Environmental-Friendly Mortar Produced with Treated and Untreated Coal Wastes as Cement Replacement Materials

This study aims to examine the influence of untreated coal waste (UCW) and treated coal waste (TCW) as supplementary cementitious materials (SCMs) on the environmental, mechanical, durability, and microstructural characteristics of mortar mixes. UCW preparation procedure consists of sequential steps of crushing and grinding. Afterward, UCW is thermally activated through incinerating at 750°C to be promoted to TCW. Experimental work includes mixing mortar mixtures by partially replacing cement with the coal waste binders (UCW and TCW) at different incorporation levels of 4, 8, 12, and 16% of cement weight. Toxicity characteristic leaching procedure (TCLP) test was applied to investigate the environmental impacts of coal wastes. TCLP test results pointed out that heavy metals including Manganese, Cadmium, Lead, and Chromium could successfully entrap in the cement matrix. The compressive and flexural strengths as mechanical characteristics of mortar mixtures were determined at 3, 7, 28, 90, and 180 curing days. Moreover, the mortar specimens were immersed in 3% sulfuric acid (H2SO4) for 60 and 150 days. Durability results showed that the H2SO4 attack resistance of binary cement mortars containing 4% coal waste binders was better than the plain mortar. Based on the scanning electron microscopy (SEM) images, ettringite was found as the main hydration product of binary cement after 28 days; however, the existence of calcium silicate hydrate (CSH) and calcium hydroxide (Ca(OH)2) in the cement matrix of mixes after 90 days explains the more compact microstructure attained by using coal waste as cement replacement materials compared to control mixtures.

Modeling of the Transition Layer in Ceramic Matrix Composites from Coal Wastes and Clay

A model of the transition layer between the shell and the core of a ceramic matrix composite from coal waste and clay has been developed. The chemical, granulometric and mineral compositions of the beneficiation of carbonaceous mudstones and clay were studied. The technological and ceramic properties of raw materials for the samples manufacturing were determined. The method of manufacturing multilayer ceramic samples from coal waste, clay and their mixture is given. The number of transition layers in the contact zone between the clay shell and the core from coal wastes is determined. The deformation and swelling phenomena of model samples from coal wastes, clay, and their mixtures were revealed at the firing temperature of more than 1000 °C. The formation of a reducing ambient in the center of the sample with insufficient air flow is shown. The influence of the carbonaceous particles amount and the ferrous form iron oxide in the coal wastes on the processes of expansion of multilayer samples during firing has been established.

Studies of the Possibility of Using Coal Mining Waste in Concrete for Mine Construction

The article discusses the possibility of using coal waste for the preparation of mine concrete. As a result of the research, scientific and prac- tical results were obtained. It has been experimentally proved that when a small fraction of coal, which is a waste of coal mining, is added to mine concrete, the strength of concrete decreases, but with a certain ratio of this strength it is sufficient to ensure the required properties. A series of experi- ments was carried out with the addition of liquid glass to the concrete to control the setting time of the mixture. The properties of coal wastes were determined and the possibility of their use in mine concrete was investigated. It has been established that the introduction of a fine fraction of coal in the optimum quantity into the composition of mine concrete is possible without reducing technological parameters.

Technogenic carbonaceous objects of the Chervonohrad mining and industrial district and some technical solutions for their using

Ukraine has significant coal resources. Chervonohrad Mining and Industrial District is the main coal complex in the west of Ukraine. In recent years, the average annual coal production in the mines of Chervonohrad Mining and Industrial District has amounted to 1.5 bn t, coal ash varies over a wide range of 25 to 53 %, average coal ash content of about 40 %. Coal mining has produced millions of tons of coal waste every year. Concentration of technogeneous coal objects (mines, mining infrastructure, coal-mining waste dumps and wastes of coal enrichment) in a relatively small area has caused environmental degradation. Therefore, technological and environmental aspects of carbon-containing technogenic objects are particularly important and actual. Coal-waste dumps in the territory of Chervonohrad Mining and Industrial District are characterized in detail. The dumps cover different areas – from 9–10 to 29–30 ha, the height of the dumps reaches 62 m at the mostly heights of 25–40 m. The total waste deposit in the dumps of existing mines has a volume of more than 20 million m3. The coal wastes from Mezhyrichanskaya mine coal-waste dump was investigated to determine the suitability for thermochemical processing. Technical characteristics of taken coal-waster samples is presented. The technogenic carbonaceous objects and the impact to the environment are evaluated. The developed and patented technical and technological solutions for the technogenic carbonaceous objects using are considered. It is shown that the concept of industrial development of coal wastes dumps is based on two aspects – extraction of valuable mineral components and energy utilization of carbonaceous wastes of coal production. Its patented as Patents of Ukraine technological schemes for terrestrial process in of solid carbonaceous raw material from dumps and sludges with the production of coal tar and synthesis gas CO + H2 are presented, as well as the scheme of a system for utilization of heat from coal dump. Recommendations for the implementation of innovative technologies are based on the results of the laboratory research. The purpose of the resolution is to obtain valuable components and energy from coal wasters while improving the environment.