Cement Kiln Research Articles

The influence of cement kiln dust (CK) on alkali-activated concrete is investigated in this work. AAC was produced with the use of alkali activator solutions. The application of an alkaline solution of Na2SiO3 and NaOH depends on the activation of pumice dust (PD) and the beginning of the alkali reaction process in the geopolymer paste. Using varying weight ratios between 0% and 30%, CK was employed as a partial replacement for PD. It also used CK in different weight percentages - 0%, 5%, 10%, 20%, and 30% - as a partial substitute for PD. Workability, compressive strength, porosity, unit weight, and water absorption guided an analysis of AAC's characteristics. The findings indicated that slump flow dropped as CK rates rose. Furthermore, the geopolymer concrete using 30% CK demonstrated a notable 23% improvement in compressive strength at the 90-day test age. Moreover, the samples of geopolymers concrete showed a significant 20% water absorption decrease.

Abstract The increasing global energy demand, the decline in fossil fuels and the growing amount of municipal solid waste are major environmental and socioeconomic issues, calling for advanced techniques to recycle waste into energy. Here, we review the thermochemical valorization of household, industrial and agricultural waste, with focus on municipal solid waste composition, fuel production, fuel characteristics, legislation and standards. Processes include pyrolysis, gasification, and incineration, e.g. in cement kilns. We found that refuse-derived fuel has a calorific value of 8–20 MJ kg −1 , a moisture content of 8–40% and an ash content of 4–20%. Optimized refused-derived fuel pyrolysis can yield up to 67.9 wt% liquid oil, while gasification produces syngas with heating values up to 10.9 MJ m −3 . In cement kilns, co-processing achieves thermal substitution rates of 50–60% in rotary kilns and 80–100% in calciners. Limitations comprise variability in the composition of the feedstock, tar formation and control of emissions.

Integrated resiliency and sustainability assessment of biogeochemical cover system to mitigate landfill gas emissions.

The solid by-product from cement kiln gas installations, known as cement bypass dust (CBPD), is rich in chlorides, which limits the reuse of materials in cement. In this study, three types of CBPD were subjected to an extraction process to obtain a low-chlorine waste material. The relationships between the process parameters, including extraction time (1, 2, 5, 10, and 30 min), temperature (21, 45, and 90 °C), and extraction efficiency, were investigated. The chlorine removal efficiency ranged from 70% to 90%, with the optimal time and temperature identified as 1 min and 21 °C, respectively. Furthermore, a comprehensive characterization of CBPD was conducted before and after the extraction process using X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FT-IR); an approach not yet extensively reported in the literature. The results demonstrated that chloride removal corresponded to an increase in concentrations of Ca, Al, Si, Mg, and Fe oxides in the solid residue. For CBPD samples with initial chloride contents of 13.65% and 15.43%, calcium content in the residue increased by approximately 40%. No linear and predictable relationship was observed between the leaching time or temperature and the release of metals in the solid residue.

Abstract Purpose The construction sector, and in particular concrete, contributes substantially to global emissions, energy demand, and the extensive use of materials. To address these challenges, it is important to develop and implement strategies that reduce the environmental footprint of concrete supply chains. Understanding such impacts and the ways to mitigate them is essential. Therefore, this study focuses on analysing the impacts of decarbonisation strategies within the construction sector, with a specific focus on concrete. Methods A life cycle assessment (LCA) was conducted at different levels of the concrete supply chain, from the production in the United Kingdom (UK) of 1 ton of cement and 1 m3 of concrete to the construction of a building. In addition to the business-as-usual scenario, three alternative scenarios were assessed, namely cleaner electricity, in which the impact of using five different electricity grid mixes was evaluated; cleaner transportation, for which the impact of using battery-powered electric trucks and different transportation distances was assessed; and cleaner fuels, for which the impact of using alternative fuel combinations in the cement kiln was analysed. Multi-objective optimisation was used to find the optimal solution when minimising Global Warming Potential (GWP) and maximising the reduction of all the other impact categories. Results and discussion The results show that significant reductions (of 10 to 37%) in CO2-eq emissions can be achieved when combining different strategies. However, certain strategies could bring an increase in other impact categories, including stratospheric ozone depletion, ionising radiation, freshwater eutrophication, and land use. Conclusions Adopting an electricity mix featuring substantial proportions of nuclear and wind energies, coupled with the use of biomass alongside municipal solid waste for kiln fuel, and integrating battery electric trucks, emerges as a promising alternative. However, this optimal scenario for CO2-eq reduction might not align with the best outcomes across all impact categories. Specific attention is warranted, particularly regarding nuclear sources for electricity and increasing land use due to expanding renewable energy sources.

