Vol.6,No.4,2026-Table of Contents
- OPEN ACCESS ARTICLE
- Sustainable architectural top additions with light-frame timber structures also incorporating dissipative braces
- Sustainable Structures Vol.6,No.4,2026 DOI:10.54113/j.sust.2026.000119 Online published:2026-9-9
- Abstract A study on sustainable architectural top additions for reinforced concrete (RC) buildings based on the use of light-frame timber (LFT) structures is presented in this article. The objectives of the study are: a) to evaluate the possibilities offered by traditional LFT solutions; b) to propose a new LFT configuration that incorporates a small-sized dissipative bracing (DB) system, easily hidden behind the sheathing panels of the timber structure; c) to extend the installation of the DB system to a small number of perimeter spans of the underlying RC structure in order to achieve its seismic retrofit with no architectural intrusion and interruption in the use of the building. For the simulated application of these structural solutions, a representative real case study is selected, consisting of a two-storey RC residential building characterized by an eccentric position of the RC core surrounding the stairwell. This causes significant seismic torsional response effects in plan, making this case particularly challenging. A single-storey architectural top addition is designed for the building, covering 63% of the flat roof level. The results of the study show that: thanks to its intrinsic lightness, the traditional LFT structure produces a moderate increase in inter-storey drifts and stress states in the structural members of the underlying RC structure, as compared to as-built conditions; the incorporation of the DB system in only eight spans of the LFT structure in the longitudinal direction of the building, and four spans in the transversal direction, allows to meet the basic design objective of almost completely annulling the increase in seismic demand caused by the construction of the upper addition; the seismic retrofit of the RC structure is achieved by extending the installation of the DB system only to 8% of its transversal spans, situated on the side façade, and no longitudinal spans, without any architectural impact on the building.… More
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- Experimental investigation of the effect of activated bamboo biochar blended cement on concrete properties
- Sustainable Structures Vol.6,No.4,2026 DOI:10.54113/j.sust.2026.000118 Online published:2026-9-9
- Abstract This study examined the effect of incorporating activated bamboo biochar into cement on concrete properties. Bamboo biochar, a carbon-rich material produced through pyrolysis, was used to replace cement at 0%, 5%, 10%, and 15% by weight in M20 grade concrete mix. This study evaluated the carbon sequestration capacity, physical and mechanical properties of pure and blended cement, properties of fresh and hardened concrete, and economic viability. The results showed that increasing the biochar content significantly enhanced CO₂ sequestration, with a maximum uptake of 49.05% at 15% replacement. However, higher biochar content increased the standard consistency, setting times, and water absorption, while decreasing the compressive strength. The 5% biochar mix slightly outperformed the control in terms of compressive and split tensile strengths, but higher percentages reduced these properties. The impact strength, ultrasonic pulse velocity, and water penetration tests also decreased with increasing biochar content. Microstructural analysis revealed higher carbon content but decreased levels of other elements with increased biochar. Economic analysis showed higher costs for biochar concrete mixes because of the higher unit cost of the biochar. Despite the increased expenses, integrating biochar into concrete offers significant environmental benefits, presenting a transformative innovation for sustainable construction.… More
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- Eco-friendly geopolymer composites: leveraging parawood ash for sustainable construction materials
- Sustainable Structures Vol.6,No.4,2026 DOI:10.54113/j.sust.2026.000117 Online published:2026-9-9
- Abstract Biomass is gaining in popularity as an energy source. However, the combustion process generates a significant amount of ash, posing an environmental challenge. Previous studies have explored the incorporation of biomass ash into cement concrete to reduce its environmental impact; however, this has resulted in reduced strength performance. Biomass ash has been increasingly used as a component of geopolymer binder materials. This research examined how the treatment processes influence the physical and mechanical properties of geopolymer mortars that include parawood ash and fly ash. The parawood ash was mixed at 0%, 20%, 40%, and 60% by weight of the binder, and the specimens were subjected to heat curing at 80°C for 6, 12, and 24 h and cured at ambient temperature (30 ± 2°C) for 24 h. The compressive strength, bulk density, compressive strength loss after immersion in seawater, microstructure, chemical composition, and mineral composition of the test specimens were evaluated. The results demonstrated significant improvements in compressive strength. The geopolymer specimens with 20% parawood ash, cured at ambient temperature for 24 h, achieved the highest compressive strength of 32.31 MPa at 28 days. However, the specimens subjected to heat curing for 6-24 hours exhibited optimal compressive strengths within the first 24 h. Prolonged heat curing also effectively reduced the bulk density of the geopolymer. In addition to enhancing the compressive strength, the incorporation of parawood ash contributes to the reduction of waste materials.… More
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- Mechanical properties and durability of mortar with full fine aggregate replacement using combined fly ash and bottom ash
- Sustainable Structures Vol.6,No.4,2026 DOI:10.54113/j.sust.2026.000116 Online published:2026-9-9
- Abstract This study aimed to investigate mechanical properties and durability of mortar containing fly ash (FA) and bottom ash (BA) as a full replacement of fine aggregate. Different combinations of BA and FA were tested for mechanical properties and durability over 180 days. The results showed that mortar containing FA and BA required extra water to achieve similar workability as the control mortar. Furthermore, 90BA:10FA and 80BA:20FA mortars had higher compressive and split tensile strengths compared to the control at all curing ages due to the contribution of the pozzolanic reaction of FA. The presence of FA reduced porosity due to the pozzolanic reaction and micro-aggregate effect. This was particularly observed at the end of the curing, showing the production of high-quality mortar. Based on the results, combining of 80%BA and 20%FA offered a sustainable alternative to naturally sourced fine aggregate that produced mortar of comparable performance.… More
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- Experimental investigation on failure behavior of a novel high-tensile FRP-metal crimped thread connection
- Sustainable Structures Vol.6,No.4,2026 DOI:10.54113/j.sust.2026.000115 Online published:2026-9-9
- Abstract A novel fiber-reinforced polymer (FRP)-metal crimped thread connection (FMCTC) is developed for lightweight emergency truss bridge system constructed with pultruded FRP tubes. Experimental investigations were conducted to evaluate the feasibility, manufacturability, tensile behavior, and failure mechanisms of this new composite connection. The results reveal that the design successfully eliminates secondary processing and specialized tooling of parent FRP tubes; instead, composite threads are efficiently formed via passive crimping equipment. By integrating spiral-crimped thread geometry with preloaded high radial pressure, the specimens achieve 65% connection efficiency relative to base FRP strength. Two dominant failure modes are identified: (i) primary shear failure of the crimped FRP threads followed by interfacial slippage, and (ii) secondary failure patterns involving localized cross-sectional fractures coupled with longitudinal cracking in extended FRP tubes. Notably, despite distinct failure modes, all specimens exhibit minimal variation in ultimate loads. The substantial bearing strength, reaching up to 836.3 MPa, is governed by the shear resistance mechanism of the FRP threads. Owing to its manufacturing simplicity, enhanced connection efficiency, and exceptional load-bearing capacity, the newly developed FMCTC offers a viable technical solution for practical deployment in lightweight emergency truss bridge systems.… More
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