Search Results (209)

The cement industry accounts for approximately 7–8% of global CO₂ emissions, primarily due to energy-intensive clinker production and limestone calcination. With cement demand continuing to rise, particularly in emerging economies, decarbonization has become an urgent global challenge. The objective of this study is to systematically map and synthesize existing evidence on technological pathways, policy measures, and economic barriers to four core decarbonization strategies: clinker substitution, energy efficiency, alternative fuels, as well as carbon capture, utilization, and storage (CCUS) in the cement sector, with the goal of identifying practical strategies that can align industry practice with long-term climate goals. A scoping review methodology was adopted, drawing on peer-reviewed journal articles, technical reports, and policy documents to ensure a comprehensive perspective. The results demonstrate that each mitigation pathway is technically feasible but faces substantial real-world constraints. Clinker substitution delivers immediate reduction but is limited by SCM availability/quality, durability qualification, and conservative codes; LC₃ is promising where clay logistics allow. Energy-efficiency measures like waste-heat recovery and advanced controls reduce fuel use but face high capital expenditure, downtime, and diminishing returns in modern plants. Alternative fuels can reduce combustion-related emissions but face challenges of supply chains, technical integration challenges, quality, weak waste-management systems, and regulatory acceptance. CCUS, the most considerable long-term potential, addresses process CO₂ and enables deep reductions, but remains commercially unviable due to current economics, high costs, limited policy support, lack of large-scale deployment, and access to transport and storage. Cross-cutting economic challenges, regulatory gaps, skill shortages, and social resistance including NIMBYism further slow adoption, particularly in low-income regions. This study concludes that a single pathway is insufficient. An integrated portfolio supported by modernized standards, targeted policy incentives, expanded access to SCMs and waste fuels, scaled CCUS investment, and international collaboration is essential to bridge the gap between climate ambition and industrial implementation. Key recommendations include modernizing cement standards to support higher clinker replacement, providing incentives for energy-efficient upgrades, scaling CCUS through joint investment and carbon pricing and expanding access to biomass and waste-derived fuels. Full article

Although substantial knowledge exists regarding the use of ceramic powders as pozzolanic supplementary cementitious materials, a notable gap remains in the literature concerning the durability properties of cement with ceramics. This research aims to address this gap by evaluating the effects of ceramic powders on mortar durability, specifically focusing on resistance to freeze–thaw, high temperatures, and 1% sulphuric acid. The study also investigates the use of recycled ceramic demolition waste as a replacement for calcined clay in limestone calcined clay (LC3) formulations. This research demonstrates the potential of using ceramic waste to enhance mortar durability. The results show significant improvements in freeze–thaw resistance, with strength losses of 1.91% to 2.61% for modified mortars, compared to 6.31% for the reference mortar. Fire resistance also improves, with strength gains of up to 13.9% at 200 °C for LC3 mortars with ceramic powder. At 500 °C, strength losses ranged from 2.8% to 31.9%, with ceramic-containing mortars showing better performance than the reference. At 900 °C, substantial strength losses occurred across all mixes (72.0% to 90.0%), with mortars containing ultrafine ceramic powder showing the best resistance. Resistance to 1% sulphuric acid is enhanced, with strength losses decreasing from 9.37% in the reference mortar to 1.38% in LC3 mortar with ceramic powder. Full article

Supplementary cementitious materials (SCMs) provide a practical solution for reducing greenhouse gas emissions associated with Portland cement production while enhancing the economy, performance, and service life of concrete and mortar. Currently, there is a significant disparity in the availability, supply, and utilisation levels of SCMs worldwide, particularly in South Africa. This paper presents an in-depth analysis of the characteristics and performance of various SCMs, including local availability, factors driving demand, production, and utilisation. The findings indicate that fly ash and limestone calcined clay are the most widely available SCM resources in South Africa, with deposits exceeding 1 billion tonnes each. Fly ash stockpiles continuously increase due to the reliance on coal-fired power plants for 85% of generated electricity and a low fly ash utilisation rate of 7%, significantly below international utilisation levels of 10–98%. Conversely, slag resources are depleting due to the steady decline of local steel production caused by energy and input costs, alongside the growing importation of steel products. Combined, the estimated production of slag and silica fume is about 1.4 million tonnes per annum, leading to their limited availability and utilisation in niche applications such as high-performance concrete and marine environments. Furthermore, 216,450 tonnes of SCM could potentially be processed annually from agricultural waste. In addition to quality, logistics, costs, and other challenges, this quantity can only replace 1.5% of clinker in South Africa, raising concerns about the viability of SCMs from agricultural waste. Based on its findings, this study recommends future research areas to enhance the performance, future availability, and sustainability of SCMs. Full article