End-of-Life Management of Creosote-Treated Railroad Ties for Energy Recovery in Cement Kiln Installation: A CFD Modelling Approach

The cement industry accounts for approximately 7–8% of global carbon dioxide (CO2) emissions, primarily due to the energy-intensive clinker production process and reliance on fossil fuels. The environmental impact of this industry is particularly evident in the release of greenhouse gas (GHG) emissions. Therefore, the industry is exploring ways to reduce its energy costs and reliance on traditional fuels and mitigate environmental concerns by using waste-derived materials as a fuel substitute for cement production. In response to increasing environmental pressures, the substitution of fossil fuels with alternative fuels (AF) such as refuse-derived fuel (RDF), biomass, sewage sludge (SS), and used tires has emerged as a viable decarbonization strategy. This paper aims to provide a comprehensive analysis of AFs within the cement industry by reviewing previous studies, focusing on their GHG emissions and the technical, environmental, and economic implications of AFs adoption in cement kilns. A structured literature analysis was employed to evaluate fuel types, heating values, thermal substitution rates, combustion stability, and their effects on clinker quality. Data trends indicate that thermal substitution rates exceeding 80% are achievable with RDF and tire-derived fuels under optimized conditions, while biomass and SS require pretreatment for stable combustion. Environmental assessments report up to 30% reduction in CO₂ emissions and significant decreases in SOx and NOx with proper blending. The review also highlights key gaps in regional adoption and long-term performance evaluations. It concludes by recommending targeted policy support, plant-specific feasibility assessments, and integrated LCA-MCDM frameworks to scale the sustainable use of Afs.

Influence of Admixture on the Properties of Clinker and Its Industrial Assessment in Cement Kiln

An innovative concept of using dust form cement kiln exhaust gases as a component of alkali activator for binder materials

Management of caffeine in wastewater using nanolayered material: An integrated study of process kinetics, modeling, and toxicity assessment.

Soil stabilization has obtained significant attention to overcome challenges associated with weak soils. These efforts focus on improving soil properties, achieving economic benefits, and reducing environmental impacts. This study aims to evaluate the efficiency of using waste or by-product materials to improve the characteristics of subbase layers through chemical stabilization, with a particular focus on reducing construction costs and enhancing structural performance. The methodology included the use of the Cement Kiln Dust (CKD) and ordinary Portland cement (OPC) as chemical stabilizers for two types of subbase materials(Type B and Type C). The percentage of stabilizers for each mixture was 7% by dry weight of subbase; three stabilizer combinations were used: 100% OPC, 100% CKD, and a 50/50 blend of OPC and CKD. Laboratory tests were conducted, including sieve analysis, modified Proctor, California Bearing Ratio , Atterberg limits, and unconfined compressive strength tests to assess the properties of the stabilized soils. The results showed that a mixture of OPC and CKD in equal proportions significantly enhanced the compressive strength of the subbase materials,performance was improved and the required thickness of pavement layers can be decreased, leading to a significant decrease in overall construction cost.

ABSTRACT This paper presents a laboratory study aimed to investigate the effects of three industrial by-products – paper sludge ash (PSA), cement kiln dust (CKD) and bioash (BA) – on the compressibility and consolidation behaviour of two improved clays. These materials were compared to traditional binders, cement and quicklime, using constant rate of strain oedometer tests at 0, 7, 14 and 28 days of curing. Key parameters, including yield stress, pre- and post-yield moduli, and coefficients of permeability and consolidation, were quantified over curing time. Strength followed a logarithmic increase over time, while yield and moduli showed a more linear trend from 7 to 28 days of curing. Compared to the natural clay, the strength and yield stress increased by a factor of 2–18, while the pre-yield modulus and coefficient of variation increased by a factor of 5–102. The experimental data were applied to a serviceability limit state practical design example, demonstrating that at least 50% of traditional binders can be replaced by CKD and BA without significantly affecting compressibility of the improved clay. The findings highlight the potential for reduced climatic impact from soil improvement due to incorporation of by-products binders.

ABSTRACT This study investigated the mechanical, microstructural, and environmental performance of recycled asphalt pavement materials stabilised with ordinary Portland cement (OPC) and cement kiln dust (CKD) as sustainable alternatives for full-depth reclamation (FDR) applications. Unconfined compressive strength (UCS), indirect tensile strength (ITS), flexural strength (FS), resilient modulus (MR), and wet–dry durability were evaluated for various reclaimed asphalt pavement (RAP) blends. Results showed that CKD at 15% maximised strength, the UCS increased up to 9.7 times compared to unstabilised blends and matched 3% OPC in up to 80% RAP blends, with similar ITS, FS, and MR trends before declining at higher dosages. However, CKD mixtures exhibited greater strength loss under wet–dry cycles than OPC mixes. Microstructural analysis revealed cementitious product formation, microstructural densification, elevated chloride/alkali content, and chloro-aluminate hydrates that explain CKD's performance limits. Lifecycle assessment showed CKD can cut CO₂ emissions by up to 89% and reduced costs by 36% versus OPC, supporting its use as a sustainable stabiliser in low- to medium-traffic FDR designs when properly dosed.

