Search Results (208)

Artificial reefs are an important tool for marine ecological restoration and fishery resource proliferation, and are widely used around the world. Among them, Japan, the United States, China, South Korea, Australia, and the Mediterranean coastal countries have particularly invested in scientific research and practice in this field, and the reefs’ material selection, structural performance, and ecological benefits have attracted much attention. The purpose of this paper is to summarize the preparation methods, characterization methods (such as microstructure analysis and mechanical tests) and mechanical properties (such as compressive strength and durability) of new concrete materials (steel slag-blast furnace slag concrete, oyster shell concrete, sulfoaluminate cement concrete, recycled brick concrete, silica fume concrete, and banana peel filler concrete) that artificial reefs and ceramic artificial reefs developed in recent years, and to explore the resource utilization potential of different waste materials. At the same time, the biostatistical methods (such as species abundance and community diversity) of wood, shipwreck, steel, rock, waste tire, and ordinary concrete artificial reefs and their effects on the marine environment were compared and analyzed. In addition, the potential impact of artificial reef deployment on local fishermen’s income was also assessed. It is found that the use of steel slag, blast furnace slag, sulfoaluminate cement, and silica fume instead of traditional Portland cement can better improve the mechanical properties of concrete artificial reefs (compressive strength can be increased by up to 20%) and reduce the surface pH to neutral, which is more conducive to the adhesion and growth of marine organisms. The compressive strength of oyster shell concrete and banana peel filler concrete artificial reef is not as good as that of traditional Portland cement concrete artificial reef, but it still avoids the waste of a large amount of solid waste resources, provides necessary nutritional support for aquatic organisms, and also improves its chemical erosion resistance. The deployment of artificial reefs of timber, wrecks, steel, rock, waste tires, and ordinary concrete has significantly increased the species richness and biomass in the adjacent waters and effectively promoted the development of fisheries. Cases show that artificial reefs can significantly increase fishermen’s income (such as an increase of about EUR 13 in the value of a unit effort in a certain area), but the long-term benefits depend on effective supervision and community co-management mechanisms. This paper provides a scientific basis for the research and development of artificial reef materials and the optimization of ecological benefits, and promotes the sustainable development of marine ecological restoration technology and fishery economy. 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

After the Spanish Civil War, the shortage of building materials in the country and the restrictions imposed by the Dirección General de Arquitectura limited the use of steel in construction, encouraging solutions that reduced the consumption of this material. In this context, the thin-tile vault gained new relevance due to its low cost, speed of execution and good structural and fire performance. Among the architects who revisited this system, Ignasi Bosch Reitg (1910–1985) developed an innovative procedure for the construction of continuous ceilings, based on double-curved vaults with a single layer of brick. His cousin, Josep Maria Bosch Aymerich (1917–2015), an industrial engineer and architect trained in the United States, brought a business vision to the table when he discovered the potential of this system. This paper proposes an in-depth study of the patents requested on this system by the two architects, questioning the reasons for their success or failure in different countries, both in terms of dissemination and exploitation, in regard to the historical context in which it was developed. The analysis, based on original documents from the Bosch Aymerich Archive, uncovers the tensions that the reinterpretation and global projection of a traditional technique can generate. Full article

The disposal of industrial waste poses a significant environmental challenge, often leading to pollution and degradation of surrounding and terrestrial ecosystems. This study investigates the sustainable valorization of such wastes through the development of one-part geopolymer mortars. Solid sodium silicate was employed as a dry alkali activator for binary blends comprising ground granulated blast-furnace slag (GGBS), clay brick powder (CBP), steel slag (SS), and fly ash (FA), with all mixtures cured under ambient conditions. The mortars were evaluated in terms of fresh properties (flow and setting time) and hardened characteristics, including compressive strength, density, water absorption, and porosity. Durability performance was assessed through mass loss, visual degradation, and compressive strength retention following exposure to acidic (H₂SO₄, HCl) and sulfate environments. Microstructural characterization using XRD, SEM, and FTIR provided insight into the mechanisms of gel formation and degradation in aggressive media. The results revealed that incorporating 5% FA into GGBS-based mortars enhanced 28-day compressive strength by 21.7% compared with the control mix. The inclusion of industrial by-products promoted the formation of C–S–H and C–(A)–S–H gels, contributing to a denser and more refined microstructure. Overall, the findings demonstrate that one-part geopolymer mortars offer a promising, eco-efficient, and durable alternative to traditional cementitious systems, while also addressing safety and handling concerns associated with liquid alkaline activators used in conventional two-part geopolymer formulations. Full article

