Investigation of basaltic aggregate material properties under different mechanical and environmental conditions

In this study, the variation in aggregate properties, which are produced from two different basaltic rocks (i.e. fine and coarse grained basaltic rocks), are investigated under different mechanical and environmental conditions. Firstly, effecting factors on rock and aggregate durability are mainly summarized and remarkable studies based on ballast aggregates (31.5 ‒ 63.0 mm) and ballast stratum are expressed. Desired technical properties of ballast aggregates used in our country are given and important problems observed in ballast stratum are referred. During field studies, geotechnical properties of rock masses, from which the aggregates are produced, are determined and they are classified in terms of distinguishing different weathering grades. General physical, mechanical and aggregate properties of the rocks are determined by using the samples obtained from rock masses with different weathering grades. As a result of aggregate tests carried out on different size fractions (i.e. 10 ‒ 14 mm and 31.5 ‒ 50.0 mm) of aggregates, potential usage areas of aggregates produced from unweathered (W0) and slightly weathered (W1) rock masses are determined in terms of present approaches. An experimental procedure are developed to determine the strength of ballast aggregates in the train route and then the variations in rock material and ballast aggregate (31.5 ‒ 50 mm) properties are investigated under different environmental and mechanical conditions. Environmental conditions are represented by magnesium sulfate soundness tests with different cycles and mechanical conditions were represented by single particle breakage and Los Angeles abrasion loss tests with different number of revolutions, respectively. As a result of laboratory studies, the variation in shape properties of ballast aggregates has enormous effects on ballast strength and fragmentation degree. The long-term durability of ballast aggregates are investigated in terms of Los Angeles abrasion loss tests with different cycles and number of revolutions. According to the results obtained from these studies, it can be claimed that the fragmentation degree of ballast aggregates is associated with mineralogical variation and grain size. Furthermore in order to predict Los Angeles abrasion loss and the degree of fouling of ballast aggregates, several empirical formulae are developed. Suggestions are given in order to investigate the actual fragmentation mechanism of ballast aggregate in-situ.