Vol.6,No.3,2026-Table of Contents
- OPEN ACCESS ARTICLE
- Innovative hybrid timber floor with simplified construction and calculation fully within the Eurocode 5 to promote sustainable timber-based flooring
- Sustainable Structures Vol.6,No.3,2026 DOI:10.54113/j.sust.2026.000113 Online published:2026-8-14
- Abstract Timber–concrete composite floors are currently used as sustainable flooring solutions. To broaden their application, improvements in construction efficiency are required. The hybrid system herein proposed combining timber, steel, and concrete members eases on-site assembly and can be partially prefabricated in factory. Timber beams and steel members, connected with interposed wooden planks through mechanical fasteners, create an oak-beamed ceiling supported by timber–steel composite beams. The steel element, with height equal to the insulating layer already required for energy and comfort purposes, plays a key role during concrete casting, allowing timber-steel composite beams to support fresh concrete and workmen loads with limited deflection. This composite action reduces the timber beam depth, thus lowering material use, and eliminates temporary supports, simplifying construction and reducing costs. These advantages promote wider adoption of timber floors, valued for both sustainability and aesthetics. After concrete hardening, a three-member hybrid floor is obtained. Neither numerical evaluations nor specific experimental tests are required because, even disregarding the steel contribution, the system’s performance, simply evaluated with the rules of the Annex B of Eurocode 5, generally accepted also for timber–concrete composites, matches that of conventional solutions with deeper timber beams. The proposed hybrid floor thus combines sustainability, prefabrication, construction efficiency, and compatibility with existing design standards.… More
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- OPEN ACCESS ARTICLE
- Bayesian optimization-enhanced machine learning axial load prediction across diverse CFST columns, strengths, geometries, and slenderness
- Sustainable Structures Vol.6,No.3,2026 DOI:10.54113/j.sust.2026.000112 Online published:2026-8-14
- Abstract Concrete-filled steel tubes (CFST) are recognized for their superior structural performance, offering enhanced strength, ductility, and construction efficiency. This enhanced performance is primarily due to the synergistic relationship between the steel casing and the concrete core; the steel imparts confinement to the concrete, thereby augmenting its compressive strength and ductility, while the concrete infill simultaneously restrains the steel tube against local buckling. This study addresses the critical need for accurate prediction of axial compression capacity in diverse CFST columns, spanning both circular and rectangular cross-sections, and encompassing short to slender configurations. A key focus was accommodating a wide range of material strengths, from conventional normal concrete and steel to contemporary ultra-high-performance concrete and high-strength steel. To achieve this, advanced machine learning (ML) algorithms specifically, ExtraTrees, XGBoost, and GradientBoosting, were employed. The hyperparameters of these models were optimized using Bayesian Optimization to maximize predictive efficacy. The developed models were rigorously validated through 10-fold cross-validation, demonstrating high accuracy, with coefficients of determination (R²) achieving up to 0.99 in predicting CFST column failure loads. Comprehensive error and sensitivity analyses were conducted to thoroughly assess their predictive capabilities and robustness. Furthermore, SHapley Additive exPlanations (SHAP) analysis was utilized to elucidate model decision-making processes and identify the most influential input parameters, enhancing interpretability and confidence. This research significantly advances the efficient, reliable, and data-informed design of CFST structures, expanding their applicability and fostering greater industry acceptance, particularly for innovative designs utilizing high-performance materials.… More
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- OPEN ACCESS ARTICLE
- FRP reinforced recycled aggregate concrete columns under static loading: a comprehensive review with machine learning perspectives
- Sustainable Structures Vol.6,No.3,2026 DOI:10.54113/j.sust.2026.000111 Online published:2026-8-14
