Search Results (81)

This systematic research was conducted as the first comprehensive scientific analysis of ancient lime plaster samples from Anuradhapura, a World Heritage Site in Sri Lanka. Five ancient heritage sites from 1st to 10th Century AD, covering two stupa domes: Abhayagiri (AP01) and Jethavana (AP02), Monk residence building near Ruwanweliseya Stupa (AP03), Deeghapashan Rock Shelter Building of Abhayagiri Monastery Complex (AP04), and Vessagiriya Rock Shelter wall lime Plaster (AP05) were examined by employing Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray fluorescence (XRF), thermogravimetric analysis (TGA), optical microscopy (OM), scanning electron microscopy (SEM) and gas chromatography-mass spectrometry (GC-MS). The current work investigated the composition, mineralogical and microstructural properties, binding media, and organic additives. Our findings indicate that calcareous lime from seashells and river sand are the main raw materials, with ratios of 1:2.7, 1:2.0, 1:2.4, 1:4.4, and 1:3.7 for the AP01, AP02, AP03, AP04, and AP05 samples, respectively. Data also suggest that plant-based materials, mainly wood apple wax, along with nanoscale fibrous materials, were used as the main additives to enhance the properties of lime plasters. This study provides insights into the raw materials, their mixing ratios, and the techniques employed in the lime plastering of ancient Anuradhapura City, and serves as a scientific reference for the conservation and restoration of ancient buildings resilient to climate change. Full article

From an environmental perspective, the use of clam shells contributes positively to marine waste management and promotes more sustainable construction practices. This study aims to analyze the influence of clam shell-derived filler on the mechanical properties of cementitious mortars, evaluating its effect as a function of dosage and particle fineness, in order to determine its potential as a sustainable additive in construction applications. The shells were ground for 0.5, 1.0, and 1.5 h and incorporated at percentages ranging from 0.5% to 5.0% by mass of cement. Slump (reduced Abram’s cone) was performed in the fresh state for each specimen mixture, while flexural strength, and compressive strength tests were performed at 7, 14, and 28 days of curing. Microstructural characterization was also performed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) analysis. In addition, particle size distribution parameters were determined to quantify the effect of grinding time on particle refinement and its relationship with mechanical performance. A multifactor ANOVA was conducted to evaluate the statistical significance of grinding time and filler dosage on compressive strength. The results showed that the combination of 0.5 h of grinding and 1.0% filler provided the best mechanical performance for both flexural and compressive strength, with values of 7.27 MPa and 26.16 MPa, respectively. Dosages higher than 2.0% tended to decrease strength, which is associated with saturation of non-cementing particles. EDX analysis showed adequate calcium distribution without generating chemical segregation. The results showed that the combination of 0.5 h of grinding and 1.0% filler provided the best mechanical performance for both flexural and compressive strength, with values of 7.27 MPa and 26.16 MPa, respectively. Dosages higher than 2.0% tended to decrease strength, which is associated with saturation effects and increased specific surface area. The statistical analysis confirmed that both grinding time and filler dosage significantly influence compressive strength, highlighting the importance of optimizing particle size distribution and filler content to achieve improved mechanical performance. Full article

In this work, the propagation of acoustic waves in shell trumpets is explored, and the overtones generated by them are studied. We consider different shell geometries, for which their particular morphology is taken into account. This impacts the fundamental frequencies as well as the overtones. An analytical model based on differential equations is developed to predict these overtones and compared with real recordings of some shell trumpets belonging to several collections in Mexico (experimental results). As a consequence, the notes of archaeological shells that cannot be played due to their physical damage are estimated. Full article

