Preliminary Study on the Mechanical Activation and High‐Temperature Treatment of Saponite‐Containing Tailings Generated during Kimberlite Ore Dressing

This study investigates transformations of a pre-mechanically activated saponite-containing material with subsequent high-temperature treatment. The thermogravimetric analysis confirmed that the mechanical activation of saponite leads to the destruction of its layered structure, accompanied by the release of silicon dioxide and magnesium oxide in free form. The values of surface activity for mechanically activated saponite-containing material are also calculated. It is shown that when mechanically activated saponite-containing material is mixed with water, minerals of the serpentine group are formed, and further high-temperature treatment leads to the formation of minerals of the olivine group. It is experimentally shown that high-temperature treatment leads to the creation of a more durable structure of the saponite-containing material. This is due to decreased porosity and pore size, and sorption of moisture from the environment is also reduced. The study showed that saponite-containing waste materials can be effectively treated to create composite materials based on magnesia binders. Thus, with this method, the waste is effectively recycled into various green building material and can be used as supplementary cementitious material or fine aggregate replacement in concrete

Comprehensive methodological approach to determine the toxicological characteristics of the highly dispersed rock samples

A schematic diagram of the integrated approach for assessing the toxicological properties of rocks, taking into account their physicochemical properties, was proposed. This methodology was tested on the basalt samples taken from the Myandukha deposit (Arkhangelsk region). The paper presents data of the chemical composition on the basis of which the value of the specific mass energy of atomization of the raw material of the rock was calculated. The energy parameters of the micro- and nanosystems of the sample were calculated: free surface energy and surface activity. To perform toxicological evaluation of the analyzed material a new generation sequencing (NGS) method, the metagenomic analysis, and the MTT method for determining the viability of cell cultures were used. These methods allowed determining species diversity of microorganisms in basalt samples, as well as the cytotoxicity of highly dispersed basalt particles. It was found out that basalt, possessing a high surface activity, is capable of sorbing significant number of microorganisms of different species groups on the surface of the particles, that is a potential danger of microbiological contamination - this fact must be taken into account when processing raw materials in technological processes. At the same time, the non-toxic nature of the basalt nanoparticles was noted. The proposed schematic diagram of the integrated approach can be recommended for assessing the toxicological properties of rocks

Potentiometric method for assessing the pozzolatic activity of highly dispersed materials

ABSTRACT: Introduction. Pozzolatic activity is an important indicator for highly dispersed materials, particularly clay soils. It determines their effective use and characterizes the ability of the active components in their composition to interact with calcium hydroxide. Various methods are employed to assess this pozzolatic activity. Potentiometric methods are effective. They are based on measuring the electrode potential, which is functionally related to the change in the concentration (activity) of calcium ions in the analyzed solutions as the main information parameter of the pozzolatic reaction. The purpose of the research is to test the potentiometric method to assess the pozzolatic activity of highly dispersed materials, as well as the application of suggested approach to determine the rational amount of an active mineral lime-containing additive as a binder component for producing soil-concrete. Materials and Methods. We have chosen clay soil models with different plasticity index and sandy loam of the Arkhangelsk region as the objects. The potentiometric analysis method involved sequentially adding 0.015 mol/l calcium hydroxide solution, in amounts ranging from 0.2 to 0.8 ml, to a suspension containing 0.5 g of soil in 80 ml of distilled water. The potential of the system was measured while continuously stirring at a fixed speed. Results and Discussion. All studied objects are characterized by the pozzolatic activity, which increases in the series sandy loam sandy → clay loam light silty → clay light silty ≈ sandy loam silty and has the order of absolute values coinciding with the literature data. The rational amount of the active mineral lime-containing additive was 1–2% for clay soil models, depending on the plasticity index, and more than 2 % for the sandy loam of the Arkhangelsk region (from the soil mass on dried basis). Conclusion. We have shown the applicability of the potentiometric method of analysis using a calcium-selective electrode to assess the pozzolatic activity of highly dispersed materials on the example of models of clay soils with different plasticity index and sandy loam of the Arkhangelsk regio