Search Results (71)

Due to their biocompatibility, biodegradability, injectability, and self-setting properties, calcium–magnesium phosphate cements (MCPCs) have proven to be effective biomaterials for bone defect filling. Two types of MCPC powders based on the magnesium whitlockite or stanfieldite phases with MgO with different magnesium contents (20 and 60%) were synthesised. The effects of magnesium ions (Mg²⁺) on functional properties such as setting time, temperature, mechanical strength, injectability, cohesion, and in vitro degradation kinetics, as well as cytocompatibility in the MG-63 cell line and the osteogenic differentiation of BM hMSCs in vitro, were analysed. The introduction of NaHA into the cement liquid results in an increase in injectability of up to 83%, provides a compressive strength of up to 22 MPa, and shows a reasonable setting time of about 20 min without an exothermic reaction. These cements had the ability to support MG-63 cell adhesion, proliferation, and spread and the osteogenic differentiation of BM hMSCs in vitro, stimulating ALPL, SP7, and RUNX2 gene expression and ALPL production. The combination of the studied physicochemical and biological properties of the developed cement compositions characterises them as bioactive, cytocompatible, and promising biomaterials for bone defect reconstruction. Full article

New methods for real-time materials phase identification based upon focal construct tomography (FCT) have been examined. Such quantitative assessment has significant potential in sectors where in-line analysis is required, including screening within aviation security. As a recent component of work programs developing FCT, its capability for accurate, quantitative analysis has been assessed for the first time. Diffraction signatures from mixed-phase materials were acquired from an energy-dispersive FCT system running under normal operational conditions. A calibration curve was constructed from the spectra and subsequently employed to assess the composition of ‘blind’ samples. The results demonstrated that this approach was able to precisely predict the polymorphic phase composition of samples to ±5 wt%. Conclusions: The potential impact of these findings is significant and will enable applications of FCT beyond those requiring a phase identification to those necessitating quantification, such as counterfeit medicines, pharmaceutical quality assurance, aging of explosives, and cement production. Full article

Amid growing environmental concerns and the increasing demand for sustainable construction practices, the exploration of alternative materials in building applications has garnered significant attention. This paper provides a comprehensive review of the use of agricultural waste as an aggregate in cementitious composites, with a particular focus on palm kernel shells, coconut shells, hazelnut, peanut and pistachio shells, stone fruit shells and pits, date and grape seeds, rice husks, maize (corn) cobs, and sunflower seed shells. For each type of agro-waste, the paper discusses key physical and mechanical properties, global production volumes, and primary countries of origin. Furthermore, it offers an in-depth analysis of existing research on the incorporation of these materials into cement-based composites, highlighting both the advantages and limitations of their use. Although the integration of agro-waste into construction materials presents certain challenges, the vast quantities of agricultural residues generated globally underscore the urgency and potential of their reuse. In line with circular economy principles, this review advocates for the valorization of agro-waste through innovative and sustainable applications within the construction industry. Full article

As part of this study, mechanical property tests were carried out at different stages with different curing temperatures to elucidate the effect of temperature on the mechanical properties of concrete. The curing temperatures were laboratory curing temperature (standard curing at 20 °C) and variable temperature curing (simulated site ambient temperature curing) according to the actual temperature of previous construction sites. The compressive strength, split tensile strength, axial tensile strength, and modulus of elasticity values were tested, and the growth rates were calculated. According to previous experiments, the maturity indexes under two kinds of maintenance conditions were calculated based on the N-S maturity formula, F-P equivalent age calculation formula, and D-L equivalent age calculation formula proposed by the maturity theory. Moreover, logarithmic function, exponential function, and hyperbolic function fitting were carried out using the fitting software to study the developmental relationship between strength and maturity. The physical phase analysis of low-heat cement was performed using XRD and simultaneous thermal analysis, and pore structure analysis was conducted using the mercuric pressure method (MIP). We also conducted an SEM analysis of hydration products and the micromorphology of low-heat cement with 25% fly ash. Energetic spectroscopy analyzed the elemental content. In this study, it was found that temperature has a significant effect on the mechanical properties of concrete, with temperature having the greatest effect on splitting tensile strength. The strength of low-heat silicate cement concrete increases with maturity. The highest correlation coefficient was based on the hyperbolic function fit in the F-P equivalent age. The improved development of concrete strength in the later stages of the two curing conditions in this test indicates that low-heat cement is suitable for use in hydraulic tunnels. The low-heat cement generates a large number of C-S-H gels via C₂S in the late stage, filling the internal pores, strengthening the concrete densification to make the structure more stable, guaranteeing the late development of concrete strength, and imparting a micro-expansive effect, which is effective for long-term crack resistance in hydraulic lining structures. Full article

