Mechanical behavior, petrography and microstructural analysis of mining waste recycled bricks

Over the past decades, the mining industry has come to be considered as a material resource for sustainable development programs. Mining wastes are used as raw material in civil construction, minimizing the environmental impacts of waste disposal. However, the addition of these new materials requires in-depth studies on their behavior. This paper aims to study the mechanical behavior, petrography and microstructural analysis of mining waste recycled bricks produced in a full-scale research on sustainability in civil construction. Mechanical tests (compaction, compressive, and tensile strengths) were carried out. A petrographic examination according to international standards was conducted. Complementary scanning electron microscopy and energy-dispersive X-ray spectroscopy analysis were performed. Mechanical tests showed that the addition of red mud can improve compressive strength by over 10% while the addition of fly ash does not show any improvement on the compressive strength. The petrographic characterization showed minerals thermally altered due to the temperatures reached in the brick manufacturing process and isotropic matrix showing glassy materials. The textural homogeneity (well-dispersed grains in a compact matrix) in the thin sections studied could explain the improvement on the geotechnical behavior of the bricks. Similar considerations can be obtained analyzing the geometry and quantity of pores.