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In this work, the microstructure of titania coating fabricated on the surface of hydrostatically extruded titanium grade 4 with the use of the micro-arc oxidation method was studied. The surface topography and microstructure investigations performed with atomic force microscopy and scanning and transmission electron microscopy revealed that, by using an Na2HPO4 electrolyte, a well-adherent porous coating is produced on the top surface and side walls of the extruded rod. The distribution of chemical elements was analyzed by using energy dispersive X-ray spectroscopy. The chemical elements dissolved in the electrolyte i.e. (Na, P and O) incorporated into the coating. Sodium locates preferentially in the outer part of the coating, while phosphorus and oxygen are distributed throughout the whole coating. The most relevant finding shows that a grain refinement caused by a hydrostatic extrusion provoked an increase in density of high-angle grain boundaries (HAGB), which in turn secured the formation of a continuous amorphous layer close to the substrate. The presence of this layer compensates for the effect of anisotropic substrate, producing a comparable and homogenous microstructure with a large number of micropores.

A new hypothesis concerning a process of the mining solid rocks using bucket wheel excavators (BWE). Destroying of the rock mass structure is a result of breaking and not, as so far accepted, of cutting. This approach excludes, for the description of solid rock workability using bucket wheel excavators, used classifications based on individual linear or surface resistances of cutting. The possibility of a replacement mechanism for determining of the workability by bucket wheel excavators using rippers was assumed. On this basis, an innovative method for assessing the workability of solid rocks was developed, which is a combination of an derived empirical energy relationship LSE of breaking by tractor rippers from a compressive strength, a seismic wave velocity, a density of solid rock, and the modified classification of workability by bucket wheel excavators according to Bulukbasi (1991). The proposed method allows for multi-parameter assessment of the workability class based on the parameters that are independent variables in the specified dependencies.

The examination of the amount of the natural aggregates production in the European Union countries in the last decade was the aim of this research. In the modern history of development of natural aggregates production in European countries we can distinguish two major period. First period includes time before the economical crisis (up to year 2005). The second period correspond to economical crisis after year 2008. The annual production of aggregate in Europe is around 3 billionMg valued ca. 20 billion euro. The majority of aggregates (around 91 %) is derived from natural deposits. Crushed aggregates constitute around 50% and sand&gravel aggregates about 41%. The remaining amount is made up artificial aggregates (around 2%), recycled aggregates (around 5%) and marine aggregates around 2%). The aggregates industry in Europe includes around 17 000 companies which extract around 29 000 open pit mines. This extraction chain gives around 280 000 workplaces. The conducted analysis has shown that the quantity of produced aggregates in individual countries presents changeable tendency. It has been increasing and decreasing in the EU and UEPG countries, but in most of them the tendency of produced aggregates has stayed on the stable level. However the picture had been disturbed by the world economic crisis. After 2008 the production of aggregates in the majority of European countries decreased and this tendency lasts still, though with various intensity. Nevertheless, Poland distinguished itself with systematically growing production of aggregates (till 2011). The average per capita production in Europe in 2011 was around 5.8 Mg/per capita. Comparing to year 2006 (ca. 7.0 Mg/per capita) the production decreased by about 17%. In Poland in years 2006-2011 the aggregates per capita production increased from 4.4 Mg up to around 9.1Mg. i.e. by about 107%. Year 2011 had the main influence on this trend - aggregates production amounted to around 345 million Mg (increase by about 36.9% comparing to year 2010).

Natural aggregates are the basic group of extracted minerals. In Poland, their share in the extraction of solid minerals over 30 years (1989–2018) increased from about 24% to 54%. Current aggregate production is about 300 million Mg and in 2019 it will probably exceed the record volume of 2011 – over 330 million Mg. In the extraction and production of aggregates in Poland, there is a decisive preponderance of gravel and sand aggregates – their share in the total production of natural aggregates amounts to 70–75%. The remaining part consists of crushed-stone aggregates produced from compact and moderately compact rocks of magma origin (basalts, granites, gabbro and diabases, melaphyres, porphyry, syenites, etc.), sedimentary rocks (dolomites, limestones, sandstones, etc.), and metamorphic rocks (amphibolites, migamatites, gneisses, serpentinites, etc.). A gradual deterioration in the quality of the raw material base of gravel and sands as well as a simultaneous increase in the demand of the construction industry for the best quality thick aggregate fractions (5/8mm, 8/11, etc.) has a significant impact on the rise in the amount of hard to sell and unsalable (waste) fractions of aggregates produced in Poland. This applies especially to gravel and sand aggregates in whose deposit the share of fine fractions (below 2 mm) is systematically increasing, while the demand for them in the construction sector is limited and they are often treated as useless (waste) material. Since it is practically unknown what is the production and consumption of these aggregates, an attempt was made to assess the amount of extracted and produced sand and gravel fractions of natural aggregates in Poland. The deficit of natural aggregates in many countries and regions as well as the limited aggregate resources in Poland and increasing difficulties in obtaining licenses for their extraction indicate the need for selective storage of sand aggregate assortments instead of “melting” them in post-mining excavation pits. The presented research results should contribute to the development of more accurate market forecasts regarding the demand for and production of natural aggregates in Poland and in individual regions, especially when it comes to gravel and sand aggregates, including also fine fractions.

The problem concerning the growing demand for natural aggregates and the need to limit costs, including transportation from remote deposits, cause the increase in growth of interest in aggregates from mineral wastes as well as in technologies of their production and recovery. The paper presents the issue related to the group of aggregates other than natural. A common name is proposed for such material: “alternative aggregates”. The name seems to be fully justified due to adequacy of this term because of this raw materials origin and role, in comparison to the meaning of natural aggregates based on gravel and sand as well as crushed stones. The paper presents characteristics of the market and basic application of aggregates produced from mineral wastes, generated in the mining, power and metallurgical industries as well as material from demolished objects.