Search Results (256)

The conservation of tuff- and coral rock-built architectural heritage structures (AHS) is challenging because access to original tuff and coral rock has become difficult and severely limited due to urbanization, land reclamation, the depletion of stone quarries, anti-mining and anti-quarrying legislation. An emerging approach to address this issue is to create compatible “replacement” rocks via geopolymerization, a process that is more sustainable and greener than the use of conventional cement and concrete. To explore the potential of geopolymers for AHS conservation strategies, the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were implemented; 103 eligible articles were identified and classified into geopolymers for AHS (34 articles), tuff-built AHS (60 articles), and coral rock-built AHS (9 articles). Tuff substrates in AHSs appear in a variety of colors (yellowish-brown, grayish-cream, reddish-brown, pale greenish-gray and pink hues), densities (1.0–2.5 g/m³), and compressive strengths (3–100 MPa). Meanwhile, coral rock substrates in AHSs appear in whitish-cream color and are coarse-pored (1–5 MPa), fine-grained (8–15 MPa), and calcarenite (50–60 MPa). In terms of geopolymer formulation, metakaolin was reported as the most popular main precursor or admixture, while NaOH and Na₂SiO₃ were used simultaneously as alkaline activators. Aggregates used in geopolymer formulations depended on local availability, including quartz sand, river sand, crushed stones, carbonate stones, volcanic rock, volcanic sand, tuff, brick, ceramic tiles, and waste materials. Aesthetics, chemical composition, physical attributes, and mechanical properties have been identified as key criteria to ensure geopolymer compatibility for AHS conservation application. To date, geopolymers have been applied for AHS conservation as repair mortars, consolidants (i.e., grout and adhesives), and masonry strengthening (i.e., fiber-reinforced mortar). Finally, geopolymers formulated for AHS conservation have similar durability as the original substrate based on accelerated aging tests (i.e., salt mist, wet-dry, and freeze–thaw) and long-term outdoor exposure experiments. Full article

The continuous drive for higher efficiency in gas turbines has led to increased combustion temperatures, making the thermal shock resistance of thermal insulation tiles a critical factor limiting performance. Corundum–mullite multiphase ceramics are widely used in such applications; however, their performance is often constrained by an inherent trade-off between mechanical strength and thermal shock resistance. In this work, a synergistic modification strategy based on rare-earth disilicate phases was developed, wherein Y₂O₃ and SiC were incorporated into a corundum–mullite matrix to enable in situ formation and controlled distribution of Y₂Si₂O₇ via gel casting. During sintering, Y₂Si₂O₇ acts as a transient liquid phase, facilitating densification and grain boundary strengthening; upon thermal shock, it migrates to fill and heal grain boundaries and microcracks, thereby significantly enhancing thermal shock resistance. The optimized sample S5, sintered at 1400 °C, exhibited a bulk density of 2.12 g/cm³ and a bending strength of 68.43 MPa. Notably, after 30 thermal shock cycles (air cooling from 1000 °C to RT), its bending strength increased to 79.71 MPa, corresponding to a 16.48% enhancement. This work provides an effective strategy for incorporating rare-earth disilicates into multiphase ceramics and offers valuable guidance for the development of high-performance components for gas turbines. Full article

This paper presents a method for measuring the spatial distribution of surface normal vectors with high angular accuracy. The measured data are visualized using a color-mapping technique and represented as normal maps, which are commonly used in computer graphics. Reliable methods for evaluating material surface properties have long been sought in industrial applications where visual assessments of reflective properties are still widely employed, particularly in appearance-critical fields. Motivated by this need, we introduce an imaging-based technique for measuring the high-resolution spatial distribution of surface normal vectors from specular reflection. A dedicated measurement apparatus was developed to capture surface normal vectors at 1024 × 1024 sampling points with a spatial resolution of 0.02 × 0.02 mm and an angular resolution of approximately 0.1°. Using this apparatus, normal maps were obtained for various materials, including plastic, ceramic tile, inkjet paper, and aluminum sheets. The spatial distribution of surface normal vectors reflects surface roughness, which strongly influences perceived texture. The resulting normal maps enable not only quantitative surface analysis for industrial inspection but also the physical reproduction of gloss in computer graphics. Full article

