Abrasion testing and armourstone degradation

Abstract A cylindrical tumbling mill apparatus is used to provide weight loss and shape change data on rock fragment abrasion from four experiments Weight loss data for the four limestone samples confirm the reproducibility of the test conditions and of the abrasion resistance index value which had been reported previously for this rock type Progressive shape changes of subsamples are analysed using recently developed automated image analysis techniques and computer methods based on Fourier and Fractal shape descriptors. A theoretical relationship between weight loss, revolutions in the mill and surface roughness is developed. A single shape descriptor is chosen to account for the role played by shape and roughness in changing the rate of weight loss. The experimental data is consistent with the theory when the single descriptor is the Fourier Asperity Roughness Factor as defined in this paper. Weight loss-time, and asperity roughness-time relationships are determined and their application to armourstone rounding is discussed. Examples from a hard and a soft limestone are given to illustrate the use of the tumbling mill aggregate abrasion test in the prediction of wear of armourstone after a certain number of years in service.