Effect of Tire Chips on the Shear Behavior of Steel Slag and Granite Ballast Mixture

With a view to reduce burden on natural resources, the use of steel slag ballast (SSB) as an alternative to the conventional granite ballast (GB) is explored in the current study. The shear behavior of GB, SSB, and slag-GB mixture with and without tire chips (TC) was evaluated under direct shear conditions. The test results indicated that SSB exhibits significantly higher friction and dilation angles ( φ and ψ) and lower particle breakage ( Bg) when compared with GB. Furthermore, it was observed that, with the addition of TC, the magnitude of φ, ψ, and Bg of both granite and steel slag samples reduced considerably. Moreover, the friction and dilation angles of slag-GB mixture were found to be directly dependent on the proportion of slag in the mixture. For instance, the values of φ, ψ, and Bg in the case of SSB20 (20% SSB and 80% GB) were 59.36°, 13.35°, and 8.26% when compared with 58.31°, 12.98°, and 8.51% in the case of GB, and 61.66°, 15.35°, and 6.81% of SSB. However, SSB80 was found to exhibit an almost similar value of φ (i.e., 61.51°) as that of SSB but with a lower value of ψ (14.89°). In this context, the optimum content of slag in the slag-GB mixture may be considered as 80%. Furthermore, the optimal range of TC to be added was determined to be 4% to 8.6% for SSB80 to attain a friction angle similar to that of GB.