Impact on composite performance and CO₂ emissions due to the use of the fine fraction of Iron Ore Tailings

The cement industry can reduce its environmental impact by incorporating Iron Ore Tailings (IOT). This material is generated in large quantities and deposited in piles and dams. IOT is already used as an aggregate in concrete, due to its size grading and chemical composition, and is a viable alternative to produce concrete and other materials. However, the finest fraction of IOT (<0.075 mm) cannot be used as an aggregate. Many researchers have explored IOT as a partial substitute for cement or a mineral addition in concretes and mortars, whether these materials are treated or not, and in conventional or high-strength composites. Although research has evaluated the mechanical and durability properties, there are still no studies that address the environmental impacts of these applications. Thus, this research evaluates cementitious composites under four conditions: without IOT, IOT conventional addition, addition of conventional stone powder, IOT mineral addition in high-performance composites, and partial replacement of cement by IOT with mechanical treatment. Mechanical and carbonation tests were carried out and CO 2 emissions were estimated for the different conditions. It was observed that partial replacement of cement by IOT tends to be the most effective strategy to mitigate the environmental impacts of cement production. However, activation of IOT was not achieved in this study, which resulted in a limited replacement to preserve the desired mechanical properties. The IOT mineral additive contributes to the decrease of natural resource extraction and CO 2 emissions per MPa, demonstrating the effectiveness of this practice in promoting sustainability in the construction sector. The study reinforces the feasibility of using IOT, maintaining or improving material properties, and reducing environmental impacts.