Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2026
Abstract
This study investigates the moisture-induced recovery of temporary property changes in thermo-mechanically densified (TMD) birch and aspen wood, compared to thermally modified (TM) wood. Both treatments were prepared under identical thermal conditions, differing only by compression in TMD. Dimensional stability, water vapour sorption, and Brinell hardness were assessed before and after repeated wetting and drying cycles to evaluate the effect of stress storage in the polymer matrix and its recovery during moisture exposure. The results indicate that both TMD and TM treatments induce a temporary reduction in moisture uptake, consistent with the formation of an annealed polymer structure. Water saturation and subsequent drying restored higher moisture content and reduced Brinell hardness in TMD wood, highlighting a moisture-driven recovery of the annealed polymer conformation. Notably, the decrease in hardness could not be attributed solely to the reduction in bulk density, indicating additional effects of polymer plasticisation. The presence of compression stresses during TMD appeared to enhance stress storage, thereby influencing the recovery of moisture-induced properties. Initial wood moisture content before TMD had little effect on the temporary reduction in moisture content, suggesting that annealing also occurs in dry states. These findings emphasise the need to account for moisture cycling in TMD wood’s service life. Future work should focus on the interplay between compression stresses and the annealing effect to reduce the temporary nature of the property improvements by TMD.
Abstract
Wood has many attractive material qualities, but it is susceptible to biological degradation by wood-decaying fungi. Moisture is one of the critical requirements for wood decay, but much remains unknown about moisture dynamics in decaying wood. To fill this knowledge gap, this study investigated moisture in Scots pine sapwood during decay caused by the brown rot fungus Coniophora puteana. Samples were exposed to decay in two time-series experiments; mass loss and moisture content were recorded over the course of decay, and the bound and free water populations in the samples were analysed using low-field nuclear magnetic resonance (LFNMR) relaxometry in both the decaying state and at full water saturation. Selected samples were also used for water vapour sorption measurements. The time-series decay tests showed that moisture content initially increased due to fungal activity but decreased over time when corrected for mass loss, contrary to the general belief that moisture content increases with decay. LFNMR revealed that bound water content increased on a decayed-mass basis in the decaying state and at saturation, but no increase was seen after correction for mass loss. Free water content followed gravimetric moisture content in the decaying state, but the saturated state measurements revealed an initial increase and subsequent decrease with mass loss. Degradation caused changes in hygroscopicity, but our data show that overall moisture content is regulated by fungal activity rather than by material properties. These findings highlight the complexity of water interactions during fungal degradation, offering valuable new insights into wood degradation mechanisms.
Authors
Kristina Bringedal Gedde Georgios Triantafyllidis Alessio Miatto Lone Ross Lizhen Huang Daniel Beat MuellerAbstract
Abstract The building sector accounts for a significant share of global material stocks and embodied greenhouse gas emissions. Material intensity (MI), defined as construction materials per unit floor area, is a key metric for understanding resource use and environmental performance. Existing approaches estimate MI for specific building types and cohorts but rarely explore additional factors that influence the structural element requirements. This study refines traditional methods by incorporating building geometry, number of floors, geographical context, construction methods, and regulatory changes, using Norwegian residential buildings as a case study. We focus on stud use in exterior walls to understand how their MI (kg/m 2 ) varies across buildings. Our correlation analysis reveals that construction year (ρ = 0.69) and energy efficiency standards (ρ = 0.51) are associated with higher MI of studs while building length shows a notable negative correlation (ρ = –0.38). Timber stud MI increases with footprint complexity and number of floors but decreases as building length and floor area grow. Snow load further contributes to increased stud MI. Studs' MI also varies across periods, reflecting changes in regulations and construction practices. These findings enhance our understanding of material use drivers in timber structures and provide a foundation for developing more nuanced building stock models to improve resource efficiency assessments and support targeted climate mitigation strategies.
