Search Results (71)

This study presents a cost-effective, carbon-negative construction material for affordable housing, developed entirely from locally available agricultural wastes: rice husk ash, wood ash, and rice straw—materials often problematic to dispose of in many African regions. Rice husk ash provides high amorphous silica, acting as a strong pozzolanic agent. Wood ash contributes calcium oxide and alkalis to serve as a reactive binder, while rice straw functions as a lightweight organic filler, enhancing thermal insulation and indoor climate comfort. These materials undergo natural pozzolanic reactions with water, eliminating the need for Portland cement—a major global source of anthropogenic CO₂ emissions (~900 kg CO₂/ton cement). This process is inherently carbon-negative, not only avoiding emissions from cement production but also capturing atmospheric CO₂ during lime carbonation in the hardening phase. Field trials in Kenya confirmed the composite’s sufficient structural strength for low-cost housing, with added benefits including termite resistance and suitability for unskilled laborers. In a collaboration between the University of Tartu and Kenyatta University, a semi-automatic mixing and casting system was developed, enabling fast, low-labor construction of full-scale houses. This innovation aligns with Kenya’s Big Four development agenda and supports sustainable rural development, post-disaster reconstruction, and climate mitigation through scalable, eco-friendly building solutions. Full article

Recycled wood fiber (RWF) obtained through the multi-stage processing of waste wood serves as an eco-friendly green construction material, exhibiting lightweight, porous, and high toughness characteristics that demonstrate significant potential as a cementitious reinforcement, offering strategic advantages for environmental protection and resource recycling. In this study, high-performance sulfoaluminate cement (SAC)-RWF composites prepared by modifying RWFs with nano-silica (NS) and a silane coupling agent (KH560) were developed and their effects on mechanical properties, shrinkage behavior, hydration characteristics, and microstructure of SAC-RWF composites were systematically investigated. Optimal performance was achieved at water–cement ratio of 0.5 with 20% RWF content, where the KH560-modified samples showed superior improvement, with 8.5% and 14.3% increases in 28 d flexural and compressive strength, respectively, compared to the control groups, outperforming the NS-modified samples (3.6% and 8.6% enhancements). Both modifiers improved durability, reducing water absorption by 6.72% (NS) and 7.1% (KH560) while decreasing drying shrinkage by 4.3% and 27.2%, respectively. The modified SAC composites maintained favorable thermal properties, with NS reducing thermal conductivity by 6.8% through density optimization, whereas the KH560-treated specimens retained low conductivity despite slight density increases. Micro-structural tests revealed accelerated hydration without new hydration product formation, with both modifiers enhancing cementitious matrix hydration product generation by distinct mechanisms—with NS acting through physical pore-filling, while KH560 established Si-O-C chemical bonds at paste interfaces. Although both modifications improved mechanical properties and durability, the KH560-modified SAC composite group demonstrated superior overall performance than the NS-modified group, providing a technical pathway for developing sustainable, high-performance recycled wood fiber cement-based materials with balanced functional properties for low-carbon construction applications. Full article

Costa Rica is located along the narrow isthmus that connected South America to North America beginning in the mid-Cenozoic. The exchange of vertebrates between the two continents has received considerable study, but paleobotanical aspects are less known. The Pacific coast “ring of fire” volcanoes produced abundant hyaloclastic material that provided a source of silica for wood petrifaction, and the tropical forests contained diverse taxa. This combination resulted in the preservation of petrified wood at many sites in Costa Rica. Fossil wood ranges in age from Lower Miocene to Middle Pleistocene, but Miocene specimens are the most common. Our research involved the study of 54 specimens, with the goal of determining their mineral compositions and interpreting the fossilization processes. Data came from thin-section optical microscopy, SEM images, and X-ray diffraction. Two specimens were found to be mineralized with calcite, but most of the woods contained crystalline quartz and/or opal-CT. The preservation of anatomical detail is highly variable. Some specimens show evidence of decay or structural deformation that preceded mineralization, but other woods have well-preserved cell structures. This preliminary study demonstrates the abundance and botanical diversity of fossil wood in Costa Rica, hopefully opening a door into future studies that will consider the taxonomy and evolutionary aspects of the country’s fossil forests. Full article