The re-valorisation of oyster-shell waste offers a sustainable pathway for producing eco-efficient construction materials. This study investigates the physical, mechanical, and durability performance of natural hydraulic lime (NHL) mortars incorporating oyster shells (OSs), applied to solid bricks representative of historical masonry. Two formulations were developed: one with 24% replacement of NHL by oyster-shell powder (OSP, <150 µm) and another with 30% substitution of sand by oyster-shell aggregate (OSA, 0–4 mm), both compared with a control mortar. Mortars were tested in standard molds and directly applied to bricks, including under accelerated aging conditions (temperature and humidity cycles). Results revealed that shell-incorporated mortars applied to bricks exhibited higher bulk density and compressive strength, and lower porosity, capillary water absorption, and water vapor permeability, compared with mold-cast samples. The performance for the shell-based mortars highlights the substrate–mortar interaction, consistent with the behavior of traditional lime-based systems, and the microscope characterization (poro-Hg and X-ray tomography). Shell-incorporated mortars retained stable properties after aging, with variations below 10% compared to unaged mortars. These findings demonstrate the feasibility of oyster shells as partial replacements for lime and sand, confirming its potential as an eco-efficient strategy for sustainable mortars in conserving and rehabilitating historic masonry buildings. Full article

In the context of advancing sustainable local building materials, this study evaluates the mechanical impact of polypropylene (PP) fiber reinforcement on adobe bricks, specifically addressing the novel variable of fiber addition timing relative to the traditional 45-day biological fermentation process. Two experimental scenarios were investigated: fiber addition before fermentation and fiber addition after fermentation. In the pre-fermentation scenario, the unreinforced control specimen achieved the highest mean compressive strength (1.92 MPa), followed by reduced values of 1.66 MPa (0.25%), 1.60 MPa (0.50%), and 1.55 MPa (1.00%). In the post-fermentation scenario, the control recorded 1.81 MPa, while the PP-reinforced mixtures reached 1.73 MPa (0.25%), 1.65 MPa (0.50%), and 1.77 MPa (1.00%). Across both stages, PP fibers consistently decreased in strength due to weak bonding at the fiber–soil interface, as their hydrophobic nature disrupts the fermentation-derived biopolymer network formed by straw decomposition. Overall, this study highlights the limitations of synthetic fiber reinforcement within biologically stabilized adobe and contributes to the ongoing development of sustainable earthen construction systems. Full article

Inner courtyards have been traditionally used as passive strategy in vernacular buildings in desert climates. This paper presents a study conducted to investigate indoor and outdoor thermal comfort of two vernacular buildings in the hot arid climate of Upper Egypt and proposes an improved solution for courtyards to achieve sustainable development of current vernacular houses and apply the same in the arid climate zone of Egypt. The thermal comfort of vernacular building spaces was evaluated based on using field measurements during the hot season and improvement for courtyards based on ENVI-met V5.6.1 simulation model using three scenarios. Two vernacular buildings (Hassan Fathy and Nubian house) were selected to represent the traditional buildings south of Egypt. The study found that using adobe bricks with high thermal mass in vernacular buildings maintained lower indoor temperature with a range of 2.7 °C to 6.7 °C compared to outdoor temperature; this is considered effective thermal insulation. Meanwhile under extreme hot conditions, courtyard temperature inside the vernacular house was 0.3 K higher than the outdoor. This is not sufficient to maintain indoor thermal comfort without integrating passive solutions inside courtyards. In addition, applying the hybrid solution with big dense trees in the courtyards achieved a significant reduction in PET ranging from 4.2 °C and 5.7 °C; shading the widest area of courtyards and allowing for family activities. The study provided techniques and methodology for the middle courtyard of vernacular buildings, demonstrating how improvement achieves thermal comfort and sustainable development required in the 21st century in Upper Egypt, and can be applied to other vernacular houses in different desert cities in southern Egypt. Full article

Traditional stone cave dwellings in northern Shanxi exhibit distinct differences from conventional cave dwellings in terms of form and material, characterized by their freestanding stone-built structures that possess unique value. In the context of rapid urbanization, these dwellings encounter issues related to decreasing quantities and a lack of comprehensive systematic research. This research utilizes a mixed objective–subjective methodology to assess the indoor environment of the stone cave dwellings in Dongwa Village, Shuozhou City. Thermal comfort is evaluated using the PMV-PPD and TSV models, whereas air quality is assessed through gray correlation analysis. Results indicate: (1) The thermal inertia of stone cave dwellings’ envelopes significantly surpasses that of brick structures. However, their exterior wall and roof thermal conductance coefficients exceed national standard limits, respectively, by 4 times and 1.7 times; (2) The PMV thermal neutral temperature (21.32 °C) was notably higher than the TSV thermal neutral temperature (10.96 °C), suggesting that residents have developed cold adaptation. The thermal preference temperature (12.75 °C) exceeded the TSV value, reflecting strong resident demand for improvements; (3) Winter pollutant exceedance rates were markedly higher than those in summer, with air quality classified as experiencing “heavy pollution” levels. Residents reported a high level of subjective satisfaction, suggesting the presence of a cognitive bias. This study aims to reveal environmental issues in traditional local stone cave dwellings under modern residential demands, providing references for sustainable improvements in rural building environments. Full article

