Composite materials based on ash and slag waste for thermal insulation of roadbeds

The object of research is the ash and slag mixture of the Amazar boiler station (Trans-Baikal Railway), involved in the composition of the composite as an inert filler of the polymer matrix. The aim of this work is to study the methods of utilization of ash and slag mixture in the compositions of composite materials for waterproofing and thermal insulation of the main platform of the railway roadbed. Method. To obtain data on the chemical and phase composition, physical and physicochemical properties, microstructural features of the ash and slag mixture and the composite based on it, modern analytical methods were used (X-ray fluorescence and X-ray phase analysis; differential scanning calorimetry and thermogravimetry; infrared spectroscopy; light, stereo- and scanning electron microscopy; computed X-ray microtomography, etc.). The conditions for the synthesis of the composite matrix, sample preparation modes and their performance characteristics are presented. Scanning electron microscopy and computed X-ray microtomography were used to study the pore space properties of a composite material and establish the mechanism of its cryostructuring. Results. The ash and slag mixture was found to be non-heaving, with the specific effective activity of natural radionuclides meeting the requirements of GOST 30 108−94 (295 Bq/kg), allowing its unrestricted use in the construction industry. Based on its hydraulic activity, the ash and slag mixture is classified as an inert material. Infrared spectroscopy, differential scanning calorimetry, and thermogravimetry revealed the presence of organic compounds (coal, semi-coke, and coke residues) in the ash and slag mixture. Scanning electron microscopy revealed the heterogeneity of the ash and slag mixture's pore space, which may facilitate the production of a composite with optimal thermal insulation properties. The resulting composite material is frost-resistant and waterproof (ti not less than 3600 s), characterized by a compressive strength of 6.20 MPa and a thermal conductivity of 0.17 W/ (m•K). Cryogenic treatment of the composite material led to a change in the spatial orientation of its microstructural elements. The maximum volume in the composite material structure (13−39 mm³) is occupied by pores with sizes of 0.028−0.084 mm, which account for up to 41%. The total porosity of the composite was 17.28%, which determines its thermophysical properties and allows it to be recommended for the installation of hydro- and thermal-insulating protective layers under railway ballast.

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