Ballast Type Ⅳ and the control ballast exhibited the highest overall degradation rates, but all test boxes showed increased fines accumulation in the lowest sections as compared to the upper sections. The upper ballast section of Type I ballast was the only ballast at the test conclusion that was still within the AREMA 4a new ballast gradation limits, but more fines were evident in the lowest section. Infiltration of mineral particle contamination from passing boxes upward except in the control section, where significant fine material was present at the beginning of the test. Because this test was performed on a high mgt revenue service line undergoing periodic alignment and maintenance, test results may have been influenced by these activities.
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