Railroad Ballast Prescription: State-of-the-Art

Abstract

A review of ballast prescriptions for specification writing is combined with new research data to outline typical requirements for selecting ballast. A method of classifying ballast for predicting performance is also given which should help in economic evaluation of different ballast sources. Ballasts used by railroads can be divided into three main grading divisions based on maximum particle size and dependent on maintenance procedures. These three sizes are nominally 65 mm., 40 mm., and 25 mm (2.5-in., 1.5-in., and 1.0-in.). Gradings used in Europe and Japan are generally uniform although evidence presented indicates broadly graded ballast should perform better. This resulted in recommended sizing and gradings. Particle shape requirements and tolerances are summarized. On minor lines, where a good rock source is not locally available, gravel ballast should be considered as an economic alternative to transported crushed rock.