The research presented in this article seeks to identify the possible causes of reinforcement shadows (RS) on the surface of concrete test specimen produced under laboratory conditions. Different hypotheses about RS were selected based on factory practices and simulated in the study. The test specimens were cast horizontally in contact with steel form-facing surfaces coated with a water-soluble release agent. In addition, two scenarios were analysed during specimen production: reinforcing mesh was fixed using plastic spacers or tie wire. The analysis of the reinforcement shadows was based on visual inspection, taking photos, surface moisture content measurements, and colour variation analysis using the Natural Colour System. It was concluded that RS, which are typically characterized by darker lines, can be defined by the percentage of black colour present in the shadowed area compared to the percentage of black colour in the surrounding area. This percentage can be quickly assessed on a factory scale using digital colour readers that provide timely information. The reduced concrete cover thickness from 35 mm to 10 mm revealed light horizontal dark lines on the exposed surface. It was hypothesised that the gap of less than 10 mm between the reinforcing bars and the steel form-facing plate, along with the sieving effect of the fresh concrete, can retard the cement paste hydration process, resulting in unhydrated ferrite phases that contribute to the dark colour of the unhydrated cement. The release agent sprayed on the steel form-facing surface straight through the reinforcing mesh created a RS effect of the reinforcement on the exposed concrete surface. The absence of a release agent under steel rebars decreased the wettability at the interface between the formwork and fresh concrete, resulting in dark lines during the curing process. It is important to avoid such cases when manufacturing precast reinforced concrete elements. Quantitatively assessing RS and proposing a standardized method for calculation and categorization could be a new research direction in the future. Full article

Sustainable energy consumption in cement production involves practises and strategies aimed at reducing energy use and minimising environmental impact. The efficiency of a cement kiln is dependent on the kiln design, fuel type, and operating temperature. In this study, a dynamic simulation analysis is used to investigate heat losses and distribution within kilns with the aim of improving energy efficiency in cement production. This study used Computational Fluid Dynamics (CFD) with Conjugate Heat Transfer, Turbulent Flow, and the Realisable k−ϵ turbulence model to simulate heat transfer within the refractory and wall systems of the kiln, evaluate the effectiveness of these systems in managing heat losses, and establish the relationship between the heat transfer coefficient (HTC) and the velocities of solid and gas phases. The simulation results indicate that a temperature gradient from the kiln’s interior to its exterior is highly dependent on the effectiveness of refractory lining in absorbing and reducing heat transfer to the outer walls. The results also confirm that different thermal profiles exist for clinker and fuel gases, with clinker temperatures consistently peaking at approximately 1450 °C, an essential condition for optimal cement-phase formation. The results also indicate that phase velocities significantly influence heat absorption and transfer. Lower velocities, such as 0.2 m/s, lead to increased heat absorption, but also elevate heat losses due to prolonged exposure. The relationship between the heat transfer coefficient (HTC) and the velocities of solid and gas phases also indicates that higher velocities improve HTC and enhance overall heat transfer efficiency, reducing energy demand. Full article

