability index (proposing it to be renamed as the Maxson index), or the recent proposal by Nikolić and Trumić , which represent a new approach for determination Bond work index on finer samples.
Alternative tests soon arose after Bond’s proposal to avoid the need for the standard mill and time-consuming procedure. Therefore, papers dealing with this problem are numerous, aiming to discuss the validity of simpler and quicker methods to determine the Bond work index ( w i ). Some of them use the standard mill, while others use a non-standard mill or are based on computation techniques. It is worthy to mention the development of other approaches to grindability evaluation based on impact breakage tests. The drop weight test has proven its validity and scaling-up possibilities under certain conditions .
There are not many review papers describing alternative methods of ball mill w i determination. The work of Lvov and Chitalov  is probably the most recent one, and it performs a sound analysis of several alternative methodologies.
2. Alternative Procedures to the Bond Ball Mill Standard Test
Alternative abbreviated and simplified procedures for determining the work index have been proposed through the years.
- Alternative tests that simulate the standard Bond test with an abbreviated procedure;
- Alternative tests based on determining problem sample grindability using a reference sample with wi known.
Alternative tests from the first group are based on the use of a Bond standard ball mill for the reach the steady-state more quickly [28,29,30] or for performing the mathematical simulation of the standard test [13,14,21,22,27].
Alternative tests from the second group can be performed in a different mill, usually needing less sample than the standard procedure. All of the methods aim to give a close estimation of the Bond work index when the standard Bond ball mill is not available and are faster procedures with a reduced number of grinding steps. The longest alternative test requires 3–4 grinding cycles, while the shortest one can be performed with one grinding cycle. It must be considered that the standard procedure compels a minimum of 5 grinding cycles, with 7–10 grinding cycles usually being necessary.
In general, the mean square error data presented cannot be understood as a validity indicator, for in some cases, the reported value was based on just a few tests or with few ores. However, these data indicate that shorter procedures (i.e., with just one grinding cycle) are usually less reliable, yielding a higher mean square error. Nevertheless, due to the advantage in laboratory time, they could be recommended if ore feed is the same, which could be the case of the periodic grindability control in a specific mine.
Finally, after an adequate grinding kinetic behaviour characterisation of the ore, alternative tests based on the simulation of the standard Bond test could be recommended when considering the process digitalisation as part of the global digitalisation strategy in the mining industry.
The entry is from 10.3390/met11071114
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- GMG-Global Mining Guidelines Group. Determining the Bond Efficiency of Industrial Grinding Circuits. 2016. Available online: (accessed on 30 May 2021).
- García, G.G.; Oliva, J.; Guasch, E.; Anticoi, H.; Coello-Velázquez, A.L.; Menéndez-Aguado, J.M. Variability Study of Bond Work Index and Grindability Index on Various Critical Metal Ores. Metals 2021, 11, 970.
- Nikolić, V.; Trumić, M. A new approach to the calculation of bond work index for finer samples. Miner. Eng. 2021, 165, 106858.
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- Gharehgheshlagh, H.H. Kinetic grinding test approach to estimate the ball mill work index. Physicochem. Probl. Miner. Process. 2015, 52, 342–352.