Interlocking Compressed Earth Blocks (ICEBs) offer a sustainable alternative to conventional fired-clay bricks but remain hindered by inconsistent geometric designs and limited standardization. This study develops a stakeholder-weighted Analytic Hierarchy Process (AHP) framework to evaluate and select the most suitable ICEB geometry for sustainable and seismic-ready construction in developing regions. Five evaluation criteria—size, weight, interlocking effectiveness, reinforcement/grout provision, and handling ergonomics—were prioritized based on expert input from masons, engineers, architects, and researchers. The synthesized results ranked the HiLo-Tec-type geometry highest, followed by Thai-Rhino, Auram, and Hydraform designs. Unit weight (0.289) and reinforcement capacity (0.261) emerged as dominant decision factors. Sensitivity analysis confirmed the robustness of rankings under varying weight perturbations. The AHP framework identifies the top-ranked geometry, whose structural performance was examined experimentally through a full-scale cyclic test on a grouted double-wythe ICEB wall, revealing enhanced ductility and residual strength compared with traditional brick masonry. The proposed framework demonstrates that selected ICEB geometry can balance ergonomic and structural performance while meeting seismic resilience demands. Beyond geometry selection, the model provides a replicable decision-support tool adaptable for regional material innovations in sustainable construction. Full article

Earthen heritage in desert oases reflects local identity, craftsmanship and traditional knowledge but is facing increasing threat of disappearance from material vulnerabilities, social abandonment and unsuitable interventions. This study develops and validates a novel decision-making tool to guide stakeholders in selecting the most suitable building technology for the adaptive reuse of earthen heritage complexes to ensure their long-term sustainability while maintaining their cultural and social values. The proposed methodology combines the Integrated Value Model for Sustainability Assessment (MIVES) and Delphi technique to evaluate the cultural, economic, environmental and social aspects. Quantitative and qualitative indicators were defined through literature review and weighted by experts in two rounds of Delphi to obtain comparable sustainability index for each building technology. The evaluation of economic and environmental aspects was based on literature data, while cultural and social aspects were assessed through a third round of Delphi with local participants. The tool was applied to the Adrere Amellal Ecolodge in Siwa Oasis, Egypt, comparing three building technologies: Karshif traditional earthen technique, commonly used red bricks and innovative 3D-printed saltblocks. Karshif achieved the highest sustainability index (0.77) due to its cultural values, social acceptance and environmental performance. The findings demonstrate the potential of traditional earthen techniques to ensure sustainable adaptive reuse, providing a replicable method for sustainable adaptive reuse of earthen heritage in desert oases in Egypt and worldwide. Full article

The failure behaviour of historic unreinforced masonry (URM) structures is strongly influenced by the properties of bricks and mortar. Over time, degradation processes compromise these materials, with significant effect on structural response and safety. Nevertheless, deterioration effects on the nonlinear behaviour of masonry have been only marginally investigated. This study investigates the mechanical behaviour and failure mechanisms of historic brick masonry with weak and irregular mortar joints, representative of Mediterranean traditional constructions. An extensive experimental programme was conducted on mortars, historic clay bricks, prisms, wallets, and triplet specimens, complemented by in-situ flat jack tests. Results confirm the critical role of mortar quality and joint irregularities in reducing compressive and shear strength and in influencing deformation capacity of historic masonry. The experimental findings served as a basis for the calibration of a Finite Element Model (FEM), subsequently employed to gain deeper insight into the governing failure mechanisms in a real study case. A critical discussion of compression and shear failure criteria is presented, focusing on historic masonry. Experimental and analytical comparisons show major discrepancies in classical criteria, especially with degraded mortars. The study shows that in historic masonry with weak joints, failure is often governed by compression rather than shear. Full article

The study investigates the potential of using Vietnam fly ash (FA) as a substitute for traditional Portland cement to reduce both the volume of landfilled waste and the carbon footprint of concrete mixtures, while maintaining adequate mechanical performance of the produced elements. Additionally, the incorporation of construction and demolition waste, recycled brick aggregate (BR), as a partial aggregate substitute was investigated to enhance the sustainability and resource efficiency of composite formulations. Five mixes, including a reference, were produced by casting and three-dimensional concrete printing (3DCP). Printability (flow table), water absorption (gravimetry and infrared thermography), and flexural/compressive behavior were assessed; printed specimens were tested parallel and perpendicular to the layer plane. Recycled additions reduced flow by 15–22%, yet all mixes remained printable. Printed specimens showed higher capillary uptake than cast ones. In flexure, modified mixtures composition exhibited 50% lower peak stress than the reference. Cast elements outperformed printed ones: the printed reference was 33% weaker than its cast counterpart, and other mixes were 10–15% lower. In compression, printed specimens loaded perpendicular to layers reached 6–7 MPa (35% below cast), whereas parallel loading yielded up to 3.5 MPa with larger scatter. The findings confirm the feasibility of utilizing secondary raw materials in 3DCP formulations to support resource efficiency and carbon footprint reduction in the construction industry. Full article