This study investigates the feasibility of using brick and ceramic tile waste as aluminosilicate precursors for geopolymer synthesis by analyzing the influence of NaOH concentrations, the Na₂SiO₃/NaOH ratio, and curing methods on the physical and mechanical properties of the resulting matrices. Geopolymer pastes were prepared using NaOH concentrations ranging from 5 to 12 mol/L and Na₂SiO₃/NaOH ratios of 2:1 and 2.5:1. Compressive strength, water absorption, density, and void ratio were evaluated. The results indicate that a combined curing method, consisting of initial curing under dry ambient conditions followed by thermal curing at 60 °C, significantly improved the development of mechanical strength. The brick-based geopolymers reached maximum compressive strengths exceeding 55 MPa at intermediate NaOH concentrations, whereas ceramic tile-based geopolymers required higher alkalinity levels and increased soluble silica content. Overall, the findings confirm that an appropriate combination of precursor type, alkaline activator dosage, and curing conditions enables the formation of geopolymers with denser matrices and enhanced mechanical and physical properties, thereby supporting their potential as a sustainable alternative for the construction industry. Full article

This study presents a comparative evaluation of Environmental Product Declarations (EPDs) within the traditional ceramic industry, emphasizing how differences in data structures, reporting formats, and background databases influence the interpretation of environmental performance. Four product categories—ceramic tiles, sanitary ware, clay bricks, and clay roof tiles—were analyzed using datasets from One Click LCA and the International EPD System. Environmental indicators assessed include fossil-based and total Global Warming Potential (GWP), freshwater consumption, and energy demand, standardized per 1 kg of product. The analysis reveals that discrepancies between platforms arise primarily from the limited level of process-specific information required by current EPD formats, rather than from the platforms themselves. Missing details on raw material composition, firing conditions, and energy sources restrict comparability and hinder the development of robust benchmarks. Furthermore, the study highlights the need for harmonized databases, more transparent PCR requirements, and consistent reporting rules to support meaningful cross-platform comparisons. As the first study to examine EPD data structures for ceramic products across two major reporting systems, it highlights the need to expand product-specific benchmarks and enhance disclosure practices to strengthen the role of EPDs in sustainable market design and climate policy. Full article

The identification of calcareous foraminifera and nannofossils in archaeological ceramics (tiles and bricks from the Archaic to Roman ages) of Naxos and Taormina (Sicily) has, along with other evidence and archaeometric analyses, addressed aspects of technology and raw material source areas. Microfossils, like the other aplastic inclusions, help to interpret ceramic pastes. This paper provides, for northeastern Sicily, a contribution demonstrating the importance of an integrated approach in the study of archaeological ceramics; micropaleontological analysis supports mineralogical, petrographic and chemical data to constrain interpretations of provenance and technology. The preservation of foraminifera calcitic tests and coccoliths is an additional key to identifying errors, failures and strategies during the ancient ceramic firing process. Comparisons with the micropaleontological content of locally outcropping clay deposits have allowed for the unambiguous identification of the clay sources used for ancient ceramic production in the region. Full article

Municipal solid waste incineration (MSWI) fly ash is classified as hazardous waste due to its enrichment of heavy metals and dioxins. This article systematically reviews its generation pathways, physicochemical characteristics, and potential environmental risks, based on the literature from 2010 to 2025 sourced from Web of Science, Scopus, ScienceDirect and China National Knowledge Infrastructure. Emphasis is placed on heavy metal stabilization, dioxin degradation and resource recovery from MSWI fly ash. The mechanisms, technical advantages, and application limitations of three mainstream detoxification, including solidification/stabilization, extraction and thermal treatment, were emphasized. For instance, geopolymer achieves >99.6% Pb immobilization and electrodialytic removal rates of Cd up to 98%, while vitrification reduces the MSWI fly ash volume by >50%. A comprehensive exploration of MSWI fly ash resource utilization was conducted, covering the preparation of ceramic tiles, synthesis of glass ceramic and glass ceramic foams, processing of road substrates, and modification of cement-based composite materials. The current technological system still faces challenges such as high costs, excessive energy consumption, and secondary pollution. Future research should focus on developing green, low-carbon, and low-cost processes, improving long-term environmental stability of products and strengthening pollution source reduction control. Full article

In the high Andean regions of Peru, above 3500 m a.s.l., selecting a roofing system requires balancing budgetary constraints, technical performance, and environmental impacts under severe frost and demanding climatic conditions. This study compared several roofing alternatives from a comprehensive perspective to determine the most suitable solution by simultaneously considering economic, environmental, and social criteria. For this purpose, the Integrated Value Model for Sustainable Assessment (MIVES)—a multi-criteria decision-making methodology—was employed to evaluate five systems: traditional ichu thatched roof (ITR), ceramic tile (CT-II), corrugated galvanized steel with insulation (CGS-II), fiber cement with insulation (FC-II), and sandwich panel with an insulating core (PIR-SP). The model was implemented using a requirements tree with 11 indicators and its stability was assessed through a sensitivity analysis involving five weighting configurations. The overall sustainability indices ranked ITR first (0.697), primarily due to its low carbon footprint and favorable thermal performance. It was followed by CT-II (0.632), due to its superior landscape integration; CGS-II (0.602), owing to its cost-effectiveness; FC-II (0.586), for its balanced environmental profile; and finally, PIR-SP (0.504), which excelled in industrial efficiency and construction speed despite a higher environmental impact. In summary, the results indicated that vernacular solutions minimized environmental impacts and optimized local resources, whereas industrialized options were preferable when durability and assembly times were prioritized. The sensitivity analysis, with variations below 5%, supported the model’s consistency as a decision-support tool and its potential to guide policies for sustainable social housing in high-mountain contexts. Full article

