Closure to "Effect of rubber crumbs on the cyclic behavior of steel furnace slag and coal wash mixtures" by Yujie Qi, Buddhima Indraratna, Ana Heitor, and Jayan S. Vinod

The practical application of waste materials such as steel furnace slag (SFS) and coal wash (CW) is becoming more prevalent in many geotechnical projects. While adding rubber crumbs (RCs) from recycled tires into mixtures of SFS and CW not only solves the problem of large stockpiles of waste tires, it also can provide an energy-absorbing medium that will reduce vibration and prevent track degradation. Thus, the engineering insight into the effect that rubber crumbs have on the dynamic behavior of SFS + CW + RC mixtures is in urgent demand. In this study the influence that RC contents and confining pressures have on the deformation, resilient modulus, damping ratio, and shear modulus was investigated by cyclic triaxial tests. Test results reveal that with the inclusion of RC, the axial strain, volumetric strain, damping ratio, and energy-absorbing capacity of the SFS + CW + RC mixture increase, while its resilient modulus and shear modulus decrease. Based on these properties, an amount of 10% RC is recommended as an optimal blended mix to be used as railway subballast. A three-dimensional (3D) empirical model of the relationship between the maximum axial strain, volumetric strain, and resilient modulus with RC contents and the effective confining pressure was developed, and the energy-absorbing capacity of these waste mixtures has also been analyzed for practical purposes based on their comprehensive parameters