- Abstract This review paper investigates the behaviour of fibre-reinforced polymer (FRP)-reinforced recycled aggregate concrete (RAC) columns under static loading conditions. The adoption of RAC, which uses recycled materials, is essential for sustainable construction, but its reduced mechanical properties pose challenges. To enhance RAC structural performance, FRP composites are applied to improve compressive strength, ductility, and energy dissipation capacity. FRP confinement mechanisms, including external wrapping and hoop reinforcement, provide lateral support, effectively increasing the axial load capacity of RAC columns and delaying failure mechanisms such as concrete crushing and FRP debonding. This paper examines over 100 studies, focusing on key parameters such as FRP material type (carbon, glass, aramid), the confinement effect of FRP, and the recycled aggregate replacement ratio. The review finds that FRP reinforcement significantly enhances RAC columns' compressive strength and ductility, with axial load capacity improving by up to 88.7% and energy dissipation increasing by 24.5%. However, the interaction between FRP and RAC remains complex, with increased recycled aggregate replacement ratios resulting in a decrease in compressive strength by approximately 19% at 100% replacement. Despite the positive outcomes, challenges such as long-term durability, environmental impact, and cost-effectiveness remain. The research identifies gaps, including the need for more studies on long-term performance, life-cycle assessments (LCA), and the development of predictive models for FRP-RAC columns. Key conclusions highlight that FRP reinforcement can boost column strength and ductility, but further investigation into environmental impacts and long-term behaviour is necessary. The review emphasizes future research directions to optimize FRP-RAC column design and sustainability.… More
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- Innovative use of rice husk ash in sustainable cement mortar: insights from machine learning on oxide influence
- Sustainable Structures Vol.6,No.3,2026 DOI:10.54113/j.sust.2026.000110 Online published:2026-8-14
- Abstract This study explores the use of rice husk ash (RHA) as a supplementary material in cement mortar, focusing on its impact on compressive strength through machine learning predictive modelling. The methodology involved a systematic literature review to compile a comprehensive dataset of 692 records from 20 published sources. A range of machine learning techniques, comprising Linear Regression, Artificial Neural Networks, Random Forest Regression, and Extreme Gradient Boosting, were utilized to assessment compressive strength based on important variables such as the ratios of aggregate-to-binder, RHA-to-binder, water-to-binder, along with the curing time and chemical composition. Results designate that RHA significantly contributes to the pozzolanic activity of cement mortar, with optimal RHA-to-binder ratios enhancing compressive strength without compromising workability. The machine learning models exhibited high predictive precision, with R² values more than 0.95 and low RMSE values across the tested datasets. Sensitivity analysis has shown that the aggregate-to-binder ratio, SiO2 content and curing period were the important parameters affecting compressive strength, emphasizing the significance of precise formulation. The study recommends further research to validate the predictive models through experimental studies, broaden the dataset for enhanced generalizability, and explore additional chemical compositions of RHA.… More
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- Eco-friendly protective coating made from geopolymer mortars for conventional concrete in a marine environment
- Sustainable Structures Vol.6,No.3,2026 DOI:10.54113/j.sust.2026.000109 Online published:2026-8-14
- Abstract Geopolymer mortar offers an eco-friendly way to protect concrete in harsh environments. Affordable materials such as fly ash (FA) and rice husk ash (RHA) improve sustainability, with RHA providing silica. The long-term effects of geopolymer and Portland cement in marine environments, especially under severe sulfate attack, remain largely unexplored. Understanding interface mineral formations is key to evaluating concrete's resistance to chemical infiltration. This study evaluated geopolymer mortar containing 0–10% RHA, replacing FA, as a protective layer for Portland concrete. Samples were exposed to chloride- and sulfate-rich seawater for 5 months to evaluate mechanical strength, porosity, sulfate resistance, chloride penetration, and interface behavior. A 5% RHA replacement (Si/Al = 3.26) optimized performance, enhancing chemical bonding at the interface through C-A-S-H formation. The geopolymer layer significantly improved sulfate resistance, outperforming Portland mortar with 20% FA (FPC). Marine exposure accelerated geopolymerization, increasing density and compressive strength while reducing chloride ingress. The protective N-A-S-H gel, stabilized by Fe, Al, and Mg, remained resistant to sulfate and chloride ions. Additionally, dissolved silica from RHA mitigated degradation and reduced CO₂ emissions by 62.1%. The study showed that geopolymer mortar is promising for jacketing, repairing, or patching concrete structures in marine environments.… More
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