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Abstract: Conventional wooden dowel connections in timber structures rely on tight press-fit installation, which requires high insertion forces and often loosens over time due to stress relaxation. This study investigates an alternative approach that exploits the moisture-activated set-recovery of thermo-hydro-mechanically (THM) densified hardwood dowels to enable slip-fit assembly followed by self-tightening in service. To this end, European beech and black poplar were densified radially and tangentially at different compression ratios. They were then evaluated for swelling kinetics, swelling pressure, bending performance, and moisture-activated expansion using in-situ X-ray CT in water at 20 °C and 100 °C. Results show that activation kinetics can be controlled by temperature. Expansion was rapid within minutes in hot water and slower but equivalent in magnitude at room temperature. Beech outperformed poplar, with radial densification at 35 % compression ratio producing a peak swelling pressure of 5.7 MPa and a modulus of rupture of 268 MPa after activation. Poplar generated higher free expansion but significantly lower pressure due to its lower stiffness. Radial densification was consistently more effective than tangential, enhancing both expansion magnitude and pressure generation. Capillary uptake triggered expansion along the dowel length (∼30 mm in 1 h) and produced an elliptical expansion profile. Importantly, mechanical strength was retained post-activation, which confirms structural suitability. These results demonstrate that THM-densified beech dowels can offer a robust self-tightening mechanism, combining low-force installation with durable pressure generation and stable mechanical performance. This provides a viable path toward adhesive-free, metal-free, high-tolerance timber connections.
Keywords: THM densification, dowel laminated timber, CT scanning
Published in RUP: 28.01.2026; Views: 192; Downloads: 0
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Abstract: Wood is a versatile material widely used in building construction, but its low thermal mass limits its ability to regulate indoor temperatures and mitigate thermal load peaks. Phase change materials are effective at storing thermal energy, but when impregnated into wood, they leak out, compromising performance and restricting their use in buildings. This study introduces a novel one-step impregnation process combined with in-situ polymerization using furfuryl alcohol and a capric-stearic acid phase change material mixture to create a sustainable material for thermal energy storage. Various formulations were tested on European beech (Fagus sylvatica L.) to evaluate effectiveness of the approach. The results confirm that this method successfully prevents phase change material leakage. Moreover, differential scanning calorimetry and nuclear magnetic resonance verified that phase change materials retain their thermal energy storage functionality, with no chemical cross-linking between the phase change materials and furfuryl alcohol. The treated wood showed up to 185 % higher thermal energy storage capacity, enhanced dimensional stability (anti-swelling efficiency up to 87 %), and 28 % higher compressive strength than untreated wood. It is a step towards sustainable, multifunctional, leakage-free, enhanced mechanical properties, improved dimensional stability wood for thermal energy storage for building applications, with potential for further optimisation and characterisation.
Keywords: bio-based materials, fatty acid, furfuryl alcohol, sustainable building materials, wood modification, phase change materials
Published in RUP: 09.01.2026; Views: 172; Downloads: 9
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Abstract: Timber-concrete composite (TCC) structures offer higher stiffness and loading capacity compared to pure timber structures with similar dimensions. A more rigid adhesive interface between concrete and timber offers advantages over conventional connections (e.g., mechanical fasteners and notches) by ensuring strain compatibility between the two materials. Fiber-based textiles, such as alkali-resistant (AR) glass fiber fabric, provide electrochemical corrosion resistance when used as reinforcement in concrete. An innovative composite floor system was introduced in this study, comprising cross-laminated timber (CLT) and reinforced concrete embedded with lightweight AR glass textile reinforcement, rigidly bonded together through epoxy adhesive bonding. A comprehensive investigation on the flexural behavior of this composite structure panel was conducted. Instrumentation, like digital image correlation (DIC) and optical fiber sensors, was employed to record strain distribution and development during four-point bending tests on those panels. A nonlinear numerical model was developed to predict the flexural behavior of the panels using continuum damage evolution for timber, concrete damage plasticity (CDP) model, and cohesive contact behavior between timber layers, considering the non-glue edge in the transverse layer. Experimental results showed that the failure predominantly occurred in the transverse layer of the CLT in the TCC panels. Employing glass fabric reinforcement within the CLT-constituted TCC led to an increase in loading bearing capacity. Numerical simulation indicated that textile reinforcement embedded within TCC's concrete counteracted localized concrete tensile failure, preserving structural integrity, delaying cohesive failure between planks in CLT, and consequently amplifying ultimate loading capacity of TCC structure.
Keywords: CLT, TCC, adhesive bonding
Published in RUP: 23.12.2025; Views: 242; Downloads: 2
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Abstract: This study investigates the performance of fly ash-based geopolymer recycled aggregate concrete (GRAC) as a sustainable alternative to Ordinary Portland Cement (OPC) concrete, focusing on its compressive strength and behavior under high-temperature exposure (150 °C, 300 °C, 600 °C, and 900 °C). The research emphasizes the use of 100 % recycled concrete aggregates as a replacement for natural aggregates, with samples cured at ambient conditions and at 60 °C in an oven. Key factors, including water content and curing conditions, were evaluated to determine their influence on compressive strength and thermal stability. Results indicate that water content is the primary factor governing compressive strength, while recycled aggregates contribute to a secondary but notable effect. GRAC maintained up to 65 % of its initial strength after exposure to 600 °C, though strength degradation and severe cracking occurred at 900 °C. Oven-cured samples showed fewer surface cracks but experienced slightly higher mass loss than room-cured counterparts. This study highlights the potential of GRAC as an environmentally friendly material capable of withstanding moderate thermal conditions, providing significant contributions to green construction practices and the reuse of construction and demolition waste.
Keywords: geopolymer, recycled aggregate concrete, elevated temperature
Published in RUP: 23.12.2025; Views: 195; Downloads: 2
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Abstract: This review offers an intensive exploration of the compatibility between flax fibre and cementitious materials, including the kinetics of alkaline degradation of flax fibre, and the interaction between fibre leaching/degradation and cement hydration. This paper also focuses on in-depth insights into the formation and ageing mechanisms of the interfacial transition zone between flax fibre and the cementitious matrix, and in turn how the ageing mechanisms affect the mechanical properties and long-term durability of flax fibre/textile reinforced cementitious composites. A systematic literature review reveals that flax fibre offers superior alkaline resistance compared to other lignocellulosic fibres due to its high crystalline cellulose and low lignin content. While the rough surface of flax fibre enhances bonding with the cementitious matrix, its hydrophilic nature can increase porosity at the interfacial transition zone and promote fibre mineralisation due to fibre swelling and shrinkage. Flax fibre reinforced cementitious composites show comparable flexural and compressive properties to those reinforced with other fibres, while flax textile excels in improving ductility over other textiles and steel reinforcements. Additionally, flax fibre degrades at higher temperatures than sisal and jute fibres. Despite growing interest in flax fibre/textile reinforcement for cementitious composites, key gaps remain in understanding the kinetic mineralisation process of flax fibre, the effects of the alkaline environment and hydration heat on its degradation, and the impact of its alkaline degradation products on cement hydration. Further research is needed to develop direct pull-out testing methods, explore the thermal/fire behaviour of composite phases encompassing the polymeric coating, and create a sustainability framework that considers ecological impacts, recyclability, and waste management for natural fibre reinforced cementitious composites.
Keywords: interfacial transition zone, mechanical properties, aging mechanisms
Published in RUP: 23.12.2025; Views: 234; Downloads: 2
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