Young Jun Lee

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.

The cement industry is one of the largest industrial sources of anthropogenic carbon dioxide (CO2) emissions, with clinker production representing the most energy- and carbon-intensive stage of cement manufacturing. Life cycle assessment (LCA) is widely used to quantify the environmental impacts of clinker production and to support benchmarking of energy use and greenhouse gas emissions. However, plant-level benchmarking studies based on real industrial operational data remain limited, and the relationship between energy efficiency improvements and overall climate change impacts is not always clearly resolved. In this study, the environmental performance of clinker production at a representative integrated cement plant is assessed using a cradle-to-gate LCA approach. The analysis is based on real industrial operational data and uses a functional unit of 1~t of Portland cement clinker. Life cycle inventory data are compiled for raw material inputs, energy consumption, and direct CO2 emissions, and the results are benchmarked against a harmonized literature-based reference dataset. Global warming potential (GWP) is evaluated using IPCC 100-year characterization factors. The results show that the case-study plant exhibits lower thermal energy demand (3162~MJ/t clinker) and electricity consumption (52.23~kWh/t clinker) compared to the literature benchmark. Despite these improvements in energy-related indicators, the total GWP of clinker production at the case-study plant (1010~kg~CO2-eq/t clinker) is comparable to the benchmark value (995~kg~CO2-eq/t clinker). Contribution analysis indicates that process-related CO2 emissions from limestone calcination dominate the total GWP, accounting for approximately 73\% of total emissions. These findings demonstrate that improvements in energy efficiency alone do not necessarily translate into proportional reductions in overall climate change impacts for clinker production. The study highlights the importance of harmonized benchmarking and underscores the need for mitigation strategies that directly address process-related emissions in order to achieve substantial reductions in greenhouse gas emissions in the cement industry.

The utilization of slag-based materials as non-carbonated CaO sources has attracted increasing attention as a strategy to reduce limestone consumption and CO₂ emissions in cement manufacturing. However, compressive strength development in cementitious systems incorporating slag and CaCO₃ replacement is governed by complex interactions among slag chemistry, mixture design, and physical properties, which makes systematic interpretation and prediction challenging. In this study, a structured dataset was compiled from previously published experimental investigations on clinker and cement systems incorporating various slag types and CaCO₃ replacement levels. The dataset integrates slag chemical composition, mixture design parameters, and physical properties with compressive strength measured at 3 and 28 days. Based on observed experimental trends, compressive strength prediction at multiple curing ages was formulated as a multi-output regression problem to explicitly account for the correlated nature of strength development over time. The results reveal clear nonlinear relationships between compressive strength, curing age, and multiple material parameters. Mixed-slag systems generally exhibit higher early-age strength compared to single-slag systems at comparable CaCO₃ replacement levels, while differences among systems become less pronounced at later ages. These findings indicate that compressive strength at different curing ages is interrelated and influenced by shared material characteristics rather than independent variables. Overall, this study provides a data-driven analysis of strength development trends in slag-blended cementitious materials and establishes a consistent literature-based dataset framework suitable for multi-age strength modeling. The proposed approach offers a transparent basis for future predictive modeling and optimization of cement systems incorporating slag-based non-carbonated CaO sources.

The effect of cooling rate on Portland cement clinker was studied using six regimes (2-100 °C/min) after sintering at 1450 °C. X-ray diffraction rietveld refinement and optical analyses revealed that slow cooling stabilized monoclinic-C 3 S and β-C 2 S, while rapid quenching produced triclinic-C 3 S and γ-C 2 S, thereby reducing reactivity. A random forest model was used to predict compressive strength (R 2 = 0.92) based on phase and microstructure data. Moderate cooling (20-50 °C/min) resulted in optimal strength and phase stability. The results indicate that controlled cooling governs clinker reactivity and data driven modeling enables reliable prediction of mechanical performance for sustainable, high-efficiency cement production.

Waste plastic used in domestic cement plant(A~C) were obtained in this study. The properties of waste plastic and clinker using waste plastic were analyzed. The calorific value and thermal decomposition characteristics of waste plastic were analyzed, and the burnability, crystallinity, and microstructure of clinkers were analyzed. The calorific value of waste plastic ranged from 6,400 to 13,500 kcal/kg. The PVC-containing waste plastic from B plant had a relatively low calorific value(approximately 6,400 kcal/kg). The waste plastic did not completely combust at high temperature, and approximately 20 to 30% residues remained. The burnability index of clinker using 3 to 9% waste plastic slightly increased compared to Ref. value. The four major clinker minerals using 3 to 9% waste plastic were detected at similar levels to those of Ref., and the sizes of alite and belite were also similar to those of Ref. It was confirmed that the clinker properties did not change even when using up to 9% waste plastic.

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.

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.

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.

요 약 세계 시멘트 산업의 온실가스 배출량은 매년 증가하고 있으며, 이중 시멘트 클링커 주원료로 사용되는 석회석으로부터 60~65 %가 배 출되고 있다. 이를 해결하기 위해 비탄산 CaO 함유 슬래그를 사용하여 석회석을 대체하는 방안이 검토되고 있다. 본 연구에서는 CaCO3 대체를 위해 2종류의 혼합 슬래그를 사용하였다. 모든 슬래그는 CO2 양이 1 %를 상회하지 않아 대부분 비탄산 CaO로 구성되어 있다는 것을 확인할 수 있었으며, KR 슬래그는 Ca(OH)2가 일부 존재한다고 판단되었다. 혼합 슬래그 사용 혼합원료 배합설계 시 CaCO3 대체율 은 3~12 %로 제어하였으며