Using systematic literature observations, this study explains how 3D printing technology is being applied to innovative sustainable construction (Systematic Literature Review). Additive manufacturing, also referred to as 3D printing technology, has greatly increased productivity and adoption in the building sector. The utilization of eco-friendly materials, enhancing sustainable building practices, and the environmental impact of 3D printing technology in comparison to conventional techniques are the three primary areas of attention for this study. By reducing material waste through additive manufacturing methods, 3D printing technology may employ alternative resources like fly ash, geopolymers, and limestone calcined clay (LC3) cement, which lowers carbon emissions considerably, according to observation data. This technology also speeds up the construction process, saves costs, and enables complex architectural designs that are difficult to achieve with conventional methods. There are still a number of issues, though, such as the high upfront expenditures of supplies and equipment and the long-term robustness of the molded structures that are produced. Nevertheless, 3D printing has enormous potential to transform building methods into more effective and ecologically friendly ones as a result of technological advancements and growing knowledge of desirability. This research provides valuable insights for stakeholders in supporting wider application of this technology to achieve sustainable development goals. Full article

With the increasing global demand for sustainable building materials, coal gangue, as a potential supplementary cementitious material (SCM), has attracted widespread attention. Coal gangue is primarily composed of clay minerals, among which the kaolinite content can significantly enhance its cementitious properties after activation. However, there are various grades of coal gangues, which restrain their application, especially for the low kaolinite content coal gangue. This paper investigates the feasibility of using iron-rich coal gangue with low kaolinite content as a cement substitute through high-temperature activation treatment. In the current study, activated coal gangue replaced cement clinker at proportions of 10%, 15%, and 20%, which was further mixed with limestone powder to form a new cementitious material system. The mechanical attributes of the systems were assessed using compressive strength and microhardness tests. The influence of hydration products and microstructural changes on system performance was further explored through electrochemical impedance spectroscopy (EIS) and quantitative X-ray diffraction (XRD) analysis. The findings suggest that a well-balanced addition of coal gangue can effectively substitute for cement clinker, thereby enhancing both the mechanical properties and microstructure of the systems. These results demonstrate that through appropriate activation treatments, coal gangue can be utilized as an effective SCM. While traditional SCMs like fly ash (FA) and ground granulated blast-furnace slag (GGBFS) have near-zero allocated carbon footprints, their global supply is diminishing and increasingly unreliable. In contrast, our approach valorizes a vast industrial waste stream, aligning with circular economy principles and offering a scalable, sustainable, and low-carbon alternative for the construction industry. Full article

With rapid industrialization, large quantities of industrial solid waste are generated annually. In Panzhihua, China, approximately 300,000 tons of limestone mine dust filter residue (LMDFR) is produced. This study investigates the properties of LMDFR and its potential as a supplementary cementitious material. LMDFR was blended with fly ash (FA) to replace 30% of cement in mortar. Tests were conducted to measure the mortar’s flowability and its compressive and flexural strengths after 7 and 28 days of curing, and XRD, SEM, TG, and DSC analyses were conducted on 28-day specimens. LMDFR primarily comprises ≥95% CaCO₃, with a specific surface area of ~1.3 m²/g and density of 2.694 g/cm³. Mortar flowability increased with LMDFR content, reaching 112.83% when used alone. Flexural strength was largely unaffected, while the 7-day compressive strength significantly improved. However, the 28-day strength decreased when LMDFR was used alone, with a 28-day activity index of 61.10%, compared with 71.52% for FA. A 1:1 blend of LMDFR and FA improved the activity index to 83.18%. Microstructural and thermal results corroborated strength and flowability trends. In conclusion, LMDFR demonstrates promising potential as a supplementary cementitious material in concrete applications. When blended with fly ash at a 1:1 ratio, the composite admixture significantly enhances flowability and early compressive strength while maintaining adequate long-term performance. This synergistic combination not only improves the physical properties of cement mortar but also provides a sustainable solution for the large-scale utilization of industrial solid waste. Full article