The increasing demand for sustainable construction materials has intensified research on supplementary cementitious materials capable of reducing Portland cement consumption and associated CO₂ emissions. In this context, porcelain polishing residue (PPR), a fine ceramic waste generated by the tile industry, presents potential for valorization in cement-based composites. This study investigates the use of PPR as a supplementary cementitious material in self-compacting concrete (SCC), focusing on its pozzolanic activity and its influence on fresh, physical, and mechanical properties. Pozzolanic behavior was evaluated using strength-based indices with lime and Portland cement, as well as the modified Chapelle method. SCC mixtures were produced with partial replacement of cement by PPR at different levels and assessed in terms of self-compactability, compressive strength, elastic modulus, water absorption, and void index. The results showed that, although PPR did not meet strength-based pozzolanicity criteria at early ages, it exhibited significant calcium hydroxide consumption, indicating latent pozzolanic potential. Fresh-state properties were preserved in all mixtures, and an optimal replacement level of 20% resulted in improved long-term mechanical performance, reduced void content, and enhanced matrix compactness. These findings demonstrate that PPR can be effectively used as a functional supplementary cementitious material in SCC, contributing to more sustainable and eco-efficient concrete production. Full article

Current international standards (EN 12004; SI 4004) are testing ceramic tile adhesives under post-cure thermal aging. However, the standards omit UV radiation exposure during the fresh-adhesive phase. This research investigated three commercial polymer-modified cement adhesives (C2TE, C2TE-S2, C2T) bonding porcelain stoneware tiles under simulated Eastern Mediterranean and desert conditions. Three commercial adhesives were exposed during the initial (uncured) period to elevated temperature (30 °C), humidity variation (40–65% RH), and UV radiation (295–365 nm, 1.5–2.0 mW/cm²) for 20 min, followed by 28 days of curing. Pull-off testing and scanning electron microscopy, combined with quantitative directionality analysis, were used to characterize the mechanical performance and microstructural degradation. UV exposure of adhesives during tiling working time caused a drop of mean bond strength from 1.77 to 0.26 MPa (85% reduction) compared with 1.77 to 0.64 MPa (36% reduction) under hot-arid conditions. Microstructural analysis of the hardened pull-off adhesives revealed that exposure of the fresh adhesive to UV radiation causes thinning and degradation of the interfacial layer (15–40 µm), leading to a drop in macroscopic strength. In contrast, hot-arid exposure induces adhesive bulk cracking while preserving interface integrity. Fracture surface directionality (goodness parameter), crack density, and delamination percentage together distinguish interface failure from adhesive bulk degradation and provide a forecast of long-term durability. This combined SEM-mechanical approach identified critical gaps in testing protocols and enables evidence-based adhesive selection, as current EN 12004 classifications based solely on mechanical properties prove insufficient. Full article

The ceramics industry has long embraced the principles of the circular economy, with a strong focus on the reuse and recovery of raw materials essential to the production cycle. This approach reduces costs by reintroducing secondary raw materials—such as production scraps and recycled materials—into the manufacturing process after appropriate recovery treatments. This study aims to contribute to the transition of the ceramic industry toward a circular economy by incorporating industrial by-products into monoporosa ceramic bodies, thereby transforming waste materials into valuable resources. Monoporosa is a porous, single-fired ceramic wall tile characterized by a high carbonate content and low bulk density. However, the role of secondary raw materials in monoporosa formulations, as well as their influence on processing behavior (e.g., during sintering) and on key technological properties, is not yet fully understood. This work investigates a standard monoporosa formulation based on conventional raw materials (sand, calcite, feldspars, and clays) and compares it with new formulations in which industrial waste materials from local and national sources—originating from other industrial processes—are used as partial or total substitutes for some of the traditional raw materials, particularly sand and calcite. The industrial by-products examined include biomass bottom ash, foundry sand, and marble cutting and processing sludge. All materials were characterized using chemical–mineralogical, thermal, and morphological analyses and were incorporated into the ceramic bodies at different substitution levels (10%, 50%, and 100%) to replace natural raw materials. Their behavior within the mixtures was evaluated to determine ceramic suitability and acceptable replacement ratios. Furthermore, the effects of these additions on water absorption, thermal expansion coefficient, and microstructural characteristics were assessed. Based on the positive results obtained, this study demonstrates the feasibility of using, in particular, two secondary raw materials—foundry sand and marble sludge—in monoporosa body formulations, allowing for the complete replacement of the original raw materials and thereby contributing to the development of more sustainable ceramic compositions. Full article

