Assessment of the Use of Polypropylene Fiber Reinforced Foam Concrete as a Subgrade Material for the China Railway Track System (CRTS) III Slab Ballastless Tracks

Abstract

This paper presents the application and the development of foam concrete (FC) to replace the traditionally used subgraded materials (typically compacted soil or granular earth rock) in high-speed railway by using cement to sand ratio of 2:1 with a target density of 500 to 700 kg/m3 and by adding polypropylene (PP) fibers with 0.25% and 0.40% by volume to improve the properties of FC. The mechanical properties were evaluated and tested in the laboratory in accordance with ASTM standard method, including compressive strength, tensile strength, modulus of elasticity and Poisson’s ratio, and dynamic strength. In addition, the numerical model investigates the performance and analyzes the effect of applying the full cross-section PP fiber reinforced FC in slab ballastless track, under different thicknesses, on the dynamic response of the whole structure, and then compares them with that of the traditional structure. The results indicate that the strength of FC with a density of 500 to 700 kg/m3 can meet the requirements of static and dynamic loading conditions of railway earth structure. But the density of 600 to 700 kg/m3 shows good strength stability under different curing states. In addition, adding 0.25% PP fiber is an optimal volume that can significantly improve mechanical properties. The prediction of the model shows that FC at a density of 600 kg/m3 by adding PP fibers of 0.25% at a thickness of 1.5 m can reduce the stress and vibration of the track structure better than that of the traditional structure; this indicates a long-term maintainance stability of the subgrade bed.