The investigation of additive manufacturing and moldable materials to produce railway ballast grain analogs

Abstract

The size and shape of individual grains play an important role in the mechanical behavior of granular materials such as the strength and the stability of railway ballast. The aim of this research is to investigate materials from which reproducible grains with irregular convex geometry can be produced by molding and additive manufacturing technologies in order to create replicable artificial railway ballast assemblies that can be used in experiments. Packings with controlled grain shape results more controlled investigations contrarily to using natural grains with random geometry. Specimens were made from railway ballast materials, three groups of moldable materials (materials used in the construction industry, thermosetting polymers, and certain low-strength materials) and additively manufactured polymers. Uniaxial compression and bending tests were performed on these specimens. The mechanical properties of typical railway ballast materials (basalt and andesite) were compared with the properties of artificially produced materials. Of the moldable materials, we recommend the use of polyester resin, mixed with fine-graded crushed stone aggregate or the application of ceramic powder. Furthermore, the PolyJet and Multi Jet Fusion additive manufacturing technologies produced specimens with the closest mechanical properties to basalt and andesite.