Attrition Kinetics of the Los-Angeles-Test

The Los Angeles test is a widely used standard method for quality control of railway ballast. It is commonly believed that there is an inversely proportional relationship between the test result LA_RB and the resistance to fragmentation. This implies that the fines are generated by fragmentation only. In this study, an extensive test series with four rock types and an in-depth analysis of particle geometry and petrography are carried out using advanced imaging techniques. The amount of fragmentation, rounding and abrasion contributing to the test result is estimated. The test shows approximately 3–5% (Mass-%) of fines not caused by fragmentation, but by rounding and abrasion, regardless of the magnitude of the LA-value itself. An analysis of particle size distributions after the test shows that the fines proportion can in some cases be a misleading metric.