Investigation of the effects of ferrochrome plant flue dust on portland cement hydration and mechanical properties

Portland cement production is responsible for 5-7% of global carbon dioxide emissions. It is also considered that large quantities of ferrochrome wastes are a significant problem due to the lack of storage areas and environmental impacts, and that environmental and socio-economic benefits can be achieved by using these products as construction materials. For this reason, intensive researches are continuing in cement technology to recycle by-products such as ferrochrome slag and ferrochrome flue dust generated during Ferrochrome production and to reduce carbon dioxide emissions. In this study, the usability of ferrochrome flue dust (FBT) as a supplementary cement material for sustainable cement production is investigated. In the first stage of the study, the physicochemical properties of Portland cement (PC) and FBT were determined using different analysis techniques. In the second stage, 5 types of cement were obtained by substituting FBT into PC at rates of 0%, 2.5%, 5%, 7.5% and 10% by weight. Then, the water requirements, expansion and setting times of the cement pastes prepared with these cements were determined by standard cement tests. In the third stage, reaction products were monitored on the 28th day of hydration by advanced analytical techniques such as X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), simultaneous thermal analysis (DTA/TGA), scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM/EDS). In the final stage, the compressive strengths of the mortars at 1, 2, 7, 28 and 90 days were determined. Microstructure analysis of cement pastes prepared with FBT showed that calcium silicate hydrate (C-S-H), radial fibrous structure of C-S-H, calcium hydrate (CH) and hexagonal etrengite (AFt) crystals formed a compact structure with a heterogeneous distribution. In addition, the fact that FBT is a rich source of MgO as well as aluminosilicate compositions caused an increase in compressive strength at early ages. In conclusion, these data show that economic and ecological benefits can be achieved by using FBT, which causes environmental pollution and health hazards, as a cement substitution material.