The article presents the results of a study on the influence of lightweight aggregates and industrial waste on the physicaland mechanical properties of dry building mixtures (DBMs). The research problem is determined by the need to introduceenvironmentally safe and resource-efficient technologies in modern construction, which requires replacing part of thetraditional mineral components with secondary resources. Perlite, vermiculite, and expanded clay sand were used aslightweight aggregates, while fly ash, granulated blast furnace slag, cement kiln dust, and stone-cutting waste were appliedas industrial by-products. The water-to-binder ratio, bulk density, and compressive strength at 28 days were determined.Regression modeling was employed to establish quantitative relationships between mixture composition and properties. Itwas found that the introduction of perlite or vermiculite in the amount of 10-15% reduces the density by 18-25%, providingthermal insulation properties while maintaining compressive strength at the level of 10-13 MPa.The addition of fly ash in the amount of 20-25% ensures an optimal water-to-binder ratio and improves crack resistance.The combined use of fly ash with stone-cutting waste (5-10%) enhances structure formation and maintains strength at 12-13 MPa. Special attention was given to recycled aggregates obtained from construction and demolition waste. The studydemonstrated that recycled concrete and reinforced concrete meet national standards and allow the production of C16/20class concretes. Therefore, the combination of lightweight aggregates, industrial by-products, and recycled fractionsenables the production of universal DBMs with densities ranging from 1200 to 2300 kg/m³ for various applications – fromfinishing and insulating to structural mixtures. The proposed approach contributes to reducing natural resourceconsumption, lowering production costs, and addressing the problem of construction waste recycling.

Upcycling cement kiln dust for manufacturing clay bricks fired at different temperatures: RSM and ANN-GA hybrid-optimization

Recycling of treated cement kiln bypass dust (T-CBPD) as a new type of supplementary cementitious material (SCM) in calcium sulfoaluminate (CSA) cement

Application of cement kiln dust for the stabilization of expansive soils in the region of Murcia (Spain)

An innovative strategy in wet flue gas denitration technology was proposed to control nitrogen oxide emissions from cement kiln. Here the use of tetrabutylammonium bromide (TBAB) as an additive improved the absorption and utilization efficiency of sulfite absorbents for NO2. Compared with the sulfite solution, the stability time and absorption efficiency of adding TBAB were increased from 25 to 76 min and from 91.2 to 98.4%, respectively. Continuous absorption for 480 min indicated the feasibility of TBAB for repeated use. Moreover, we propose an antioxidant mechanism, including the capture of SO3•- by TBA+, and the reduction of SO3•- by Br-. The successive steps kept the sulfite from the cyclic depletion of the radical chain reaction of "Generate SO3•--Introducing O2-Consuming SO32-" due to O2. A new application of TBAB in free radical trapping and antioxidant is given. Furthermore, a kinetic model describing the macroscopic absorption rate was developed based on different operating conditions.

Abstract In order to improve the properties of refractories for cement kilns, reduce the energy loss in the calcination process of cement kiln. In this work, the anti‐erosion coatings were prepared by the slurry method using alumina as the filler of coating and aluminum–zirconium coupling agent (DH‐550) as additive. The steric effects mechanism of DH‐550 was investigated through Fourier transform infrared spectrometer (FTIR), high‐temperature abrasion resistance tests, and microstructure analysis after erosion. The results show that the substrate without coatings exhibits poor erosion and abrasion resistance. Upon the addition of DH‐550, the hydrolysis of Al2O3 generates an increased density of surface hydroxyl groups, which facilitate the chemisorption of DH‐550 onto the Al2O3 surface, forming a protective organic–inorganic hybrid layer. The grafted DH‐550 molecules introduce steric hindrance effects, thereby effectively increasing interparticle distances and mitigating agglomeration. Consequently, Al2O3 is uniformly distributed on the substrate surface after drying, enabling the formation of 3Al2O3·2SiO2 and Al2TiO5 phases at the interface during the high‐temperature heat treatment. The pores are filled by Al2TiO5 formation, and a dense protective layer is subsequently formed, leading to significantly improved erosion resistance. The overall performance of the sample is optimal when the DH‐550 addition amount is 2 wt%.

This study explores the effectiveness of Cement Kiln Dust (CKD) as a stabilizing agent for black cotton soil to enhance its performance as a subgrade material in road construction. Laboratory experiments were conducted to assess the California Bearing Ratio (CBR) and Unconfined Compressive Strength (UCS) of both untreated and CKD-stabilized soils, with CKD incorporated at varying proportions ranging from 0% to 15%. The results revealed a significant improvement in both CBR and UCS values with increasing CKD content, peaking at 12.5%, where the stabilized soil achieved a CBR ≥ 10% and UCS ≥ 100 kN/m². These enhancements are attributed to pozzolanic reactions, reduction in soil plasticity, and effective void filling facilitated by CKD. However, strength values declined beyond the 12.5% threshold, likely due to excessive fines disrupting particle packing efficiency. The 12.5% CKD mix not only satisfied standard subgrade strength criteria but also exhibited improved durability under saturated conditions, identifying it as the optimal stabilization level. The findings support the use of CKD as a sustainable and cost-effective solution for black cotton soil stabilization. Further research is recommended to assess long-term performance under actual traffic loads and environmental conditions.