Search Results (303)

To improve traditional cement manufacturing, which generates a large amount of greenhouse gases, blending calcareous green algae and fly ash as cement replacement materials is expected to achieve nearly zero carbon emissions. As a calcareous green alga, Halimeda macroloba is a significant producer of biogenic calcium carbonate (CaCO₃), sequestering approximately 440 kg of carbon dioxide (CO₂) per 1000 kg of CaCO₃, with CaCO₃ production reported in relation to algal biomass. To assess the new low-carbon/low-waste cement production process, the proposed scenarios (2 and 3) are validated via Python-based modeling (Python 3.12) and Aspen Plus^® simulation (Aspen V14). The core technology is the pre-calcination of algae-derived CaCO₃ and fly ash from coal combustion, which are added to a rotary kiln to enhance the proportions of tricalcium silicate (C₃S) and dicalcium silicate (C₂S) for forming the desired silicate phases in clinker. Through the lifecycle assessment (LCA) of all scenarios using SimaPro^® (SimaPro 10.2.0.3), the proposed Scenario 2 achieves the GWP at approximately 0.906 kg CO₂-eq/kg clinker, lower than the conventional cement production process (Scenario 1) by 47%. If coal combustion is replaced by natural gas combustion, the fly ash additive is reduced by 74.5% in the cement replacement materials, but the proposed Scenario 3 achieves the GWP at approximately 0.753 kg CO₂-eq/kg clinker, lower than Scenario 2 by 16.9%. Moreover, the LCA indicators show that Scenario 3 has lower environmental impacts on human health, ecosystem, and resources than Scenario 1 by 24.5%, 60.0% and 68.6%, respectively. Full article

Metakaolin (MK) obtained from calcined kaolinitic clay is a highly reactive pozzolanic ingredient for use as an emerging supplementary cementitious material (SCM) in modern sustainable binder productions. It provides elevated alumina to promote formations of Alumina Ferrite Monosulfate (AFm) and Calcium-Aluminium-Silicate-Hydrate (C-A-S-H) phases, enhancing the chloride binding capacity. However, due to inherent material uncertainty and lack of approach in quantifying hydration kinetics and chloride binding capacity across varied mixes, robustly assessing the chloride resistance of metakaolin-blended concrete remains challenging. In light of this, a machine learning-aided framework that encompasses physics-based material characterisation and ageing modelling is developed to bridge the knowledge gap. Through applying to laboratory experiments, the impacts of uncertainty on the phase assemblage of hydrated system and chloride penetration are quantified. Moreover, the novel Extended Support Vector Regression (XSVR) method is incorporated and verified against a crude Monte Carlo Simulation (MCS) to demonstrate the capability of achieving effective and efficient uncertainty-aware chloride resistance analyses. With the surrogate model established using XSVR, quality control of metakaolin towards durable design optimisation against chloride-laden environments is discussed. It is found that the fineness and purity of adopted metakaolin play important roles. Full article

Vital pulp therapy (VPT) is increasingly recognised as a biologically driven alternative to root canal treatment in teeth with deep caries and a vital pulp diagnosis. Resin-modified calcium silicate-based materials (RM-CSMs) were introduced to combine the bioactivity of traditional cements with improved handling and immediate light-curing, but their biological performance remains debated. Objectives: This systematic review and meta-analysis aimed to evaluate the clinical and radiographic outcomes of VPT performed with RM-CSMs compared with conventional non-resin-modified calcium silicate-based materials (NRM-CSMs) Methods: PRISMA Guidelines were followed to carry out this systematic review. Electronic databases (Medline, Embase, Scopus, and Web of Science) were searched up to October 2025 for randomised clinical trials evaluating indirect pulp capping, direct pulp capping, or pulpotomy. Nine trials met the inclusion criteria. Meta-analyses were performed for TheraCal LC, the only RM-CSM with sufficient clinical evidence. The risk of bias was assessed using the RoB 2 Tool. The certainty of evidence was assessed using GRADE. Results: Pooled results showed no significant differences in overall clinical–radiographic success between RM-CSMs and NRM-CSMs at 90 or 180 days. At 360 days, a trend favouring NRM-CSMs emerged, though not statistically significant. Dentine bridge formation at 360 days was significantly lower with TheraCal LC. Conclusions: Current RM-CSMs demonstrate comparable short-term success to conventional materials but still present biological limitations, particularly regarding long-term reparative outcomes. NRM-CSMs remain the preferred option when maximal bioactivity and predictable dentinogenesis are required Full article