This study conducts systematic experimental and numerical investigations to address the parameter calibration issue in the discrete element model of seashells, aiming to establish a high-fidelity numerical model that accurately characterizes their macroscopic mechanical behavior, thereby providing a basis for optimizing parameters of seashell crushing equipment. Firstly, intrinsic parameters of seashells were determined through physical experiments: density of 2.2 kg/m³, Poisson’s ratio of 0.26, shear modulus of 1.57 × 10⁸ Pa, and elastic modulus of 6.5 × 10¹⁰ Pa. Subsequently, contact parameters between seashells and between seashells and 304 stainless steel, including static friction coefficient, rolling friction coefficient, and coefficient of restitution, were obtained via the inclined plane method and impact tests. The reliability of these contact parameters was validated by the angle of repose test, with a relative error of 5.1% between simulation and measured results. Based on this, using ultimate load as the response indicator, the PlackettBurman experimental design was employed to identify normal stiffness per unit area and tangential stiffness per unit area as the primary influencing parameters. The Bonding model parameters were then precisely calibrated through the steepest ascent test and design, resulting in an optimal parameter set. The error between simulation results and physical experiments was only 3.8%, demonstrating the high reliability and accuracy of the established model and parameter calibration methodology. Full article

Refractory geopolymers derived from aluminosilicate sources and alkaline activation are a promising alternative to traditional fired bricks, particularly when low-cost, waste-derived raw materials are used. This study improves the workability of a refractory brick formulated with clays (Kaolin and Tepozan–Bauwer), seashell waste, sodium silicate, potassium hydroxide, and water by incorporating sodium lignosulfonate (LS) and polycarboxylate (PC) plasticizers. Clays from Comonfort, Guanajuato, Mexico, and seashells were ground and sieved to pass a 100 Tyler mesh. A base mixture was prepared and evaluated using the Mini Slump Test, varying plasticizer content from 0 to 2% relative to the solid fraction. Based on workability, 0.5% LS and 1% PC (by solids) increased the slump, and a blended plasticizer formulation (1.5% by solids, 80%PC+20%LS) produced the highest workability. These additives act through different mechanisms, with LS primarily promoting electrostatic repulsion and PC steric repulsion. Bricks with and without plasticizers exhibited thermal resistance up to 1200 °C. After four calcination cycles, compressive strength values were 354.74 kg_f/cm² for the brick without plasticizer, 597.25 kg_f/cm² for 1% PC, 433.63 kg_f/cm² for 0.5% LS, and 519.05 kg_f/cm² for 1.5% of the 80%PC+20%LS blend. Strength was consistent with changes in porosity and apparent density, and 1% PC provided a favorable combination of high workability and high compressive strength after cycling. Because the cost of clays and seashells is negligible, formulation selection was based on plasticizer cost per brick. Although 1% PC and the 1.5% of 80%PC+20%LS blend showed statistically comparable strength after cycling, 1% PC was selected as the preferred option due to its lower additive cost ($0.0449 per brick) compared with the blend ($0.0633 per brick). Stereoscopic microscopy indicated pore closure after calcination with no visible cracking, and SEM–EDS identified O, Si, and Al as the significant elements, with traces of S and K. Overall, the study provides an integrated assessment of workability, multi-cycle calcination, microstructure, and performance for refractory bricks produced from readily available clays and seashell waste. Full article

Valorization of environmental waste into sustainable energy and value-added products offers a strategic pathway for advancing circular economic development and resource sustainability. In this study, waste cooking oil was converted into biodiesel using biogenically generated CaO, prepared thermally at 900 °C. The reaction process was modeled and optimized with a Taguchi orthogonal array L9(3⁴), considering four factors at three levels to yield nine experimental conditions. The model reliability was statistically validated through analysis of variance (ANOVA) at 95% confidence level (p < 0.05), achieving a high determination coefficient (R²) of 0.9965. The maximum biodiesel yield of 91.08% was obtained under the optimal conditions of the methanol to oil ratio of 15:1, a catalyst loading of 4.5 wt%, a reaction time of 90 min, a temperature of 65 °C, and a constant stirring speed of 650 rpm. The fuel property analysis confirmed compliance with international biodiesel and diesel standards). Economic evaluation of the process showed that integrating waste cooking oil with reusable seashell-derived catalysts enabled the production of high-quality biodiesel at R23.20 (~USD 1.39)/L, highlighting a sustainable and cost-competitive alternative to conventional feedstock. The study contributes to advancing waste-to-energy technologies and supports the transition towards a circular and sustainable energy future. Full article

