The article shows investigations on the behavior of preplaced aggregate concrete with regular and irregular coarse aggregates. The thermal properties, compressive strength, and internal structure were analyzed based on computed tomography images. The regular and irregular shapes of aggregates were obtained according to patented technology, which is possible to produce in both laboratory and industrial conditions. Based on the conducted calculations, heat storage capacity was assessed. The influence of grain shape on the material strength, porosity, and hydration gaps was determined. Debonded porosity, as a result of aggregate impurities, was shown using computer tomography analysis. It was shown that the arrangement and shape of the grains has a significant impact on the performance properties of hardened preplaced concrete.

No abstract

Abstract. Article describes issues related to the assessment of raw materials grinding efficiency in an electromagnetic mill. Application of such type of mill in grinding processes can result in measurable benefits of more efficient raw material grinding by reducing time needed to produce a product of a suitable particle size compared to conventional mills. The expected effect of application of a system based on an electromagnetic mill is to achieve a lower energy consumption of grinding process for raw material processing compared to the existing equipment used for the fine grinding. A key element of correct design of comminution circuits in processing of particular feed mineral is to identify the impact of key factors affecting the efficiency of the grinding process. The most important factors determining the efficiency of the grinding process are the time, the construction parameters of the machine, the type of grinding media used in grinding process, as well as the parameters of the feed, among others the crushing resistance or particle size. The paper presents the results of kinetic study of copper ore grinding in electromagnetic mill for variable feed particle size distribution of and different sizes of grinding media.

The article concerns the issues of flotation process effectiveness in relationship to the operating conditions of a high-pressure comminution process course. Experimental programme covering a flotation laboratory batch tests was a verification technique of a high-pressure crushing operations course. The most favorable values of flotation concentrate weight recoveries were obtained for the pressing force 6 kN and 4% of the feed moisture. It was also determined the model of the concentrate weight recovery as a function of pressing force in the press and feed moisture content. This model was the basis for the optimization of effects of copper ore flotation processes preceded in high-pressure crushing operation in roller presses.Keywords: high-pressure grinding rolls, flotation, copper ore W przedstawionym artykule przebadano efektywność procesu flotacji w zależności od warunków pracy technologii wysokociśnieniowego rozdrabniania w prasach walcowych. Zrealizowane testy flotacyjne stanowiły technikę weryfikacji przebiegu procesu rozdrabniania nadawy. Najwyższe wartości wychodów koncentratów flotacyjnych uzyskano przy sile nacisku w prasie wynoszącej 6 kN oraz wilgotności nadawy 4%. Wyznaczono model wychodu koncentratu flotacyjnego jako funkcję siły nacisku w prasie oraz wilgotności nadawy. Model ten był podstawą optymalizacji efektów procesu flotacyjnego poprzedzonego rozdrabnianiem rudy w wysokociśnieniowych prasach walcowych.

The article regards the issues related to chalcedonite processing by means of particle size classification as well as densimetric separation. Chalcedonite is an unique rock and material with wide industrial applications in various industries. The investigative program included laboratory tests of chalcedonite classification in the classifier and the jig, as well as separation of the material in the dense liquid. The obtained results indicate that the products of particle size classification of chalcedonite in the classifier are characterized by a different chemical and mineralogical composition. The 0-0.3 mm particle size fraction contains over 96% of quartz, while the fine size fraction below 0.063 mm contain about 80% of quartz and 20% of clayish minerals. In the next stage of the investigative program, the densimetric separation of chalcedonite material in the jig and in dense liquid, was carried out. The results of the density classification in the jig indicate the different absorbability of the obtained chalcedonite density fractions. Fractions with a higher density were characterized by lower water absorption. The results of separation in the dense media liquid also showed that the obtained aggregate products are of significant differences in absorbability as well as high variability of the strength parameters. The results of the investigations show that the obtained products of the classification can be more efficiently utilized in industry, due to their diverse chemical and physical characteristics.