Optical microscopy and SEM imaging are powerful tools for evaluating the origins of quartz in fossil wood. Silicification is the most common mechanism for wood petrifaction, but this silica is commonly in cryptocrystalline or microcrystalline form (e.g., chalcedony or agate). Two essential requirements for the formation of macrocrystalline quartz is a concentration of dissolved silica low enough to allow the development of well-ordered lattices, and sufficient open space to allow euhedral or subhedral crystals to grow. Macrocrystalline quartz commonly occurs as a late-stage precipitate in open spaces that remained after initial mineralization had occurred. These spaces include vessels in angiosperm wood, and vugs and fractures in all types of wood. Exterior surfaces may also be suitable sites for quartz crystal growth. In some occurrences, crystalline quartz has directly encrusted or replaced wood cells. Diagenetic transformation of opal can produce cryptocrystalline or microcrystalline forms of quartz, but this process is not likely to produce macrocrystals. Full article

As new technologies are developed, the demand for rare earth elements (REEs) has increased, despite limited awareness of their significant impact on people and the environment. In this study, waste fly ash was used as a precursor to synthesize inorganic aluminosilicate polymers by adding an activator to the alumina and silica compounds of the ash. Due to their structure and adsorption potential, their application for the removal of selected REEs (Gd³⁺, Y³⁺, and Sc³⁺) from water has been investigated. A decrease in the intensity of the quartz peak at 2θ of 26.6° in the XRD spectrum and the disappearance of the albite and mullite peaks due to dissolution during alkaline activation in both modified samples were observed. The appearance of a peaks at 2θ of 29.3° and 39.3° corresponding to calcite in the modified sample indicates the presence of wood ash. A shifting of the band in the DRIFT spectrum to 1030 cm⁻¹ on the spectra of modified samples corresponds to the vibrations of Al-O and Si-O bonds and the formation of a polymeric network structure (Si-O-Si or Si-O-Al). According to pH_PZC values, thermodynamic and kinetic parameters, and chemical composition, the presumed mechanism of REE adsorption is chemisorption and ion exchange. The highest adsorption efficiencies (up to 95%) for all examined REEs in both single and mixed REE solutions were obtained from an alkali-activated mixture of fly ash and wood ash. The results of this research are significant for expanding knowledge about the removal of REEs from the environment, the reduction of waste ash by their modification, and their potential subsequent use in construction as additives. Full article

This study explores the potential of using underutilized materials from agricultural and forestry systems, such as rice husk, wheat straw, and wood strands, in developing corrugated core sandwich panels as a structural building material. By leveraging the unique properties of these biobased materials within a corrugated geometry, the research presents a novel approach to enhancing the structural performance of such underutilized biobased materials. These biobased materials were used in different lengths to consider the manufacturing feasibility of corrugated panels and the effect of fiber length on their structural performance. The average lengths for wood strands and wheat straws were 12–15 cm and 3–7.5 cm, respectively, while rice husks were like particles, about 7 mm long. Due to the high silica content in rice husk and wheat straw, which negatively impacts the bonding performance, polymeric diphenylmethane diisocyanate (pMDI), an effective adhesive for such materials, was used for the fabrication of corrugated panels. Wood strands and phenol formaldehyde (PF) adhesive were used to fabricate flat outer layers. Flat panels were bonded to both sides of the corrugated panels using a polyurethane adhesive to develop corrugated core sandwich panels. Four-point bending tests were conducted to evaluate the panel’s bending stiffness, load-carrying capacity, and failure modes. Results demonstrated that sandwich panels with wood strand corrugated cores exhibited the highest bending stiffness and load-bearing capacity, while those with wheat straw corrugated cores performed similarly. Rice husk corrugated core sandwich panels showed the lowest mechanical performance compared to other sandwich panels. Considering the applications of these sandwich panels as floor, wall, and roof sheathing, all these panels exhibited superior bending performance compared to 11.2 mm- and 17.42 mm-thick commercial OSB (oriented strand board) panels, which are commonly used as building materials. These sandwich structures supported a longer span than commercial OSB panels while satisfying the deflection limit of L/360. The findings suggest the transformative potential of converting renewable yet underutilized materials into an engineered concept, corrugated geometry, leading to the development of high-performance, carbon-negative building materials suitable for flooring and roof applications. Full article

