The influence of rock raw materials comminution in various crushers and crushing stages on the quality of mineral aggregates

This article concerns the optimal utilization of various impact and jaw crushers at a variety of crushing stages of technological circuits in order to obtain suitable aggregates quality. The first part of the paper characterizes the basis of crushing forces occurring in the crusher and their relationship with comminution effects. The aim of the paper was to outline the research methodology for different variants of technological circuits (Fig. 1) and comminution effects (Figs 5-9, Tables 1 and 2). This work also describes the accepted three-stage investigation programme. The first stage of the investigations concerns plant scale aggregates production in the Austrian gravel-pit Viecht namely, collecting samples of slat impact crusher products, sample analysis, and preparation for further investigations. The second stage includes crushing and analyses of product froma jaw crusher and the unique impact crusher (in the laboratory of SBM Mineral Processing in Laakirchen), while the third part concerns crushing in a jaw crusher and grinding operations in a Bond’s mill (AGH University of Sciecne and Technology laboratories). This three-stage investigation programme enabled the realization of three and four-stage crushing circuits’ performance analysis (Chapter 2, Fig. 1). For an assessment of the crushing effects in consecutive comminution stages, it was necessary to determine the following: the indices of irregular particles content (the flatness index), the content of fine particles below 1 mm, the reduction ratio index, and the energy consumption; and for the assessment of crushing effects in the last comminution stage, the content of particles below 1 mm obtained in the Bond’s mill at one hundred revolutions (Chapter 3, Figs 5-9, Table 1 and 2). The summary section draws attention to the advantages and disadvantages of utilizing various crushing devices at different crushing stages. It was stated that for the production of coarse gravel aggregates used in the construction and road building industries multi-stage crushing circuits with impact crushers would be the most advantageous because they produce cubic particles with increased comminution resistance, while jaw crushers in such a circuit could be utilized in the preparation of semi-products for the grinding processes of fine aggregates (flours) production.