Assessment of the quality of crushed stone screenings

Abstract

Purpose. Assessment of the quality of crushed stone screenings accumulated in the mine waste dumps of three quarrying enterprises to determine their resource potential and provide scientific justification for the most rational directions for processing. The methods. The assessment is carried out by sampling averaged samples using the coning and quartering method from different horizons of the waste dump to ensure representativeness. Laboratory studies included the determination of key physico-mechanical and chemo-mineralogical indicators. Specifically, sieve analysis was used to establish the particle size distribution (granulometry), and the chemical composition was determined using high-precision X-ray fluorescence analysis (XRF). Particular attention was paid to the content of critical fractions and main oxides. Findings. According to the research results, the following sample values were established: the content of the fine fraction (0–0.63 mm) in the studied samples is consistently high, varying from 29.2% to 32.1% by mass, which significantly exceeds the maximum permissible limits (3–5%) for fine concrete aggregate (DSTU B V.2.7–30:2013). This is a critical limiting factor for the direct use of screenings in traditional building materials. On the other hand, the chemical composition confirms that the material is a high-quality aluminosilicate raw material, dominated by SiO2 (> 70%) and Al2O3 (14–15%). Such a composition is ideal for obtaining active binders. The originality. For the first time for crushed stone screenings accumulated in the waste dumps of the studied deposits, key physico-mechanical and chemo-mineralogical indicators that determine their resource potential were quantitatively established and documented. The critical limiting factor was quantitatively confirmed – the excess of finely dispersed particles (0–0.63 mm fraction) (29.2–32.1%), which makes the direct use of screenings as a traditional aggregate impossible without preliminary beneficiation. It is scientifically substantiated that the mismatch of physical properties with traditional standards (for concrete and asphalt concrete) does not exclude, but on the contrary, opens up the possibility of its use as an active aluminosilicate precursor (with high SiO2 and Al2O3 content) for the synthesis of innovative geopolymer compositions. Practical implementation. The obtained data on particle size distribution and chemical composition calculations allow for scientifically substantiating the necessity of beneficiation (washing) of the screenings for their use in the traditional construction industry, which will improve the quality of the final product. Furthermore, based on the established chemical composition and high reactivity, the possibility of developing technological regulations for the direct involvement of screenings (without complex beneficiation) in the production of innovative geopolymer binders is substantiated, which will contribute to reducing man-made load and saving natural resources.