Repeated Load Aggregate Degradation

Abstract

Degradation of a variety of aggregate types, commonly used as ballast by the CN and CP railroads in Canada, and a non-ballast, were evaluated in the laboratory under different gradings, applied stresses, and density conditions. The ballasts were subjected to the one-dimensional and triaxial repeated loading stress states, encompassing some of the conditions likely to occur under tie-ballast track support systems. The results of these tests have demonstrated that the Mill Abrasion (MA), which is a measure of an aggregate's hardness, and the Los Angeles Abrasion (LAA), which measures the toughness of the aggregate, are the best indicators of degradation performance of an aggregate subjected to repetitive loads. The results also suggest that these material characteristics can be used to evaluate unbound aggregates for use in highway and airfield pavement structures as similar aggregate types are utilized in these systems as well. For the covering abstract see ITRD E118503.