Abstract
This paper presents a comprehensive study on lightweight cement-bonded composites containing pulp sludge (PS). The objective of the study was to evaluate how the incorporation of perlite (a lightweight volcanic glass aggregate) and lime mud (a pulp mill residue) influences composites’ properties including mechanical strength, insulation and fire resistance. Up to 50% of the cement binder was replaced with PS (by mass), and small fractions of cement (5–15%) were replaced with perlite or lime mud. A suite of analytical techniques, material characterization and mechanical tests with digital image correlation (DIC) for strain analysis were employed. X-ray analysis showed that the aggregates influenced the composite properties to a considerable extent due to their particle sizes and ability to form hydrated gels with cement. Adding 5% of perlite or lime mud yields optimal strength without compromising weight reduction whereas higher aggregate content (15%) led to reduced strength. The DIC system provided insights into strain distribution during loading, confirming enhanced toughness from the fibrous PS. The composites were significantly lighter (732–749 kg/m3) and showed about 30% lower thermal conductivity (0.17 W/mK) than pure cement composites (0.25 W/mK). The normal incidence sound absorption of the composites was about 0.3 at mid-high frequencies due to their compact structure. The composites demonstrated potential for use as sustainable, lightweight construction materials with good acoustic and thermal insulation, as well as acceptable load-bearing capacity for non-structural applications based on EN 634-1/-2 requirements for cement-bonded particleboards.
Authors
Dafni Foti Stephen Amiandamhen Eleni Voulgaridou Elias Voulgaridis Costas Passialis Stergios AdamopoulosAbstract
Abstract This study investigated the incorporation of various waste materials including wastepaper, Tetra Pak, wood chips and scrap tire fluff into flue gas desulfurization (FGD) gypsum and cement mortar matrices to produce sustainable composite materials. Four distinct composite types based on the waste materials were developed and evaluated for selected properties including thermal and acoustic insulation. The proportion of the waste materials was varied between 10 and 40 vol% of the base matrix. The compressive strength of the filled gypsum composites was in the range of 4.17–10.39 N/mm² while the pure gypsum was 11.38 N/mm². The addition of the wastes in gypsum composites reduced compressive strength by about 10% for the best recipe and as large as 60% for the worst combination. However, the measured strength still exceeds the strength of typical gypsum wallboard with a compressive strength of about 3–4 N/mm² for whole-board crushing tests and it is much lower for point loads. The normal-incidence sound absorption coefficient indicated that the waste-filled samples absorbed around 80% of the incident sound energy between 2000 and 3000 Hz, comparable to some commercial acoustic foams. The results highlight the potential of utilising these waste-based composites in environmentally friendly construction applications. Depending on the waste type and matrix used, the results revealed trade-offs between multi-functional performance and sustainability benefits.
2025
Authors
Martin Nopens Imke Greving Silja Flenner Linnea Hesse Jan Lüdtke Michael Altgen Gerald Koch Johannes Beruda Sabrina Heldner Hannes Köhm Sergej Kaschuro Andrea Olbrich Jakob Benedikt Mietner Fabian Scheckenbach Jördis Sieburg-Rockel Andreas KrauseAbstract
Deep understanding of the structural composition and growth of biological specimens is becoming increasingly important for the development of bio-based and sustainable material systems. Full-field nano-computed tomography is particularly suitable for this purpose as it allows for non-destructive 3D imaging at high spatial resolution. However, most biological samples are functionalized by water and respond sensitively to any changes in climate conditions, specifically relative humidity, by adjusting their material moisture content. To date, only a limited number of tomography instruments offer an in situ climate control option to users. These, however, are limited either by the range of relative humidity states, the long times required to change the climate state, or obstruction or attenuation of the beam. Here, the first fully automatized climate cell for in situ full-field nanotomography is presented. It has been designed, built and integrated at the nanotomography station at the P05 imaging beamline, operated by Hereon at the DESY storage ring PETRA III, Germany. The highly flexible and windowless design allows the humidity dependent swelling and shrinking of lignified plant cell walls to be studied in situ, using phase contrast nanotomography. The concept of this climate chamber can easily be integrated into other setups. It operates in the relative humidity range of 0–90% and can be controlled in a temperature range of 10–50°C. Climate conditions can be adjusted at any time, remotely from the control hutch by using a humidity generator. Results show that the developed setup maintains a stable climate during the entire duration of a tomographic scan at different humidities and does not obstruct the sample or hinder the imaging conditions. During the tomographic investigation the sample remains stable in the flow of the air stream and shows typical cell wall swelling and shrinking behaviour depending on the equilibrium moisture content. This new climate cell is now available to all users of the P05 nanotomography instrument for conditioning samples, serving a wide range of scientific applications.