The construction industry is responsible for 39% of global CO₂ emissions related to energy use, with cement responsible for 5–8% of it. Limestone calcined clay cement (LC³), a ternary blended binder system, offers a low-carbon alternative by partially substituting clinker with calcined clay and limestone. This study investigated the use of waste clay brick powder (WBP), a waste material, as a source of calcined clay in LC³ formulations, addressing both environmental concerns and SCM scarcity. Two LC³ mixtures containing 15% limestone, 5% gypsum, and either 15% or 30% WBP, corresponding to clinker contents of 65% (LC³-65) or 50% (LC³-50), were evaluated against general purpose (GP) cement mortar. Tests included setting time, flowability, soundness, compressive and flexural strengths, drying shrinkage, isothermal calorimetry, and scanning electron microscopy (SEM). Isothermal calorimetry showed peak heat flow reductions of 26% and 49% for LC³-65 and LC³-50, respectively, indicating a slower reactivity of LC³. The initial and final setting times of the LC³ mixtures were 10–30 min and 30–60 min longer, respectively, due to the slower hydration kinetics caused by the reduced clinker content. Flowability increased in LC³-50, which is attributed to the lower clinker content and higher water availability. At 7 days, LC³-65 retained 98% of the control’s compressive strength, while LC³-50 showed a 47% reduction. At 28 days, the compressive strengths of mixtures LC³-65 and LC³-50 were 7% and 46% lower than the control, with flexural strength reductions being 8% and 40%, respectively. The porosity calculated from the SEM images was found to be 7%, 11%, and 15% in the control, LC³-65, and LC³-50, respectively. Thus, the reduction in strength is attributed to the slower reaction rate and increased porosity associated with the reduced clinker content in LC³ mixtures. However, the results indicate that the performance of LC³-65 was close to that of the control mix, supporting the viability of WBP as a low-carbon partial replacement of clinker in LC³. Full article

This research aimed to evaluate the impact of using brick waste powder (BWP) and varying lengths of polyester fibers (PFs) on the performance properties of asphalt concrete (AC) mixtures. BWP was utilized as a replacement for traditional limestone powder (LS) filler, while PFs of three lengths (3 mm, 8 mm, and 15 mm) were introduced. The study employed the response surface methodology (RSM) for experimental design and analysis of variance (ANOVA) to identify the influence of BWP and PF on the selected performance indicators. These indicators included bulk density, air voids, voids in the mineral aggregate, voids filled with asphalt, Marshall stability, Marshall flow, Marshall quotient, indirect tensile strength, wet tensile strength, and the tensile strength ratio. The findings demonstrated that BWP improved moisture resistance and the mechanical performance of AC mixes. Moreover, incorporating PF alongside BWP further enhanced these properties, resulting in superior overall performance. Using multi-objective optimization through RSM-based empirical models, the study identified the optimal PF length of 5 mm in combination with BWP for achieving the best AC properties. Validation experiments confirmed the accuracy of the predicted results, with an error margin of less than 8%. The study emphasizes the intriguing prospect of BWP and PF as sustainable alternatives for improving the durability, mechanical characteristics, and cost-efficiency of asphalt pavements. Full article

The use of recycled glass powder (RCGP) is investigated as a partial replacement for ground granulated blast furnace slag in blended CEM II/A-LL cements using thermodynamic modelling to simulate cement paste hydration at a water-to-cement (w/c) ratio of 0.5. This study allows a rapid means of examining the likely evolution of these materials over the first two to three years, allowing experimental work to focus on promising formulations. A comparison is made between the evolving solid phase and solution chemistries of four materials: a standard Portland-limestone (CEM II/A-LL), a ‘control’ blend, comprising equal quantities of CEM II/A-LL with GGBS and two novel blended cements containing RCGP. These represent 15% replacement (by mass) of GGBS by RCGP blended with either 40% or 60% CEM II/A-LL. The simulations were performed using the code HYDCEM, a cement hydration simulator, which calls on the thermodynamic model PHREEQC to sequentially simulate the evolution of the four cements. The results suggest that partial replacement of GGBS by 15% RCGP results in no significant change in system chemistry. The partial replacement of cementitious slag by waste container glass provides a route by which this material can be diverted from the landfill inventory, and the mass-balance and energy balance implications will be reported elsewhere. Full article