The construction industry faces growing pressure to adopt sustainable materials due to the high CO₂ emissions associated with ordinary Portland cement (OPC) production. Geopolymers synthesized from industrial by-products such as fly ash offer a promising low-carbon alternative. However, the extensive use of commercial sodium silicate (SSC) as an activator remains constrained by its high cost and energy-intensive manufacturing. This study investigates a silica fume-derived sodium silicate alternative (SSA) combined with NaOH as a more sustainable activator for fly ash-based geopolymer mortar. Mortars were prepared with alkali activator-to-precursor (AA/P) ratios of 0.7 and 0.5 and cured at 65 °C and 80 °C. SSA-based mixes exhibited comparable flowability to SSC-based mortars, with slightly longer setting times making them favorable for placement. Mechanical tests showed the superior performance of SSA systems, with AS0.7-65 achieving the highest compressive strength and AS0.7-80 demonstrating greater flexural and tensile strength. Microstructural analyses (SEM, EDX, ATR-FTIR) revealed denser matrices and enhanced sodium aluminosilicate hydrate (N-A-S-H) and calcium-rich N(C)-A-S-H gel formation. Economic assessment indicated approximately 30% cost reduction and a modest (~2%) decrease in CO₂ emissions. These findings highlight SSA as a technically viable and sustainable activator for next-generation geopolymer construction. Full article

The development of effective bone substitutes remains a central goal in regenerative medicine. In this study, lithium-modified bioglass-ceramics based on the 47.5S5 silicate oxide system were synthesized using the sol–gel method, followed by calcination and axial pressing to form cylindrical samples. These materials were sintered at 700 and 800 °C and subsequently examined to evaluate their structural, mechanical, and biological performance. Structural and microstructural analyses confirmed the presence of crystalline phases such as combeite (Na₆Ca₃Si₆O₁₈), NaLiSiO₄, Li₂SiO₃, and calcium silicates, indicating the successful incorporation of lithium within the glass-ceramic network. The bioceramics exhibited improved densification, deformability, and compressive strength with increasing sintering temperature. In vitro degradation in simulated body fluid revealed a consistent increase in mass loss with higher lithium content, suggesting enhanced resorbability linked to lithium oxide. Antibacterial testing indicated moderate antimicrobial activity, with slightly better results observed at higher sintering temperatures. Cell viability assays further supported the materials cytocompatibility. Taken together, these findings suggest that lithium substitution contributes positively to both mechanical robustness and biological behaviour, positioning these ceramics as promising bioresorbable bone substitutes with controlled degradation, suitable for bone tissue engineering where durability, bioactivity, and antimicrobial function are required. Full article

Wood biomass ash (WBA) is a by-product from biofuel energy plants. The disposal of this waste is connected with numerous environmental concerns. A more sustainable choice is to recycle it as a raw material for building and construction materials. However, due to its unstable characteristics, its application in alkali-activated materials (AAM) poses a challenge. One issue is the development of the mechanical properties. To improve them, pozzolanic additives, including coal fly ash (CFA), metakaolin (MK), and natural zeolite (NZ), were added at replacement ratios of 10–40%. Calcium hydroxide, sodium hydroxide, and sodium silicate were used together as ternary activators. The samples were cured at 60 °C for the first 24 h and for the remaining 27 days at room temperature. Mechanical behavior, water absorption, and chemical compositions were examined. The results obtained from XRF were compared with the calculation results of the chemical compositions based on the mix design and oxide compositions of the raw materials. The results show that the respective optimum replacement ratios were 30% CFA, 20% MK, and 20% NZ, with the highest compressive strength corresponding to 22.71, 20.53, and 24.33 MPa, and the highest flexural strength of 4.49, 4.32, and 4.21 MPa. NZ was the most effective in AAM, due to the highest Si/Al ratio in the Ca-rich ambient. Then, CFA contributed less, and MK was the least efficient when used in combination with WBA in AAM. The reduction of Ca/Si ratios in the AAM caused by the pozzolanic additives favors the formation of a binder system made of different hydrates and facilitates the strength enhancement when the Ca/Si ratio is lower than 0.35. Full article