The study highlights the morphological features of mud-brick architecture in Syria, based on a descriptive and analytical approach. The research begins with a theoretical introduction about the studied area and mud-brick architecture, then their urban characteristics, including (design, function and classification). After that, the elements of the mud building in Rif Dimashq, such as foundations, walls, ceilings and cladding are studied. The discussion includes the advantages and disadvantages of mud-brick architecture, its future in Syria through presenting experiences and conducting a questionnaire for two different samples of residents and engineers about the research topic. Finally, the results document Syrian mud-brick architecture and identify its basic morphological elements, providing sustainable design ideas based on traditional construction techniques, with guidelines for developing sustainable future housing that is both heritage oriented and modern. Full article

Wearable, rectifiable aerosol photometers (WRAPs), instruments with combined nephelometer and on-board filter-based sampling capabilities, generally show strong correlations with reference instruments across a range of ambient and household PM_2.5 concentrations. However, limited data exist on their performance when challenged by mixed aerosol exposures, such as those found in dusty occupational environments. Understanding how these instruments perform across a spectrum of environments is critical, as they are increasingly used in human health studies, including those in which concurrent PM_2.5 and coarse dust exposures occur simultaneously. The authors collected co-located, ~24 h. breathing zone gravimetric and nephelometer PM_2.5 measures using the MicroPEM v3.2A (RTI International) and the UPAS v2.1 PLUS (Access Sensor Technologies). Samples were collected from adult brick workers (n = 93) in Nepal during work and non-work activities. Median gravimetric/arithmetic mean (AM) PM_2.5 concentrations for the MicroPEM and UPAS were 207.06 (interquartile range [IQR]: 216.24) and 737.74 (IQR: 1399.98) µg/m³, respectively (p < 0.0001), with a concordance correlation coefficient (CCC) of 0.26. The median stabilized inverse probability-weighted nephelometer PM_2.5 concentrations, after gravimetric correction, for the MicroPEM and UPAS were 169.16 (IQR: 204.98) and 594.08 (IQR: 1001.00) µg/m³, respectively (p-value < 0.0001), with a CCC of 0.31. Digital microscope photos and electron micrographs of filters confirmed large particle breakthrough for both instruments. A possible explanation is that the miniaturized pre-separators were overwhelmed by high dust exposures. This study was unique in that it evaluated personal PM_2.5 monitors in a high dust occupational environment using both gravimetric and nephelometer-based measures. Our findings suggest that WRAPs may substantially overestimate personal PM_2.5 exposures in environments with concurrently high PM_2.5 and coarse dust levels, likely due to large particle breakthrough. This overestimation may obscure associations between exposures and health outcomes. For personal PM_2.5 monitoring in dusty environments, the authors recommend traditional pump and cyclone or impaction-based sampling methods in the interim while miniaturized pre-separators for WRAPs are designed and validated for use in high dust environments. Full article

In response to escalating environmental concerns, the construction industry is under growing pressure to adopt sustainable practices. As a major consumer of natural resources and a significant emitter of greenhouse gases, it paradoxically holds the potential to become a leader in green transformation. This study investigates the development of innovative, fire-resistant, and alkali-activated hybrid binder foams incorporating recycled materials: fly ash, coal slag, and ground brick waste, as sustainable alternatives to traditional building materials. The fire resistance performance at a technical scale and the thermal behavior of fiber-reinforced, alkali-activated hybrid binder foams synthesized from recycled aluminosilicate precursors were determined. The properties of unreinforced composite were compared with the composites reinforced with merino wool, basalt fibers, polypropylene fibers, and coconut fiber. Small-scale fire-resistance tests revealed that merino wool-reinforced composites exhibited the best thermal insulation performance, maintaining structural integrity, that is, retaining shape and continuity without delamination or collapse for 83 min under fire exposure. Analyses combining chemical characterization (X-ray fluorescence) with microstructural methods (computed tomography and colorimetry) confirmed that fire performance is strongly influenced not only by fiber type but also by pore distribution, phase composition, and oxide migration under thermal loading. These findings demonstrate the potential of fiber-reinforced foamed, alkali-activated hybrid binder as eco-efficient, printable materials for fire-safe and thermally demanding construction applications. Full article