Technical and environmental assessment of the incorporation of iron ore tailings in construction clay bricks

Abstract The high production of iron ore in Brazil necessarily leads to the generation of large amounts of waste from the beneficiation stage. The storage of this material in dams is associated not only to environmental problems, but also with the risks related to the safety of the population. The aim of this research was to study a new alternative for reusing high-silicon iron ore tailings, applying them in the red clay ceramic industry. For this, a mixture design of experiments was developed, using three components - the iron ore tailings and two clayey materials – with the respective incorporation ranges: 0%–40% and 30%–70% (by mass). The raw materials were characterized physically, chemically, mineralogically and morphologically. Subsequently, ten mixtures obtained from the experimental design were prepared, and cylindrical specimens were formed by uniaxial pressing. After the firing at 850 °C, 950 °C and 1050 °C, the properties of firing linear shrinkage, bulk density, apparent porosity, water absorption, compressive strength and microstructure behavior of the specimens were assessed. Both the mixture design of experiments and desirability function enabled the determination of an optimal composition which contains 29.1% (by mass) of tailings and which meets the international standards. Next, small-scale construction bricks were produced based on this ideal mixture. The specimens were characterized physically, mechanically and environmentally. The brick has presented 20.94% of water absorption and compressive strength equal to 4.27 MPa, proving its potential to be used in sealing masonry. Besides, its environmental behavior has indicated that the material can be classified as non-hazardous and non-inert, and it is not aggressive to the environment or human health both during and after the useful life. This study has shown that the proposed brick presents advantages from an environmental, economic and technical points of view, contributing to sustainability in the industrial sector and civil construction.