The properties and formation mechanisms of eco-friendly brick building materials fabricated from low-silicon iron ore tailings

The volume of tailings discharged worldwide from iron ore smelting processes (i.e., iron ore tailings) has increased dramatically in recent years, and the disposal of this waste poses a substantial ecological threat to soil, and surface and sub-surface water. This threat can be alleviated to a large extent by employing iron ore tailings to fabricate brick building materials, while also effectively meeting the large demand for construction materials. The present paper discusses the preparation of eco-friendly bricks using fine-grained low-silica iron ore tailings and a non-cement curing agent system as the primary raw materials, and a triethanolamine hardening accelerator and a stearic acid emulsion waterproofing agent are also employed as minor components. We first evaluate the effect of the waterproofing agent content on the compressive strength and water resistance of the resulting products. In addition, the phase composition, chemical structure, and microstructure of the products are analyzed via X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy to explore the formation mechanism of the brick products. The analyses demonstrate that hydrated calcium silicate gel and ettringite formed in the curing process are strong binders. The water resistance and compressive strength of the product was optimal when the waterproofing agent and curing agent were 0.3 wt% with an initial curing temperature of 60 °C. The compressive strength and saturated compressive strength of the optimally formed brick products after curing for 28 d were 27.2 MPa and 24.3 MPa, respectively. The other physical properties and durability conform to the Chinese JC/T422-2007 standard for unfired bricks made of tailings.