Flotation tailings (FT), as a product of the exploitation and processing of copper ore, represent a significant environmental and health risk due to the high content of heavy metals and sulfide compounds. Contemporary concepts of sustainable development and circular economy increasingly emphasize the need for rational use of resources and minimization of all types of waste, including mining waste. In this context, the reuse of flotation tailings in the construction industry represents a significant step towards closing the material flow in the mining and construction sectors. In order to reduce the negative impact of FT on the environment, the possibility of its application as a substitute for a portion of cement in the production of concrete was investigated. The main challenge is to reduce the negative impact of sulfides, originating from sulfide compounds, in order to achieve the desired concrete quality. Limestone aggregates of different size fractions (0/4, 4/8, 8/16 mm) were used for sulfide neutralization. Pyrite concentrate was used as a sulfide source, which together with FT provides the mixtures FT-7, FT-14, FT-25, and FT-40, with sulfur contents of 7.56, 13.84, 25.02, and 39.82%, respectively. FT mixtures were used as a substitute for Portland cement (PC) in the preparation of concrete. Test methods included XRD (X-ray diffraction), XRF (X-ray fluorescence), SEM (scanning electron microscopy), LP (leaching procedure), TCLP (toxicity characterization leaching procedure), assessment of acid eluate generation potential (AP—acid potential, NP—neutralization potential, and NNP—net neutralization potential), NEN (determination of heavy metals in cured concrete eluate), and UCS (uniaxial compressive strength of cured concrete). The results showed that the chemical characteristics of FT, as well as the chemical and mechanical properties of hardened concrete, allow the efficient use of these tailings in concrete mixes, which significantly utilizes FT, reduces the generation of mining waste, and contributes to the reduction of the negative impact on the environment and achieving sustainable development in mining. Full article

It has been proven that silica fume (SF), which is a by-product from the manufacturing of single-crystal silicon, is beneficial for enhancing the mechanical properties, durability, and workability of geopolymers, as it can be quickly dissolved and form silicate-based cementitious phases in alkaline environments. However, the reinforcement mechanism of SF on geopolymer remains unclear due to the chemical complexity of geopolymer and the variety of SF types. Additionally, the solubility of calcite in an alkali environment is quite limited, and thus the formation of the amorphous calcium-based gels will be thwarted due to the lack of soluble calcium ions. Most importantly, with the development of the single-crystal industry, the amorphous silica content, crystallinity, and trace elements of SF itself have changed, which blocks the understanding of the activation mechanism of geopolymers combined with SF and insoluble calcite. To unveil the underlying modification mechanisms of SF on geopolymer materials along with insoluble calcite, in this study, two types of SF were used as the fly ash replacement in a fly ash/limestone system to prepare geopolymer materials. The reinforcement effect significantly depends on the SF types even with similar particle size and chemical compositions. The results indicate that the mechanical properties of geopolymer materials modified with SFs are not only governed by the ratio and contents of Si, Ca, Al, and Mg in SFs but also depend on the crystallinity and activity of the SFs. The hydration products could be varied according to the reaction environment. The research results not only contribute to the optimization design and application of geopolymer materials but also pave new pathways for the upcycling use of solid wastes such as SF, low-grade fly ash, or even other aluminosilicate solid wastes to achieve sustainable development. Full article

The study identified the optimal material, e.g., raw composition and moisture content, and process parameters for the non-pressure agglomeration of carbonate lime combined with biomass waste, e.g., calcium sulfate (ECO-ZEC), post-production residue (PPR), and fly ash using a molasses-based binder. The chemical analysis revealed that the CaO content in the granules ranged from 34% to 52%, with the highest calcium concentration observed in formulations containing carbonate limestone. Among the waste-based additives, PPR exhibited a calcium content only 7% lower than that of pure carbonate lime, whereas ECO-ZEC and fly ash contained 20% and 30% less calcium, respectively. Due to the low MgO levels in the tested granules, they cannot be classified as calcium–magnesium fertilizers. Regarding heavy metal content, concentrations of cadmium and lead remained below the permissible regulatory limits. The highest levels of these elements were detected in the fly ash-enriched granules, consistent with the known chemical composition of this waste type. The tested waste materials ECO-ZEC, PPR, and fly ash demonstrated alkaline pH values ranging from 12.37 for fly ash and 12.28 for PPR to 8.84 for ECO-ZEC. The reference carbonate lime showed a slightly lower pH of 8.82. Mechanical strength testing indicated that the addition of PPR improved the mechanical resistance of the granules compared to the reference sample. Conversely, the inclusion of ECO-ZEC and fly ash reduced this parameter. Notably, granules containing fly ash and PPR exhibited prolonged disintegration times in water, suggesting their potential application as slow-release fertilizers. The findings of this study demonstrate that industrial waste materials generated from biomass combustion can serve as effective components in the production of innovative lime-based fertilizers. This innovative approach not only promotes the recycling of by-products but also supports the development of sustainable agriculture by reducing the environmental burdens associated with waste disposal and encouraging resource efficiency. Full article

