This study investigated the potential use of fluorine-containing semiconductor industrial sludge as a mineralizer in Portland cement clinker production. Raw mixes were prepared by partially replacing raw materials with 6%, 9%, and 12% sludge and sintered between 1300 and 1500 °C. The clinker burnability, phase composition, and chemical integrity were evaluated through FreeCaO measurements, X-ray diffraction (XRD) with Rietveld refinement, and X-ray fluorescence (XRF) analyses. The results showed that sludge addition reduced the sintering temperature by up to 150 °C, enabling near-complete clinker formation at 1300 °C for blends containing 9% and 12% sludge (FreeCaO ≤ 0.6 wt.% compared to 62 wt.% in the reference sample). Fluorine incorporation stabilized the re-active β–C₂S polymorph and shifted the alite (C₃S) phase distribution from stable M1 to metastable M3 and T3 phases. Additionally, the C₃A phase content decreased, and a unique fluorine-containing phase, Al₇Ca₆O₁₆F, formed, promoting clinker formation. Lowering the sintering temperature led to energy savings of 15–22.5% and reduced CO₂ emissions by 0.10–0.20 tons per ton of clinker, positively impacting the environment. This study demonstrates that recycling industrial sludge can enhance cement production efficiency and support environmental sustainability.

Hexavalent chromium in Portland cement poses significant health risks and contributes to environmental pollution. Traditional reduction methods rely on costly, resource-intensive reducing agents derived from primary raw materials. This study presents a sustainable approach by synthesising ferrous sulfate from industrial iron-rich sludges and waste sulfuric acid to mitigate hexavalent chromium levels in Portland cement. Three types of iron-rich sludges, sourced from municipal wastewater treatment and steel manufacturing, were analysed using X-ray diffraction to identify their iron-bearing phases. Key parameters, including sludge grinding intensity, stirring rate, reaction time and temperature, were systematically optimised to enhance ferrous sulfate yields. Under optimal conditions, approximately 17 g of pure ferrous sulfate were produced from 10 g of sludge and 50 ml of 20% waste sulfuric acid, achieving a recycling efficiency of around 90%. Incorporating the synthesised ferrous sulfate into ordinary Portland cement reduced hexavalent chromium concentrations below 2 ppm, complying with Environmental Protection Agency, USA standards. This method demonstrates the feasibility of repurposing industrial waste to enhance cement’s environmental performance, offering a promising valorisation pathway for iron-rich sludges and waste acids. The approach is cost-effective and environmentally friendly, aligning with circular economic principles and promoting green innovations in industrial waste management.

The global cement industry emits approximately 2.9 billion tons of greenhouse gases, of which 1.74-1.89 billion tons are emitted from limestone, which is the main raw material for clinkers. Therefore, the feasibility of using slag, a non-carbonated CaO-based raw material, must be investigated, and the physical properties of cement must be considered. In this study, the mixing ratios of the raw mix and properties of cement were analyzed. The CaCO 3 replacement ratio was limited when one type of slag was used; however, when the mixed slag was utilized, the CaCO 3 replacement ratio increased by more than 12 %. The compressive strength of the slag-incorporated cement was lower than that of Ordinary Portland Cement (OPC). Therefore, the lime saturation factor (LSF) of the raw mix and fineness of the cement were increased to improve the compressive strength. The compressive strength of cement with improved fineness was similar to that of OPC for a CaCO 3 replacement ratio of up to 6 %, and it decreased as the CaCO 3 replacement ratio was increased to 9 %. When both fineness and LSF were increased, the compressive strength and flow value of the cement with a CaCO 3 replacement ratio of 12 % were similar to that of OPC.

Clinker production is the main contributor to the environmental footprint of cement manufacturing and represents a key target for improving the sustainability of the cement industry. This study presents a harmonized cradle-to-gate life cycle assessment (LCA) of clinker production based on real industrial plant-level data and establishes environmental benchmarks for inter-plant comparison. The framework enables consistent evaluation of environmental performance while minimizing methodological inconsistencies that often limit the comparability of LCA studies. Using a plant-level industrial inventory dataset, key energy and emission indicators were assessed and compared with a literature-based benchmark under harmonized methodological conditions. The case-study plant exhibited a thermal energy intensity of 3162 MJ/t clinker and electricity consumption of 52.23 kWh/t clinker, representing improvements of approximately 6% and 29%, respectively, relative to the benchmark system. However, total direct CO₂ emissions remained comparable at 1010 kg CO₂/t clinker, indicating that improvements in operational energy efficiency do not necessarily result in proportional reductions in overall greenhouse gas emissions. Process-related emissions from limestone calcination accounted for approximately 73% of total emissions, limiting the mitigation potential achievable through energy efficiency alone. These findings highlight the importance of integrated benchmarking approaches that simultaneously consider energy intensity, emission structure, and climate impact when evaluating clinker production systems and developing decarbonization strategies for the cement industry.

This study investigated the potential use of fluorine-containing semiconductor industrial sludge as a mineralizer in Portland cement clinker production. Raw mixes were prepared by partially replacing raw materials with 6%, 9%, and 12% sludge and sintered between 1300 and 1500 °C. The clinker burnability, phase composition, and chemical integrity were evaluated through Free CaO measurements, X-ray diffraction (XRD) with Rietveld refinement, and X-ray fluorescence (XRF) analyses. The results showed that sludge addition reduced the sintering temperature by up to 150 °C, enabling near-complete clinker formation at 1300 °C for blends containing 9% and 12% sludge (Free CaO ≤ 0.6 wt.% compared to 62 wt.% in the reference sample). Fluorine incorporation stabilized the reactive β–C₂S polymorph and shifted the alite (C₃S) phase distribution from stable M1 to metastable M3 and T3 phases. Additionally, the C₃A phase content decreased, and a unique fluorine-containing phase, Al₇Ca₆O₁₆F, formed, promoting clinker formation. Lowering the sintering temperature led to energy savings of 15–22.5% and reduced CO₂ emissions by 0.10–0.20 tons per ton of clinker, positively impacting the environment. This study demonstrates that recycling industrial sludge can enhance cement production efficiency and support environmental sustainability.