Atterberg limits of baseball infield soils containing over-size particles, Part I: effect of particle size

Context. The performance of baseball infield playing surfaces greatly depends on soil water content. Therefore, Atterberg limit tests may be useful when evaluating baseball infield soils because these tests directly link soil behaviour to water content. The tests’ utility for this application is limited by the standard practice of removing particles larger than 425 μm. Removing particles of 425–2000 μm makes it difficult to compare results for soils having different sand gradations because different amounts of sand are often removed. The implications of leaving particles of 425–2000 μm in the sample are not known. Aims. This research was conducted to re-appraise the practice of removing ‘oversize’ particles prior to Atterberg limit testing and to clarify the oversize particles’ influence on the test results. Methods. Six size grades of granular particles (termed ‘coarse additions’) corresponding to five individual size ranges of sand (2000–1000, 1000–500, 500–250, 250–150, and 150–53 μm) and silt (i.e. finer than 53 μm) were mixed with a kaolinitic clay at 0–80% coarse addition. The liquid limit (LL) and plastic limit (PL) were determined for each mixture. Key results. The LL and PL decreased proportionally with sand or silt additions up to about 30% coarse content. Above 30%, particles finer than 425 μm produced greater deviations from the expected LL and PL than did the particles coarser than 425 μm, which would be prevented using current standard test methods. Conclusions. Mixes containing these ‘oversize’ particles did not preclude the ability to complete the Casagrande cup or thread rolling tests, and in fact gave more predictable results than the currently-allowed particles, particularly those less than 250 μm in diameter. Implications. This research suggests particles of 425–2000 μm can remain in soils during Atterberg limit tests. These findings may improve the utility of LL and PL tests for comparing baseball infield mixes.