Energy-intensive enterprises (EIEs), as vital demand-side flexibility resources, can significantly enhance the power system’s ability to regulate demand by participating in demand response (DR). This helps alleviate supply pressures during tight demand–supply conditions, ensuring the system’s safe and stable operation. However, due to the current level of electricity management in EIEs, their participation in demand response has disrupted the continuity of production to some extent, which may hinder the sustainability of demand-side management mechanisms. To address this issue, this paper proposes a two-stage distributionally robust optimization (DRO) model for managing production electricity in EIEs, considering multiple uncertainties. First, a production electricity load model based on the state task network (STN) is developed, reflecting the characteristics of industrial production lines. Next, a two-stage DRO model for day-ahead and intra-day electricity management is formulated, integrating an uncertainty set for distributed generation output based on the Wasserstein distance and probabilistic constraints for the day-ahead DR capacity. Finally, a cement plant in western China is used as a case study to validate the effectiveness of the proposed model. The results show that the proposed model effectively guides EIE in participating in DR while optimizing electricity costs, enabling cost savings of up to 27.7%. Full article

Supplementary cementitious materials (SCMs), such as fly ash, slag, and silica fume, predominantly derived from industrial waste, are widely utilized in concrete due to their proven ability to enhance both its mechanical and durability properties. Moreover, these SCMs play a crucial role in mitigating the carbon footprint of concrete by reducing its cement content, which is responsible for approximately 8% of global CO₂ emissions. However, the sustainability and long-term availability of conventional SCMs are increasingly under scrutiny, particularly in light of the impending shutdown of coal-fired power plants, which threatens the future supply of fly ash. As a result, the concrete industry faces an urgent need to identify alternative SCMs to maintain and advance eco-friendly practices. This article stands out from previous reviews by employing a bibliometric analysis to comprehensively explore the use of commonly utilized agricultural ashes (rice husk, palm oil, and sugarcane bagasse), prevalent in tropical and subtropical regions as SCMs. Additionally, it provides valuable insights into the potential of cold-weather crops (e.g., barley, canola, and oat) that demonstrate promising pozzolanic reactivity. The study critically evaluates and compares the physical and chemical characteristics of agricultural ashes from both hot and cold climates, assessing their influence on the fresh, mechanical, and durability properties of concrete. It also addresses the challenges and limitations associated with their use. Furthermore, in line with the United Nations and Environmental Protection Agency (EPA) sustainability goals, the review evaluates the environmental benefits of using agricultural ashes, emphasizing waste reduction, resource conservation, and energy savings. This comprehensive review paper should deepen the understanding of agricultural ashes as sustainable SCMs, providing a strategic direction for the construction industry to adopt low-carbon concrete solutions across various climates while promoting advancements in production methods, performance standards, and emerging technologies such as hybrid materials and 3D printing. Full article

Cement-bonded particle boards are gaining popularity globally due to their durability, strength, and, more importantly, environmental sustainability. The increasing demand for these materials has also created the necessity for the sustainable recycling of these materials. In this study, the potential to recycle wood-wool cement board (WWCB) waste into new lightweight insulation biocomposite material was examined. The waste WWCBs were crushed and separated into a fine aggregate fraction, and WWCB production line residues were also collected and compared. The crushed WWCBs were used to produce biocomposites with various compaction ratios and different binder-to-aggregate ratios. To improve their thermal properties and reduce their density, hemp shives were used to partially replace the recycled WWCB aggregate. Their physical, mechanical (compressive and flexural strength), and thermal properties were evaluated, and the drying process of the biocomposites was characterized. The results showed that the density of the produced biocomposites ranged from 390 to 510 kg/m³. The reduction in density was limited due to the presence of cement particles in the aggregate. The incorporation of hemp shives allowed us to reduce the density below 200 kg/m³. The thermal conductivity of the biocomposites ranged from 0.054 to 0.084 W/(mK), placing the material within the effective range of natural biocomposites. This research has demonstrated that industrially produced WWCBs can be successfully recycled to produce sustainable lightweight cement-bonded insulation materials. Full article

