Investigating the potential valorization of phosphate mine waste rock as railway ballast alternative aggregates: a novel opportunity to advance sustainable transport infrastructure initiatives

Railway ballast is always in demand since it provides the fundamental support for rail tracks all over the world. Railway ballast is essential for maintaining the stability and durability of train infrastructure. The requirement for this material is driven by the increasing need for efficient transportation networks induced by the growing population and rapid urbanization. More evidence of the need for a sufficient supply of ballast comes from the development of high-speed rail initiatives and the upgrading of current rail networks. To meet this demand, environmentally-conscious sourcing methods and creative approaches to addressing environmental issues are needed, meanwhile maintaining the dependability and effectiveness of railway networks worldwide. Millions of tons of mining waste consisting of various components are produced annually by phosphate extraction activities, including those at the Benguerir mine in Morocco. Ballast materials are often composed of higher quality igneous or metamorphic rock; this work is unique for its novel approach to study the possibility of manufacturing railway ballast aggregates from sedimentary-origin mining waste. The three hardest lithologies -flintstone, phos-flint, and dolomitic limestone- are the subject of this study. A comprehensive assessment was conducted, including: (i) petrographic characterization, (ii) environmental and health behavior analysis, (iii) geometric requirement verification, (iv) physical characterization, (v) chemical and mineralogical evaluation, (vi) geotechnical analysis, and (vii) durability tests. The results indicate that these sedimentary-origin materials do not meet the mechanical performance standards required for railway ballast. However, their potential for use in other applications, such as concrete aggregates and road construction, is promising.