Authors
Samuel L. Zelinka Samuel V. Glass Natalia Farkas Emil E. Thybring Michael Altgen Lauri Rautkari Simon Curling Jinzhen Cao Yujiao Wang Tina Künniger Gustav Nyström Christopher Hubert Dreimol Ingo Burgert Mark G. Roper Darren P. Broom Matthew Schwarzkopf Arief Yudhanto Mohammad Subah Gilles Lubineau Maria Fredriksson Wiesław Olek Jerzy Majka Nanna Bjerregaard Pedersen Daniel J. Burnett Armando R. Garcia Frieder Dreisbach Louis Waguespack Jennifer Schott Luis G. Esteban Alberto García‑Iruela Thibaut Colinart Romain Rémond Brahim Mazian Patrick Perré Lukas EmmerichAbstract
Many studies that use an automated sorption balance to determine a water vapor sorption isotherm for wood collect data until the moisture content change is less than or equal to 0.002% min −1 (20 µg g −1 min −1 ). This stop criterion has been claimed to give errors in equilibrium moisture content (EMC) predictions of less than 0.001 g g −1 but over the past 10 years, studies have shown that the actual errors can be greater than 0.01 g g −1 because the measurements are stopped well before equilibrium is reached. Despite the large errors associated with this stop criterion, it remains popular due to the speed at which isotherms can be measured. This paper utilizes data from a worldwide interlaboratory study on automated sorption balances to develop a correction method for estimating EMC of western larch ( Larix occidentalis Nutt.) from the moisture content corresponding to the 20 µg g −1 min −1 criterion. The study uses data from 72 relative humidity absorption steps with hold times of 7–10 days from 21 different laboratories and eight different instrument models. EMC is defined based on the inherent mass stability of automated sorption balances determined in the first part of this interlaboratory study. On average the sorption process is less than 80% complete when the 20 µg g −1 min −1 criterion is reached, resulting in a mean absolute error (MAE) of 0.006 g g −1 . The correction equation for estimating EMC reduces the MAE to 0.001 g g −1 . The analysis presented in this paper, along with the correction equation, can be considered for certain use cases to reduce systematic errors and shorten measurement times.
Authors
Erik Larnøy Andreas Treu Manon Diraison Mathias Smith Anaël Audouin Peer Thorben Lewandowski Johan BiørnstadAbstract
No abstract has been registered
Authors
Gerhard Grüll Gry Alfredsen Geir Wæhler Gustavsen Boris Forsthuber Jonas Niklewski Philip Bester van Niekerk Lone Ross Christian BrischkeAbstract
A survey including 3112 responses from individual end users of wood cladding, from Norway, Sweden and Germany, was conducted with questions related to their experience and preferences regarding cladding with and without coatings. Based on these results and established scientific understanding of Service Life Prediction (SLP) of wood cladding, two decision trees were provided to guide end users in selecting a suitable material to meet their expectations when planning a new cladding. This approach makes the users reflect on maintenance requirements and aesthetic changes rather than choosing a product solely based on initial aesthetic appeal.
Authors
Gry Alfredsen Geir Wæhler Gustavsen Lone Ross Jonas Niklewski Philip Bester van Niekerk Christian BrischkeAbstract
To optimise the use of renewable materials in construction, it is essential to understand the factors influencing decisions throughout their design and service life. Life Cycle Costing (LCC) supports sustainable development by aiming to minimise long-term costs through informed planning of service life, maintenance, and replacement. Central to this is the engineering concept of limit states - Ultimate Limit States (ULS) for structural safety and Serviceability Limit States (SLS) for functionality. However, in non-loadbearing applications such as cladding, maintenance is often driven by aesthetic deterioration rather than structural concerns. These aesthetic limit states are subjective and influenced by user preferences, personality traits, and cultural background. In practice, undesired aesthetic changes are among the main reasons for cladding replacement in Europe, alongside fungal decay and modernisation. Premature replacement due to insufficient communication about weathering effects and maintenance needs remains under-addressed. By accounting for variation in user preferences, material selection can be tailored to support a longer service life. This study presents multi-country variation in climate-related perceptions of wood and user preferences for wooden cladding.