Biomass ash is currently attracting the attention of science and industry as an inexhaustible eco-friendly alternative to pozzolans traditionally used in commercial cement manufacture (fly ash, silica fume, natural/calcined pozzolan). This paper explores a new line of research into Marabou weed ash (MA), an alternative to better-known conventional agro-industry waste materials (rice husk, bagasse cane, bamboo, forest waste, etc.) produced in Cuba from an invasive plant harvested as biomass for bioenergy production. The study entailed full characterization of MA using a variety of instrumental techniques, analysis of pozzolanic reactivity in the pozzolan/lime system, and, finally its influence on the physical and mechanical properties of binary pastes and mortars containing 10% and 20% MA replacement content. The results indicate that MA has a very low acid oxide content and a high loss on ignition (30%) and K₂O content (6.9%), which produces medium–low pozzolanic activity. Despite an observed increase in the blended mortars’ total and capillary water absorption capacity and electrical resistivity and a loss in mechanical strength approximately equivalent to the replacement percentage, the 10% and 20% MA blended cements meet the regulatory chemical, physical, and mechanical requirements specified. Marabou weed ash is therefore a viable future supplementary cementitious material. Full article

Calcined clays (CCs) as supplementary cementitious materials (SCMs) can be a promising option to reduce clinker content and CO₂ emissions in eco-friendly concretes. Although CCs as components of composite cements in combination with Ordinary Portland Cement (OPC) and limestone powder (LSP) have attracted industry interest, their use as concrete additives is limited. This study investigates the effects of the addition of CCs on the fresh and hardened properties of industry-standard ready-mixed concretes. Four concrete mix designs, each with three superplasticizer dosages, were tested, resulting in 12 variations. The CCs used, which are typical of 2:1 bentonite clays with low metakaolin content, reflect the clays available in Germany. The results showed that CCs significantly influenced the workability, which could be controlled with a high superplasticizer dosage. Increased CC contents reduced bleeding tendencies, which was beneficial for certain structural applications. Early age strength decreased with CCs, but the 28-day strength exceeded that of pure OPC concretes up to 30 wt% CCs. Resistance to CO₂-induced carbonation decreased with higher levels of CCs but was comparable up to 15 wt%. Freeze–thaw damage decreased, and chloride migration resistance improved due to a denser microstructure. The global warming potential (GWP) of the concretes tested is in line with that reported in the literature for concretes made from highly blended cements, suggesting that CCs can improve the sustainability of concrete production. Full article

The use of fly ash in compositions as a substitute for a part of cement is economically favorable and ecologically feasible in connection with large accumulations of waste at the enterprises of the energy sector. In addition, the technology of cement production provides high-temperature treatment of mineral substances in kilns with significant emissions of carbon dioxide. One of the most effective directions of the utilization of fly ash is their use in concrete composites. The use of this material will provide the required temperature and humidity conditions in residential premises, solve the problem of “cold bridges” in structures, minimize heat losses of the structure, and increase the energy efficiency of buildings in general. At the same time, polystyrene concrete, due to its structural structure and the presence of thermally conductive concrete, has limited opportunities for thermal and physical–mechanical properties. To improve the operational properties of polystyrene concrete, it is proposed to use composite binders, including fly ash from the thermal power station of Astana. The main aim of this study is to develop compositions of polystyrene concrete with reduced thermal conductivity and improved physical and mechanical properties. The objectives of this study include the determination of characteristics of fly ash from Astana, formulation of polystyrene concrete mixtures with different proportions of fly ash, and evaluation of their thermal conductivity properties. These tasks are in line with the objectives of the ISO 50001 standard to improve energy efficiency and reduce environmental impact. The results showed that the addition of fly ash from Astana to polystyrene concrete leads to a marked reduction in thermal conductivity, contributing to improved energy efficiency of the building envelope. Optimal results were achieved by using 15% of Astana fly ash as an additive in polystyrene concrete, which led to a significant reduction in thermal conductivity of 51.47%. This reduction is in line with improving the energy efficiency of building materials, especially in cold climates. Full article