This paper presents a compact four-beam dual-polarized phased array with the high performance front-end module based on system-in-package (SiP) technology. By employing high-temperature co-fired ceramic (HTCC) substrates, the proposed design achieves efficient thermal management and high level of integration within a tile-type architecture. The front-end module based on SiP can simultaneously generate four independent beams with switchable left- and right-hand circular polarizations, providing flexible beam control. To verify the proposed method, a Ku-band 256-element phased array receiver with four beams has been designed and experimentally verified using HTCC and SiP process. Operating in 14–14.5 GHz, the proposed low-profile array demonstrates stable radiation characteristics, beam pointing accuracy and excellent beam consistency across the entire frequency range. The measurement results confirm that the SiP-based phased array maintains efficient thermal management, high polarization purity and robust beam-scanning capability, validating its suitability for mobile satellite communication. Full article

This study examines the longitudinal shortening of clay blanks during extrusion and introduces a hybrid soft sensor framework for early prediction of ceramic roof tile performance. Targeted properties include shrinkage, water absorption, and saturation. The models integrate real-time process data collected after vacuum extrusion and pressing with clay-specific descriptors such as carbonate content and granulometry, alongside additional variables including moisture, firing temperature, and length reduction. Partial Least Squares (PLS) regression was adopted as the core method due to robustness against multicollinearity and ease of industrial integration. In contrast to complex machine learning pipelines, PLS-based soft sensors enable lightweight edge deployment without reliance on IoT infrastructure. Complementary regression and machine learning models were used to benchmark predictive accuracy and explore nonlinear effects. The results confirm reliable prediction of key performance indicators and reveal mechanistic links between extrusion-induced deformation and downstream behavior. Although developed for clay systems, the framework is generalizable and can be adapted to other traditional ceramic processes or industries seeking interpretable, locally deployable solutions for process control. Full article

Geopolymers are a new breed of construction materials that are environmentally friendly and replace old Portland cement. These materials are produced through the alkaline activation of industrial and agricultural waste rich in aluminosilicates. The growing interest in sustainable building solutions has driven research into their development. Palm oil fuel ash (POFA) and waste ceramic tile powder (WTCP) are both highly rich in reactive aluminosilicates and widely recommended for the production of sustainable geopolymers. This study aims to evaluate the suitability of POFA and WTCP as sustainable alternatives to conventional binders and to identify the potential advantages of each waste material in developing eco-friendly, high-performance geopolymers. The results indicate that specimens prepared with a high content (50 wt%) of POFA or WTCP, incorporating fly ash and slag, can achieve compressive strengths of up to 50 MPa after 28 days of curing. However, increasing the proportion of POFA or WTCP from 50% to 60% and 70% resulted in a significant reduction in compressive strength. In contrast, specimens containing higher proportions of POFA and WTCP demonstrated superior durability when exposed to aggressive environments. In summary, the findings indicate that WTCP is more suitable than POFA for producing geopolymers as eco-friendly construction materials. Its superior reactivity, workability, early-age strength development, and durability make it a promising precursor for sustainable applications in the construction sector. Full article

Portuguese ceramic tile (azulejo) production has evolved significantly since its beginnings in the 16th century. While historic tiles reflect well-established traditional techniques and styles, modern and contemporary works began to explore new aesthetic and material possibilities, introducing textures, surface effects, and experimental approaches that challenge conventional conservation methods. This study examines a contemporary Portuguese tile panel dated from 1987, featuring decorative effect glazes with crater and crazing textures, which were characterized and reproduced. Analytical techniques, including optical microscopy, micro-X-ray fluorescence spectrometry, and Raman spectroscopy in microscopic mode, were employed to characterize material composition and formation mechanisms. Results showed that the crater-effect glazes were achieved with a silica-rich glaze recipe with MnO₂ and ZrO₂. The crazing effect developed in regions where unmelted crystalline silica induced internal stresses within a lead-silicate glaze, contributing to localized degradation. Experimental reproductions of the glazes, guided by analytical data, were conducted to better understand their formation and inform conservation strategies. The results provide essential insights for the technical assessment, documentation, and preservation of contemporary ceramic artworks featuring decorative effect glazes and contribute to the broader field of cultural heritage conservation. Full article