Morphology Comparison of Different Mineral Coarse Aggregates Produced from Two Typical Crushers

Morphological characteristics of coarse aggregates, namely shape, angularity and surface texture, are closely related to rock mineral compositions and crushing mechanisms. Aggregates with different mineral compositions should be crushed using a suitable crusher. To explore the influence of mineral and crusher types on aggregate morphology, this study investigated the effect of the mineral compositions and crushing operations on the morphologies of coarse aggregates. Six types of major rock-forming minerals (i.e., quartz, amphibole, potassium feldspar, sodium feldspar, calcite and pyroxene) were selected and two typical crushers (i.e., jaw crusher and impact crusher) were used. The morphology parameters (i.e., angularity, texture, sphericity and F&E) of coarse aggregates were measured using the Aggregate Image Measurement SystemII (AIMSII). Further, the morphologies of different aggregates produced by two crushers were compared. The results showed that the angularity values of some aggregates crushed by a jaw crusher (average 3451) were bigger than those by an impact crusher (average 3067) and the angularity of the harder mineral was less affected by the crusher. For surface texture, there was no significant difference between these two crushers, with average texture index of 333.83 for the impact crusher and 332.67 for the jaw crusher, indicating that the surface texture of aggregates was mainly affected by their compositions and barely influenced by the crushing operations. The shape results indicated that the impact crusher produced more cubical aggregate particles compared to the jaw crusher, with average sphericity of 0.666 versus 0.607, whereas the jaw crusher produced aggregates with more elongated or flat particles, with an average F and E index of 3.331 versus 2.726. This study fills the research gap that few previous investigations focused on-the crushing morphology of single mineral aggregates-and the findings help us to understand the effect of the mineral compositions and crushing operations on the morphologies of coarse aggregates, which in turn guides the selection of suitable crushers for different minerals.