The present experimental study was set up to examine the use of waste seashells (ground to powder form) to replace cement partially and as a filler material in concrete. Two distinct particle size ranges of seashell powder were adopted based on their intended function: 63–125 micron particles are used as a filler to enhance packing density, and 0–63 micron particles are used as a cement replacement to improve reactivity. Four concrete mixes, including a control mix, were designed, with ground seashell powder used to replace cement, both as a filler replacing 15% of the cement and additionally as finer seashell powder replacing 0, 15, and 30% of cement (labelled S0F15, S15F15, and S30F15, respectively). The seashells’ chemical, physical, and mineralogical properties were characterised using particle size analysis through sieving, X-ray diffraction (XRD), Scanning Electron microscopy (SEM), and pH test methods. Furthermore, the fresh properties of concrete, such as initial and final setting time, were studied. The hardened seashell-based concrete was subjected to direct compressive strength, bulk density, and modulus of elasticity analysis. The results showed that the 28-day compressive strength of concrete with seashells was moderately reduced by nearly 25% compared to the control mix. In the case of modulus of elasticity, the reductions were about 5%, 7% and 13% for mixes S0F15, S15F15 and S30F15, respectively, compared to the control mix CM. Finally, the carbon emission from concrete with 15% and 30% seashell powder content as cement replacement (plus 15% cement replaced with the powder acting as a filler in both cases) resulted in a notably lower carbon emission of 250 and 212 kg CO₂ e/m³, respectively, compared to the control mix, with a reduction of approximately 24%. This is a sizable reduction in Global Warming Potential (GWP) value. Therefore, the study concluded that the investigated seashell powder in concrete could benefit an eco-friendly environment and conservation of natural resources. Full article

The aquaculture industry generates large amounts of shell waste, with limited recycling options at the industrial scale. This study explores the feasibility of substituting 20% of gypsum with seashell waste to produce sustainable, fire-resistant panels for non-load-bearing walls on a semi-industrial scale (2.4 × 2.2 × 0.1 m). The new composite exhibits high density (≈1500 kg/m³) and mechanical performance comparable to commercial gypsum. Thermal and fire tests confirmed its excellent insulation and stability: after 4 h of standard fire exposure, the non-exposed surface temperature remained below 80 °C, meeting European fire-resistance criteria. The incorporation of shell waste slightly reduced density and thermal conductivity (0.23 W/mK at 500 °C) without affecting strength or surface hardness. Environmental characterization revealed leaching and radionuclide levels well below regulatory limits, confirming its safety for building use. Overall, this work demonstrates, for the first time at a semi-industrial scale, the technical and environmental feasibility of reusing seashell waste as a gypsum substitute for fireproof materials. The proposed approach advances circular-economy strategies for aquaculture residues, providing an innovative pathway toward sustainable and low-impact construction products. Full article

This paper explores the structural, mechanical, thermal, and electrochemical properties of copper matrix composites (CMCs) enhanced by Crassostrea madrasensis seashell powder, which were produced via powder metallurgy and resistance sintering. FESEM images showed a uniform distribution of bio-ceramic particles in the copper matrix composites (CMCs), leading to an improved microstructure and enhanced mechanical behavior. Mechanical tests showed that after incorporating 12 wt.% seashell powder, the average hardness increased to 56 HV, and compressive strength improved to 686 MPa. Density analysis showed a decrease in porosity, which was attributed to better particle diffusion during sintering. The corrosion resistance was evaluated using electrochemical techniques, including OCPT, Tafel polarization, EIS, LSV, and chronocoulometry, which were employed in 3.5 wt.% NaCl media with varying concentrations of the extract of Allium sativum (garlic) as a green inhibitor. Garlic-derived phytochemicals facilitated surface passivation, which was proven by shifts in potential, reduced corrosion rates, and minor charge transfer. The findings confirm that Crassostrea madrasensis bio-ceramic reinforcements and garlic extract-based corrosion inhibition provide a sustainable method for improving the performance and durability of copper matrix composites. Full article