A thorough understanding of the dispersion characteristics of graphene oxide (GO), its micro-pore enhancement mechanisms, and correlations with mechanical properties are crucial for advancing high-strength, durable green concrete. Introducing recycled concrete powder (RCP) can weaken the interfacial transition zone (ITZ) and inhibit hydration reactions, degrading the pore structure and affecting mechanical strength and durability. However, traditional methods struggle to accurately characterize and quantitatively analyze GO-modified pore structures due to their nanoscale size, microstructural diversity, and characterization technique limitations. To address these challenges, this study integrates deep learning-based backscattered electron image analysis with deep Taylor decomposition feature extraction. This innovative method systematically analyzes pore characteristic evolution and the correlation between porosity and mechanical strength. The results indicate that GO promotes Calcium Silicate Hydrate gel growth, refines pores, and reduces pore connectivity, decreasing the maximum pore size by 33.4–45.2%. Using a Convolutional Neural Network architecture, BSE images are efficiently processed and analyzed, achieving an average recognition accuracy of 94.3–96.9%. The optimized degree of GO coating on enhanced regions reaches 30.2%. Fitting porosity with mechanical strength and chloride ion permeability coefficients reveals that enhanced regions exhibit the highest correlation with mechanical strength and durability in regenerated cementitious materials, with R² values ranging from 0.79 to 0.99. The deep learning-assisted pore structure characterization method demonstrates high accuracy and efficiency, providing a critical theoretical basis and data support for performance optimization and engineering applications of recycled cementitious materials. This research expands the application of deep learning in building materials and offers new insights into the relationship between the microstructural and macroscopic properties of recycled cementitious materials. Full article

This paper examined the effect of marble powder (MP) on air-cured cement-based materials when subjected to sulfuric acid (H₂SO₄) attack. Four MP replacement levels were tested: 0%, 5%, 10%, and 15% by weight of cement. The prepared samples were cured for 90 days prior to being exposed to H₂SO₄. Macroscopic tests for apparent density and compressive strength along with microstructural characterization using X-ray diffraction (XRD) and scanning electron microscopy (SEM) were performed to determine the effect of MP on the properties of the materials. The Rietveld method was used to analyze the amounts of different crystalline phases and amorphous calcium silicate hydrate (C-S-H). The obtained results indicate that 5% MP in air-cured cement -based materials exhibited the best behavior with acceptable resistance to acid attacks. This level of MP replacement was found to optimize the filler effect, improve the hydration process, and enhance the matrix density, which in turn reduces the permeability of the material and increases acid resistance. This is attributed to the balanced contribution of MP to phase formation, particularly calcite, which helps to counteract acid-induced dissolution, while also preserving the stability of C-S-H phases. This study provides a new perspective of the role of MP in influencing phase content (crystalline and amorphous phases) and their possible impacts on macroscopic properties such as apparent density and compressive strength. MP behaved as a filler, to improve hydration and resistance to acid attacks. Additionally, using MP as a replacement for ordinary Portland cement (OPC) offers a sustainable alternative by reducing waste and promoting the recycling of marble industry by-products, thereby contributing to environmental sustainability. It is recommended that, 5% MP is the optimal replacement content to enhance durability and mechanical properties in air-cured cement-based materials in aggressive environments, as it is both practical and achievable for infrastructure to be subjected to the aggressive environment. Full article

The consolidation of mural paintings presents a significant challenge for conservators, as the treatments applied must not only be effective but also preserve the aesthetic qualities of the artwork. Ongoing research focuses on developing new products that are more efficient, durable, and compatible with the physicochemical and aesthetic characteristics of the original materials, thereby addressing the limitations of existing consolidants. This study examines two consolidants for mural painting restoration: Estel 1200^® (C.T.S., Madrid, Spain), a commercially available and widely used ethyl silicate-based product, and Nanorepair UV^® (Patent: ES-2766074-B2, Pablo de Olavide University, Seville, Spain), a nanocomposite composed of calcium hydroxide nanoparticles doped with zinc quantum dots. On mortar specimens, prepared according to the Roman fresco technique, the application method for the proposed treatments was optimized. The applicability of the treatments for mural painting conservation was studied by colorimetric measurements and SEM imaging to detect and characterize the formation of surface layers. The effectiveness of the treatments was quantitatively evaluated with tape-peeling cycles. The results show that, although both treatments enhance the consolidation state of mural paintings, Nanorepair UV^® proved to be a more effective consolidant, without altering the aesthetic or physicochemical properties of the artwork. Additionally, this treatment allows for straightforward evaluation of its penetration and enables distinction between treated and untreated areas through the fluorescence of the zinc oxide quantum dots. Full article

