Laboratory investigation of the cyclic behavior of rock ballast mixed with slag ballast for use in railway tracks

Abstract

In this paper, the combined behavior of igneous (andesite) rock ballast and EAF slag ballast has been investigated. In the first step, to accurately identify the phases that make up the materials, the properties of both materials have been evaluated and compared using X-ray fluorescence (XRF) and X-ray diffraction (XRD) tests and also physical tests. Then, five samples containing combinations of rock and slag ballast, including 0 %, 25 %, 50 %, 75 %, and 100 % slag, were prepared. Finally, the abrasion resistance of samples was investigated by performing the Los Angeles and micro-Deval abrasion tests, and by conducting ballast box tests, settlement, breakage, stiffness, and damping ratio of each sample were determined under cyclic load. According to the Los Angeles abrasion test results, by increasing the percentage of using slag ballast in the samples, the abrasion increased from 19.38 % to 23.91 %. While in the same samples, the micro-Deval abrasion decreased from 13.4 to 9.3. According to obtained results of the ballast box test, the settlement of slag ballast was 33 % less than rock ballast, but the ballast breakage index of slag ballast was 146 % more than rock ballast. The stiffness and damping ratio of samples were calculated according to the hysteresis loop. The results illustrated that the use of slag ballast increased the stiffness of the track by 35 % compared to rock ballast. Furthermore, increasing the percentage of slag in the sample brought about a rise in the damping ratio as the damping ratio of the 100 %SB increased by 76 % compared to the 0 %SB. Eventually, by examining the obtained results and comparing the stiffness and damping of the samples with the 0 %SB, in the 75 %SB, the increase in damping compared to the 0 %SB was very significant; however, the increase in stiffness did not change significantly. Thus, the 75 %SB as a suitable combination of slag and rock ballast was suggested.