Polyurethane-based stabilization of railroad ballast – a critical review

In the recent past, the use of polyurethane polymers to stabilize the ballast is on rise. This paper presents a critical review of different polyurethane stabilization techniques used across the world to treat railroad ballast. The main aim is to explore the effect of polyurethane polymers on the bonding between the ballast particles and its subsequent role in improving the ballast strength and reducing the track settlements. A review of literature reveals that the polyurethane coating enhances the shear strength and reduces the ballast degradation under direct shear conditions. The polyurethane treated ballast has also shown lesser vertical settlement and plastic strain compared to untreated ballast under cyclic loading. These findings are supported by the results from numerical simulations as well. The field studies on polyurethane treated ballast have also confirmed the role of polymer in strengthening the ballast that eventually reduces the track maintenance costs.