Industrial Waste in Backfill Composite — the Paradigm of Environmental and Process Safety during Field Development

The previous studies of the backfill composite and fill mass did not consider the process of matrix formation. Studying the microstructure of hardened backfill composite allows for conducting its element analysis and investigating the process of matrix formation. The use of industrial waste in backfill composite formula and forming a backfill mass with preset properties is an urgent task. The study aims to investigate the microstructure of hardened backfill composite and the process of its matrix formation. Samples for X-ray diffraction have been ground into a fine powder whereas samples for scanning electron microscopy have been selected from small cubes of approximately 1 cm size. For the microscopic analysis of samples, the Zeiss EVO18 equipment with an energy-dispersive X-ray spectroscopy system has been used. A comparative analysis of mixtures of various formulas has been conducted. It has been proven that limestone and siliceous raw materials as well as C2S participate in the hydration process, whereas their share in the backfill composite reduces during hardening and is consumed to generate hydration products such as tobermorite and CSH gels. It has been established that adding zeolite ZSM-5 in the backfill accelerates the hydration reaction with generation of flake-like tobermorite that fills porous space, which ensures the formation of a denser matrix able to withstand increased loads. The formation of artificial mass based on the backfill composite whose formula includes industrial waste allows for the environmental and technological development of geological resources, which can be possible only based on the principles of comprehensive approach.