Semi-Flexible Pavement (SFP) combines the flexibility of asphalt concrete and the rigidity of cement concrete to provide excellent high-temperature rutting resistance in the summer. However, its application is often limited by the fluidity and mechanical properties of cement-based grouting materials. This study systematically optimized the mix ratios of three types of grouting materials (cement-based, mineral-modified, and polymer-enhanced) using response surface methodology combined with orthogonal tests. The effects of water–binder ratio (W/B), sand–binder ratio (S/B), mineral admixtures and polymer additives on the key properties of grouting materials were systematically studied. By using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD), the evolution of the mixture microstructure and the mechanism of performance change were also analyzed. The test results show that the optimal mix ratio of the cement-based grouting material is W/B = 0.46 and S/B = 0.15; the optimal mix ratio of the mineral grouting material is to replace part of the cement with fly ash (9%), silica fume (6%) and microspheres (3%). Microscopic tests show that fly ash effectively inhibits bleeding; silica fume and fly ash promote the formation of calcium silicate hydrate (C-S-H) gel; microspheres optimize the rheology of the slurry; and the synergistic effect of silica fume and microspheres reduces the internal pores of the grouting material, achieving high fluidity, low bleeding rate and excellent mechanical properties of the grouting material. The polymer-reinforced grouting material is an enhanced slurry formed by adding high-performance water reducer (0.8%), rubber powder (2%) and coupling agent (0.9%) to the optimal mineral grouting material. The combined effect of rubber powder and coupling agent significantly improves the adhesive property between the grouting material and the asphalt interface, making it more suitable for the road performance of SFP in low-temperature environments. Full article

This study presents an analytical and multiscale investigation of the degradation of elastic properties in ordinary Portland cement (OPC) paste subjected to calcium leaching. Eight representative microstructures and three homogenization schemes (Mori–Tanaka, Hashin–Shtrikman, and Voigt) were evaluated to determine the most suitable configuration for predicting stiffness evolution. Model validation against benchmark experimental data at 14 and 56 days demonstrated good agreement, with prediction errors within 10%. Simulation results reveal that progressive decalcification leads to significant reductions in both bulk and shear moduli, with the calcium hydroxide (CH) phase being the most sensitive, followed by low-density (LD) and high-density (HD) calcium silicate hydrate (CSH). The overall stiffness loss increases with the water-to-cement ratio ($w/c$), exceeding 90% at $w/c=0.5$ under complete decalcification. A sensitivity analysis further shows that the rate of modulus degradation decreases with increasing $w/c$, reflecting a mechanical normalization effect rather than improved chemical stability. These findings highlight the dominant role of calcium preservation in maintaining mechanical integrity and provide a robust theoretical framework for predicting the chemo-mechanical degradation and long-term durability of cement-based materials in aggressive environments. Full article

Calcium silicate-based cement is commonly used for bone repair and regeneration. Current research focuses on developing innovative antibacterial materials with radiopacity, which is essential for ensuring successful clinical outcomes in procedures like vertebroplasty and endodontic treatments. Strontium (Sr) has emerged as a powerful additive, stimulating bone formation and inhibiting bone resorption. In this study, we evaluated the impact of varying levels of Sr—5, 10, and 20 mol% (designated as CSSr5, CSSr10, and CSSr20) on critical attributes of bone cement, including radiopacity, setting time, in vitro bioactivity, antibacterial efficacy, and osteogenic activity. The findings indicated that as the Sr content increased, the setting time and radiopacity of the cement increased. Remarkably, the cement formulations containing over 10 mol% Sr achieved radiopacity values surpassing the 3 mm aluminum threshold mandated by ISO 6876:2001 standards. Furthermore, incorporating Sr significantly improved MG63 cell attachment, proliferation, differentiation, and mineralization, while also boosting antibacterial properties in a dose-dependent manner. After 48 h of inoculation with E. coli or S. aureus, the CSSr10 and CSSr20 cements showed a bacteriostatic ratio exceeding 1.7 or 2 times that of the control without Sr. In conclusion, the CSSr10 cement could be a promising bone filler, exhibiting favorable setting time, radiopacity, antibacterial ability, and osteogenic activity. Full article