This paper presents a systematic literature review of articles that include a life cycle assessment and sustainability assessment to measure the potential impacts of seashell waste usage in concrete production, the geographical context, and existing knowledge gaps. Concrete’s extensive production has significant environmental impacts due to resource depletion and ecosystem threats. Sustainable alternatives, like seashell waste, are explored, with life cycle assessment and sustainability analysis aiding in evaluating their environmental performance and promoting circular economy principles. Following PRISMA guidelines, a comprehensive review of eco-concrete with seashell waste was conducted. Search strategies were refined to include related terms, and rigorous screening processes were employed for article selection and data extraction. A literature search yielded 66 articles on seashell waste in concrete, with 33 selected for review through initial and secondary screenings of studies. Studies primarily focused on seashells as an aggregate or cement substitute. Findings indicate that seashell waste as a construction material has been studied to a limited extent, with few studies utilizing life cycle assessment tools. However, some existing quantitative and qualitative sustainability analyses suggest seashell waste could be a promising and sustainable option for construction materials. Geographically, Spain leads in research, with China and Iran also prominent. Furthermore, we conducted a content analysis using Leximancer software to identify and evaluate concept maps through current research domains and emerging trends. Life cycle assessment, environment, and sustainability are common themes among the articles studied. This review also identifies limitations in bias, article heterogeneity, and search scope. Opportunities exist for a circular economy approach in cement production using seashell waste, but future research should explore its economic, environmental, and social impacts. Recommendations include expanding life cycle assessment studies, improving sustainability analyses, and using tools like the Integrated value model for sustainable evaluation. Full article

Processed sea sand has emerged as a viable alternative to traditional fine aggregates in the Sri Lankan construction industry. Despite its economic and environmental advantages, concerns over residual seashell content have limited its widespread adoption by local contractors. Residual seashell content, typically ranging from 1% to 3% after processing, has raised concerns about its impact on the performance of concrete. This study systematically investigates the influence of seashell fragments, with a content of up to 5%, on the fresh, mechanical, and durability properties of sea sand concrete and mortar. Experimental results indicate that workability remains stable, with minor variations across the tested range of shell content. Compressive strength remains relatively consistent from 0% to 5% seashells, indicating that seashell content does not significantly impact the strength within this range. Durability tests reveal minimal effects of shell content on concrete performance within the tested shell range, as indicated by results for water absorption, rapid chloride penetration, and acid exposure testing. Accelerated corrosion indicates that the typical shell content does not increase corrosion risk; however, high shell content (>3%) can compromise corrosion durability. Overall, these findings demonstrate that the mechanical and durability performance of sea sand concrete remains uncompromised at typical seashell content levels (1–3%), supporting the use of processed sea sand as a sustainable and viable alternative to traditional fine aggregates in Sri Lankan construction. Full article

This study presents the fabrication and characterization of sustainable polylactic acid (PLA)-based biocomposites reinforced with bio-origin fillers derived from food waste: seashells, eggshells, walnut shells, and spent coffee grounds. All fillers were introduced at 15 wt% into a commercial PLA matrix modified with a compatibilizer to improve interfacial adhesion. Mechanical properties (tensile, flexural, and impact strength), morphological characteristics (via SEM), and hydrolytic aging behavior were evaluated. Among the tested systems, PLA reinforced with seashells (PLA15S) and coffee grounds (PLA15C) demonstrated the most balanced mechanical performance, with PLA15S achieving a tensile strength increase of 72% compared to neat PLA. Notably, PLA15C exhibited the highest stability after 28 days of hydrothermal aging, retaining ~36% of its initial tensile strength, outperforming other systems. In contrast, walnut-shell-filled composites showed the most severe degradation, losing over 98% of their mechanical strength after aging. The results indicate that both the physicochemical nature and morphology of the biofiller play critical roles in determining mechanical reinforcement and degradation resistance. This research underlines the feasibility of valorizing agri-food residues into biodegradable, semi-structural PLA composites for potential use in sustainable packaging or non-load-bearing structural applications. Full article

