Predicting the Brittleness of Rocks From a Crushability Index

The determination of brittleness, an important mechanical property of rocks, requires some standard tests which are time consuming and expensive. The sample preparation and testing methods are easy in the crushability test suggested in this study and a small amount of crushed rock is enough for testing. That the crushability test can be applied on the drill cuttings is another important advantage. The prediction of brittleness from the crushability test will be useful for some cases. 500 g oven-dried crushed samples, in the size range of 19.0−9.52 mm, were prepared from twenty four different rock types. After charging the samples to a jaw crusher, the crushed materials were passed through the 9.52 mm mesh and the percentage of oversized material was described as the crushability index (CI). The brittleness B1 determined from the Protodyakonov impact test and the brittleness B2 determined from compressive and tensile strength were evaluated in this study. A significant strong correlation was found between the CI and the brittleness B2. Because the tested rocks cover sedimentary, igneous, and metamorphic rocks, the derived relation can be generalized. It can be concluded that the crushability test is a practical and easy method for the prediction of brittleness B2.