Premixed bioceramic sealers represent a recent advancement in endodontic obturation, combining bioactivity, moisture-induced mineralization and favorable handling properties. When used with warm gutta-percha techniques, these calcium silicate-based sealers are exposed to elevated temperatures that may influence their physicochemical behavior and interfacial performance. This review aimed to summarize current evidence on premixed bioceramic sealers used in conjunction with thermoplastic obturation techniques. A comprehensive literature search was conducted in PubMed, Scopus, and Web of Science for studies published between January 2020 and July 2025 evaluating the physicochemical properties, bioactivity, sealing ability, fracture resistance, clinical outcomes and retreatability of premixed bioceramic sealers under warm obturation conditions. No meta-analysis was performed—this review provides a narrative synthesis of the available evidence within this scope. Twenty-five studies met the inclusion criteria. In vitro and ex vivo data indicate that premixed bioceramic sealers generally maintain chemical stability and bioactivity when exposed to clinically relevant heating protocols, with favorable dentinal tubule penetration, interfacial adaptation and the formation of calcium silicate hydrate, and hydroxyapatite at the sealer–dentin interface. These characteristics are associated with improved filling homogeneity, potential reinforcement of root dentin and high rates of periapical healing reported in limited short-term clinical studies. However, the evidence also highlights important challenges, including technique-sensitive retreatability, material remnants after re-instrumentation and concerns regarding overextension, and long-term dimensional stability. Within the limitations of predominantly in vitro and short-term clinical evidence, premixed bioceramic sealers used with warm gutta-percha techniques appear to be promising functional materials that combine mechanical sealing with bioactive and mineralizing potential. Standardized protocols and robust long-term clinical studies are needed to confirm their durability, retreatability and prognostic impact in routine endodontic practice. Full article

Background: The bonding compatibility between calcium silicate-based bioceramic cements and restorative materials is critical for long-term success in pediatric dentistry. This study compared the shear bond strength (SBS) of contemporary biointeractive restorative materials to two widely used bioceramics, NeoMTA Plus (NM) and Biodentine (BD). Methods: Eighty acrylic resin blocks with standardized cavities were filled with either NM or BD (n = 40 each) and subdivided into four restorative groups: nanohybrid composite (Filtek Ultimate), giomer (Beautifil II), bioactive restorative (Activa BioActive Restorative), and high-viscosity glass ionomer cement (Fuji IX GP Extra) (n = 10 each). All restorations followed a standardized etch-and-bond protocol. SBS was measured using a universal testing machine, and failure modes were assessed under a stereomicroscope. Data were analyzed using one-way ANOVA and Tukey’s HSD (p < 0.05). Results: BD exhibited significantly higher SBS values than NM (p < 0.001). In the BD group, Filtek Ultimate and Beautifil II achieved the highest and statistically comparable SBS, outperforming Activa BioActive Restorative and Fuji IX GP Extra (p < 0.05). In the NM group, no significant differences were found among materials. Adhesive failures predominated in NM (85%), while BD showed more cohesive failures (50%). Conclusions: Biodentine demonstrated superior bonding stability to restorative materials, with composite resin and giomer performing best. Giomer’s bioactivity and ion release make it a viable alternative to composite resin in suitable clinical contexts. Full article

This study aims to develop a high-performance grouting material for mine goaf backfilling, creating a green and low-carbon cementitious alternative by utilizing coal gangue and sludge as the primary precursors. Based on an orthogonal experimental design, the effects of four factors including the coal gangue/sludge ratio, activator modulus, water–binder ratio, and sodium-to-aluminum ratio on the compressive strength of the geopolymer were systematically investigated. The mineral composition and microstructure of the geopolymer were analyzed using microscopic test methods such as XRD and SEM. The test results indicate that the water–binder ratio has the most significant effect on the polymerization performance of the coal gangue/sludge-based geopolymer (CSG), with compressive strength increasing as the water–binder ratio decreases. The Ca²⁺ provided by the sludge to the reaction system directly promotes the formation of new calcium-containing products such as anorthite and calcium silicate hydrate, which play an important role in improving the strength of geopolymers. Moreover, the developed CSG exhibits a significantly lower carbon footprint compared to conventional cement-based grouting materials, aligning with the goals of sustainable and green construction. When the coal gangue/sludge ratio is 7:3, the water–binder ratio is 0.3, the sodium-to-aluminum ratio is 0.64, and the activator modulus is 1.0, the 3-day compressive strength (CS) of the geopolymer reaches 34.5 MPa, demonstrating its potential as an effective and environmentally friendly grouting material for goaf applications. Full article