Tidal seashell waste represents an abundant, underutilized marine resource that poses environmental disposal challenges but offers potential as a sustainable bio-filler in epoxy composites. This study investigates its incorporation into bio-based epoxy systems to reduce reliance on non-renewable materials and promote circular economy objectives. Processed seashell powder was blended into epoxy formulations, and response surface methodology was applied to optimize filler loading and resin composition. Comprehensive characterization included tensile strength, impact resistance, hardness, density, and thermal conductivity testing, along with microscopy analysis to evaluate filler dispersion and interfacial bonding. The optimized composites demonstrated improved hardness, density, and thermal stability while maintaining acceptable tensile and impact strength. Microscopy confirmed uniform filler distribution at optimal loadings but revealed agglomeration and void formation at higher contents, which can reduce interfacial bonding efficiency. These findings highlight the feasibility of valorizing marine waste as a reinforcing filler in sustainable composite production, supporting environmental goals and offering a scalable approach for the development of durable, lightweight materials suitable for structural, coating, and industrial applications. Full article

To mitigate CO₂ emissions from raw material decomposition and reduce the consumption of natural resources, this study investigated the use of mussel and oyster shell waste as secondary raw materials in earthenware production. Mineralogical, chemical and thermal analyses confirmed their suitability as sources of bio-calcite. Specimens incorporating various replacement levels (0–100%) showed no significant differences in key properties. Plates produced with mussel-derived bio-calcite in a pilot plant exhibited comparable properties to standard ceramics, demonstrating their industrial viability. CO₂ emissions were reduced by 14% and 10% in mussel and oyster shell-based ceramics, respectively, potentially saving up to 53 kgCO₂eq/t under the European Emissions Trading System, if the shells are classified as by-products. These findings demonstrated that bivalve shell waste can effectively replace mineral calcite in earthenware products, reducing CO₂ emissions and virgin raw material consumption, diverting waste from landfills and promoting sustainability in the ceramic industry. Full article

The valorization of mollusk shell waste offers a promising alternative to conventional binders in soil stabilization, contributing to circular economy strategies and improved solid waste management. This study aimed to evaluate the mechanical and microstructural behavior of clayey soil stabilized with Waste Seashell Lime (WSL), a binder produced by calcining crushed snail and mussel shells at different temperatures (700–900 °C) and durations (2–4 h). A recommended calcination condition (800 °C for 2 h) was selected based on thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX) results. WSL was incorporated at 3%, 7%, and 11% by dry soil weight and activated using NaOH at molarities ranging from 0.5 to 2.0 mol/L. A total of 122 specimens were prepared and tested for unconfined compressive strength (UCS) after 7 and 28 days. The highest UCS (4605 kPa) was recorded for the mix with 11% WSL and 1.0 mol/L NaOH at 28 days. At lower contents (3% and 7%), WSL-treated soils outperformed those stabilized with Type III Portland cement (Type III PC) under the same curing conditions. SEM-EDS analysis revealed the formation of cementitious phases, such as C–S–H and C–A–S–H, and factorial ANOVA confirmed the statistical significance of the WSL content, curing time, and alkali concentration. These results confirm the research hypothesis and demonstrate that alkali-activated WSL, derived from marine shell waste, can serve as a technically viable binder while supporting circular economy principles and waste reuse practices. Full article