Addressing the current lining cracking problem in coastal tunnels, this paper independently introduces a novel type of repair material for tunnel lining cracks—the composite repair material consisting of waterborne epoxy resin and ultrafine cement (referred to as EC composite repair material). Through indoor testing, we have analyzed the change rule of the mass change rate, compressive strength, flexural strength, and chloride ion concentration of the repair material samples in erosive environments, with the dosage of each component in the EC composite repair material being varied. We have also investigated the working performance, mechanical properties, and microstructure of the repair material. The results of this study show that when the proportion of each component of ultrafine cement, waterborne epoxy resin, waterborne epoxy curing agent, waterborne polyurethane, defoamer, and water is 100:50:50:2.5:0.5:30, the performance of the EC composite repair material in a chloride ion-rich environment is optimal in all aspects. When the mixing ratio of each component of the EC composite repair material is as stated above, the repair material exhibits the best performance in a chloride ion erosion environment. With this ratio of components in the EC composite repair material, the fluidity, setting time, compressive strength, flexural strength, and bond strength of the repair material in a chloride ion erosion environment can meet the requirements of relevant specifications, and it is highly effective in repairing tunnel lining cracks. The polymeric film formed by the reaction between the waterborne epoxy resin emulsion and the curing agent fills the pores between the hydration products, resulting in a densely packed internal structure of EC composite repair material with enhanced erosion resistance, making it very suitable for repairing cracks in tunnel linings in erosive environments. Full article

The global momentum towards hydrogen has led to various initiatives aimed at harnessing hydrogen’s potential. In particular, low-carbon hydrogen is recognized for its crucial role in reducing greenhouse gas emissions across hard-to-abate sectors such as steel, cement and heavy-duty transport. This study focuses on the presentation of all hydrogen-related financing initiatives in Italy, providing a comprehensive overview of the various activities and their geographical locations. The examined funding comes from the National Recovery and Resilience Plan (PNRR), from projects directly funded through the Important Projects of Common European Interest (IPCEI) and from several initiatives supported by private companies or other funding sources (hydrogen valleys). Specific calls for proposals within the PNRR initiative outline the allocation of funds, focusing on hydrogen production in brownfield areas (52 expected hydrogen production plants by 2026), hydrogen use in hard-to-abate sectors and the establishment of hydrogen refuelling stations for both road (48 refuelling stations by 2026) and railway transport (10 hydrogen-based railway lines). A detailed description of the funded initiatives (150 in total) is presented, encompassing their geographical location, typology and size (when available), as well as the funding they have received. This overview sheds light on regions prioritising decarbonisation efforts in heavy-duty transport, especially along cross-border commercial routes, as evident in northern Italy. Conversely, some regions concentrate more on local transport, typically buses, or on the industrial sector, primarily steel and chemical industries. Additionally, the study presents initiatives aimed at strengthening the national manufacturing capacity for hydrogen-related technologies, alongside new regulatory and incentive schemes for hydrogen. The ultimate goal of this analysis is to foster connections among existing and planned projects, stimulate new initiatives along the entire hydrogen value chain, raise an awareness of hydrogen among stakeholders and promote cooperation and international competitiveness. Full article

Geopolymers have been proposed as a green alternative to Portland cement with lowered carbon footprints. In this work, a geopolymeric mortar obtained using waste materials is studied. Fly ash, a waste generated by coal combustion, is used as one of the precursors, and waste glass as lightweight aggregates (LWAs) to improve the thermal performance of the mortar. The experimental study investigates the effect of varying the alkali activating solution (AAS) amount on the workability, compressive strength, and thermal conductivity of the mortar. Indeed, AAS represents the most expensive component in geopolymer production and is the highest contributor to the environmental footprint of these materials. This research starts by observing that LWA absorbs part of the activating solution during mixing, suggesting that only a portion of the solution effectively causes the geopolymerization reactions, the remaining part wetting the aggregates. Three mixes were investigated to clarify these aspects: a reference mix with a solution content calibrated to have a plastic consistency and two others with the activating solution reduced by the amount absorbed by aggregates. In these cases, the reduced workability was solved by adding the aggregates in a saturated surface dry state in one mix and free water in the other. The experimental results evidenced that free water addiction in place of a certain amount of the solution may be an efficient way to improve thermal performance without compromising the resistance of the mortar. The maximum compressive strength reached by the mortars was about 10 MPa at 48 days, a value in line with those of repair mortars. Another finding of the experimental research is that UPV was used to follow the curing stages of materials. Indeed, the instrument was sensitive to microstructural changes in the mortars with time. The field of reference of the research is the rehabilitation of existing buildings, as the geopolymeric mortars were designed for thermal and structural retrofitting. Full article