In this study, high-belite Portland cement clinker was successfully prepared by using low-grade limestone and solid-waste calcium carbide slag and steel slag, achieving resource utilization while reducing CO₂ emissions caused by raw materials decomposition in the cement industry. Using X-ray diffraction, microscopic images, thermogravimetric analysis, and differential scanning calorimetry, the physicochemical reaction process, phase composition, and microscopy of clinker were studied. The results indicated that the high-belite Portland cement clinker can be successfully produced at 1340 °C for 1 h with a belite content of 58.6% and an alite content of 24.2% when the composition of raw material was suitable. Meanwhile, the content of high-reactive-phase α-C₂S can reach 1.4%. Via microscopic viewing, C₂S and C₃S were interphase distributed and well developed. In this study, the CO₂ emission of the prepared high-belite Portland cement clinker was 54.67% lower than that of ordinary Portland cement clinker. All the above results confirm that high-belite Portland cement clinker can be produced using low-grade limestone and solid wastes, which can significantly reduce CO₂ emission during Portland clinker production and promote an innovative approach to the cement industry. Full article

In response to the need for sustainable soil stabilization alternatives, this study explores the use of waste materials and biopolymers to improve the mechanical behavior of clay from Cartagena, Colombia. Crushed limestone waste (CLW), ground glass powder (GG), recycled gypsum (GY), xanthan gum (XG), and the combination of XG with polypropylene fibers (XG–PPF) were used as stabilizing agents. Samples were compacted at different dry densities and cured for 28 days. Unconfined compressive strength (UCS) and ultrasonic pulse velocity (UPV) tests were conducted to assess the strength and stiffness of the treated mixtures. Results were normalized using the porosity/binder index ($\mathrm{\eta }/B_{iv}$), leading to predictive equations with high determination coefficients (R² = 0.94 for UCS and R² = 0.96 for stiffness). However, XG-treated mixtures exhibited distinct behavior that prevented their inclusion in a unified predictive model, as the fitted exponent x in the porosity/binder index ($\mathrm{\eta }/B_{iv}^x$) differed markedly from the others. While an exponent of 0.28 was suitable for blends with mineral binders, the optimal x values for XG and XG–PPF mixtures were significantly lower at 0.02 and 0.03, respectively, reflecting their unique gel-like and fiber-reinforced characteristics. The analysis of variance (ANOVA) identified cement content and compaction density as the most influential factors, while some interactions involving the residues were not statistically significant, despite aligning with experimental trends. The findings support the technical viability of using sustainable additives to enhance soil properties with reduced environmental impact. Full article

This study investigated the technical feasibility and antimicrobial potential of incorporating ornamental rock, limestone, and ginger waste into coating mortars with the aim of developing an innovative and sustainable solution for civil construction. This study evaluated the synergistic action of these materials on the microbiological and mechanical resistance of mortar, contributing to the greater durability and efficiency of the coatings. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) analyses were performed to characterize the morphology, chemical composition, and crystalline structure of the added materials, confirming their suitability for the cement matrix. Tests in the fresh state evaluated parameters such as density, consistency index, and entrained air content, demonstrating the viability of the formulations, whereas flexural and compressive strength tests indicated significant improvements in the mechanical performance of the modified mortar. Microbiological tests demonstrated a significant reduction in microbial colonization, indicating the action of ginger’s bioactive compounds, such as gingerol and shogaol, which have antimicrobial properties and are effective in inhibiting the growth of pathogenic microorganisms, as confirmed by the reduction in the bacterial colony count from 4 × 10² to 1 × 10² CFU mL⁻¹. Comparisons with conventional compositions indicate that the proposed approach outperformed traditional formulations in terms of both mechanical resistance and microbiological control. Thus, the results validate this research as a promising strategy for improving the durability and performance of coating mortars, reducing maintenance costs, and promoting the sustainable use of alternative materials in civil construction. Full article