The environmental impact of traditional construction materials has led to increasing interest in developing more sustainable alternatives. This study addresses the development of low-carbon autoclaved aerated concrete (AAC) through the complete replacement of ordinary Portland cement (OPC) with ground granulated blast furnace slag (BFS), activated with lime and, in some formulations, supplemented with calcium carbide slag (CCS). Five different AAC mixtures were prepared and evaluated in terms of workability, foaming behavior, compressive strength, phase composition, density, thermal conductivity, and life cycle assessment (LCA). The BFS-based mixtures activated with lime exhibited good workability and foaming stability. After pre-curing, the addition of CCS significantly improved the formation of tobermorite during autoclaving. As a result, the BFS–CCS formulations achieved compressive strengths comparable to the reference OPC-based mix while maintaining low densities (420–441 kg/m³) and thermal conductivities in the range of 0.111–0.119 W/(m·K). These results confirm the technical feasibility of producing structural-grade AAC with a lower environmental footprint.

This research investigates the use of recycled diatomaceous earth (diatomite) from the wine, beer, and oil industries as supplementary cementitious materials in cement-based mixtures. This study aims to reduce embodied energy and promote circular economy practices by incorporating these industrial by-products. The research evaluates the compressive strength, durability, and pozzolanic activity of the mixtures over 7, 28, and 90 days of hydration. The results demonstrate that uncalcined diatoms from wine and oil showed lower compressive strength than natural diatomite, whereas calcination at 500 °C significantly improved performance. Beer diatoms exhibited the lowest mechanical strength because of the organic matter content in their composition. The incorporation of quicklime failed to induce pozzolanic activity in uncalcined diatoms; however, calcination at 500 °C led to improved long-term performance, highlighting the importance of heat treatment for activating diatoms’ pozzolanic properties. This study concludes that recycled diatoms, particularly when calcined, have potential as sustainable cementitious materials.

Reducing the carbon footprint of the construction sector is a growing priority. This study explores the potential of using submerged arc welding (SAW) slag as a precursor in the development of low-carbon geopolymeric materials for 3D printing. The influence of potassium hydroxide (KOH) molarity, partial replacement of ground granulated blast furnace slag (GGBFS) with SAW slag, and water-to-binder (w/b) ratio was evaluated in terms of fresh and hardened properties. Increasing KOH molarity delayed setting times, with the longest delays at 10 M and 12 M. The highest compressive strength (48.5 MPa at 28 days) was achieved at 8 M; higher molarities led to strength losses due to excessive precursor dissolution and increased porosity. GGBFS replacement increased setting times due to its higher Al₂O₃ and MgO content, which slowed geopolymerization. The optimized formulation, containing 20% SAW slag and activated with 8 M KOH at a w/b ratio of 0.29, exhibited good workability, extrudability, and shape retention. This mixture also performed best in 3D printing trials, strong layer adhesion and no segregation, although minor edge irregularities were observed. These results suggest that SAW slag is a promising sustainable material showing for 3D-printed geopolymers, with further optimization of printing parameters needed to enhance surface quality.