RESUMO
The use of mineral aggregates is related to the increasing demand in construction, railway and road infrastructures. However, mineral aggregates can appear to be of variable quality, directly affecting their suitability for respective earthwork applications. Since the production of mineral aggregates should ensure the standardized, high-quality requirements of the final product, rock-crushing mechanisms should be investigated in a detailed manner. In this context, the aim of the present study is to evaluate and analyze the geometric parameters of basalt aggregates as a result of several rock comminution processes. Basalt aggregates from two deposits in Poland were used in the study. The samples are differentiated regarding both lithological variances, mineral composition as well as the host rock's tuff content. The rock comminution processes were conducted using two types of crushers, namely the laboratory-scale jaw and cone crushers. The feed for crushing was designed based on the original geometric grain composition and the separated feed in the form of flaky and non-flaky particles. The crushability test results demonstrated that the interparticle compression in the jaw crusher resulted in finer products compared to the one in the cone crusher. It was also observed that the flakiness and shape indexes decreased after crushing, both in the feed with the original geometric composition of the grains and those with flaky and non-flaky particles. Nevertheless, a higher flakiness index was obtained after the crushing of non-flaky particles and a lower one after the crushing of flaky particles. The flakiness index for grains below 16 mm after the crushing process was less than 10%, which indicates a more favorable result compared to the original feed. In addition, it was shown that flaky and non-cubical particles were accumulated in the finest (below 8 mm) and coarsest (above 20 mm) fractions in jaw and cone crushing processes, receiving flakiness and shape indexes ranging up to 80-100%. Finally, it was also observed that the lithological variances of the feed material have a significant impact on the particle size distribution of the product. More profoundly, basalt aggregates with a higher tuff content and weathering degree have a higher degree of crushing. The present study, in this context, provides accurate and satisfying information on understanding the crushing mechanisms of two important crushing equipment as well as their rock-crusher interactions.
RESUMO
The aim of this publication is to analyze the influence of rock mineral composition and rock geometric properties on the quality of crushed aggregates, from the perspective of selecting an adequate aggregate production technology. This research is based on samples of crushed aggregates from plants processing igneous rocks from four different igneous deposits. In the case of the geometric properties, shape and flakiness indexes were identified and subsequently analyzed along with particle size distribution. The performed tests allowed a conclusion that the shape of the particle is influenced by the mineral composition and size distribution. The grain size analysis demonstrated that flaky and non-cubical particles concentrate in the finest grain fractions, and the least variable shape index is observed for basalt aggregate. Some problems were also observed to exist in relation to the classification of grain shape. In the literature, the notions of regular and irregular grains seem to be used interchangeably with the notions of flaky and non-flaky grains. The performed tests show that flaky grains do not necessarily have to be non-cubical and vice versa. Therefore, this article proposes an approach in which the applied technique is precisely explained and the shape of grains is described with four notions: cubical, non-cubical, flaky, and non-flaky. The article also finally concludes that the next step in the research on selecting an optimal production technology of high-quality aggregates should be to analyze the selection of the fragmentation process while also characterizing the geometric properties of the aggregates.
