Railway ballast behaviour of steel furnace slag aggregate under monotonic triaxial load

Abstract

Nowadays, there is a strong pressure to use industrial byproducts and recycled materials in civil engineering works. In Portugal, for example, several studies have been carried out with the aim of demonstrating that some industrial byproducts exhibit good mechanical properties and can be used instead of natural materials, providing technical and economic advantages without environmental and public health risks (Fortunato and Pardo de Santayana, 2007). One of these materials is the “Inert Steel Aggregates for Construction (ISAC)” (Gomes Correia et al., 2012). One of the potential applications of ISAC is the railway ballast layer. However, there is a lack of geomechanical studies to demonstrate their suitability for this function. In this way, a study to evaluate the applicability of ISAC as ballast material for rail tracks (conventional and heavy haul with 40 ton/axle) is underway at the Faculty of Engineering of the University of Porto (FEUP) Geotechnical Laboratory (LabGeo). Triaxial tests with reduced scale ballast samples in a ratio of 1:2.5 are being carried out to compare ISAC with natural aggregates usually used in the ballast layer (granite aggregate). The laboratory test program comprises traditional monotonic triaxial tests to evaluate the shear strength of the material and triaxial cyclic loading tests to evaluate the resilient behaviour and the permanent deformation. This paper presents the results of the monotonic triaxial tests, which aim to evaluate the maximum limit of cyclic loads to be applied in repeated load triaxial tests. This issue is particularly relevant considering that in those future studies, the aim is to simulate cyclic loads which represent the heavy haul trains.