The construction industry needs to reduce greenhouse gases, in which cement production is currently responsible for generating between 4% and 6% of the total CO₂ released into the atmosphere. Similarly, many industries produce large amounts of solid waste, which often have low value-added applications or are directly taken to landfills, with consequent negative environmental impacts. One of these industries is the steel industry, which in 2016 generated 18.4 Mt of slag (melting and refining slag) among all European Union countries. In terms of refining steel slag (ladle or white slag), it is estimated that for each ton of steel, between 20 and 30 kg of slag is produced; that is, in 2016, more than 700,000 tons of white slag were generated. It is also known that this material has cementitious properties and can be used as a precursor in alkaline activation processes. Depending on the concentrations used of the activating agent, a higher or lower mechanical performance of the developed materials can be obtained. This work studied the alkali activation of a ladle slag used to manufacture mortars, subjecting them to an initial curing of 24 h at different temperatures (20, 40, and 70 °C). Sodium silicate and sodium hydroxide were used as activating agents, using percentages of Na₂O between 5% and 10% to obtain an optimal dosage of the activator. The physical and mechanical properties of the mortars were evaluated at different ages of curing. In addition, monitoring was undertaken of linear shrinkage due to drying and the mineralogical changes due to activation and curing time.

Cement production is a major contributor to CO₂ emissions, while construction and demolition waste (CDW) presents growing environmental challenges. The new European standard UNE-EN 197-6 permits the use of recycled concrete fines as partial clinker replacements, providing a regulatory framework for integrating CDW into cementitious systems. This study investigates two CDW-derived fillers, FHH (recycled concrete filler) and FHC (recycled ceramic–concrete mixed filler), as partial substitutes for ordinary Portland cement (OPC). The materials were characterized using XRD, XRF, FTIR, and particle size analysis. Cement pastes and mortars with 10%, 20%, and 30% volume replacements were evaluated for hydration behavior, mechanical performance, and durability. At lower replacement levels, FHC promoted ettringite formation and microstructural refinement, while FHH favored carbonate hydrate development; both fillers also exhibited durability comparable to the control. At higher levels, they maintained satisfactory compressive strength. This study offers critical insights into the integration of CDW-derived fillers into cementitious systems, revealing their potential to significantly reduce clinker consumption while maintaining high mechanical and durability standards.

Colquiri is one of several deposits from the Central Andean tin belt, where sphalerite and cassiterite are mined. Although this is a high-grade Zn-Sn deposit, processing results in a low overall yield, with significant amounts of zinc and tin being discarded as tailings. In this study, mineralogical research was conducted to identify the causes of the low yield, so that the flow diagram could be modified to improve recovery. Particle size was measured, and chemical and mineralogical analyses were performed using optical and electron microscopy and X-ray diffraction. The mineral chemistry of the ores was determined using electron probe microanalysis (EPMA), and mineral liberation analyses were performed to complete the characterization. Mineralization occurred in four stages: (1) formation of silicates and oxides; (2) main precipitation of sulfides, including pyrrhotite, sphalerite, and stannite; (3) precipitation of fluorite and the replacement of pyrrhotite by pyrite, which was then replaced by siderite; and (4) weathering of previously formed minerals. The run-of-mine material contains approximately 12 wt.% ZnO and 1.5 wt.% SnO₂. The Zn concentrate contains up to 43.90 wt.% ZnO, and the Sn concentrate contains 52 wt.% SnO₂. The final tailings still retain more than 3–4.5 wt.% ZnO and 1.2 wt.% SnO₂. The average grain size of sphalerite is 200 µm, while that of cassiterite and stannite is 45 µm. The liberated fraction of sphalerite is 51.43%, and binary particles of sphalerite plus stannite account for 60 wt.%. Cassiterite is liberated at 54.68 wt.%. To increase the recovery of sphalerite (with stannite) and cassiterite, as well as the grade of the concentrates, it is necessary to reduce the particle size of the processed ores to less than 100 µm.