Compositional and anatomical studies of silicified wood have been carried out extensively all around the world. The classification of silicified wood as such deals with all the forms and phases of silica that come under its umbrella. One such class of silicified wood is fossil wood with a high content of quartz, and there are very limited mentions of this category of fossilized wood. The examined wood belongs to gymnosperm and comes from the Upper Triassic deposits of Madagascar. A fresh approach to such samples is adopted by studying the crystallographic texture of the fossil wood to understand the orientation of the crystals replacing the organic matter within the sample. This work focuses on crystallographic texture analysis based on pole figures measured by X-ray diffraction. The intensity of the pole density maxima on the pole figures measured on the heartwood surface part of the analyzed samples is higher than that on the sapwood. This affirms that the crystallographic texture is sharper at the heartwood part compared to the sapwood. The X-ray tomography study, conducted to understand the difference in mineral distribution within the sample, reveals a greater X-ray absorbing phase on the sapwood of both samples. This is due to the concentration of iron compounds, which both replace the remaining conductive structures of the wood and fill the cavities inside them. We believe that this research on silicified wood is the first research work that encompasses crystallographic texture analysis with pole figures, an approach not previously undertaken in similar studies. We hope that our research can be useful in understanding the processes of replacement of organic matter by minerals. Full article

Wood is a valuable material with incomparable advantages, though it is susceptible to biotic and abiotic factors action that affect it adversely and shorten its service life. In the current study, the surface modification of oak wood is carried out through brief immersion in a solution of acrylic polymer Paraloid B72, in which silica dioxide nanoparticles in the form of nanopowder were dissolved at different contents (1, 2, 3, and 4% w/v of the solution) aiming at the elimination of wood material hygroscopicity, and the protection and improvement of other properties. Specifically, the modified and unmodified wood specimens were characterized in terms of physical characteristics (density, equilibrium moisture content, colour, and surface roughness), hygroscopic properties (swelling and absorption percentage) and accelerated weathering performance using xenon light and cycles of moisturizing and drying. The results revealed the dimensional stability of the samples and a significant increase in the hydrophobicity of the modified wood, as well as a significant increase in the resistance to the ageing/weathering factors of oak wood, which was proportional to the increase in the presence of nanoparticles in the Paraloid B72 solution. The colour of the treated samples slightly changed towards darker shades, more reddish and yellowish (with L* to decrease, while a* and b* to slightly increase), though the treated wood revealed higher colour stability. The surface roughness parameters (Ra, Rq, and Rz) increased significantly, restricting the wide application of the treated wood in indoor or outdoor applications where surface roughness constitutes a critical factor. The findings of the current work contribute not only to the production of longer-lasting wood and timber structures, but also to the conservation of the existing weathered heritage timber structures. Full article

This research addresses a notable gap in understanding the synergistic effects of high carbon wood bottom ash (BA) and silica fly ash (FA) on cement hydration and concrete durability by using them as a supplementary material to reduce the amount of cement in concrete and CO₂ emissions during cement production. This study analyses the synergistic effect of FA and BA on cement hydration through X-ray diffraction (XRD), thermal analysis (TG, DTG), scanning electron microscopy (SEM), density, ultrasonic pulse velocity (UPV), compressive strength, and temperature monitoring tests. In addition, it evaluates concrete properties, including compressive strength, UPV, density, water absorption kinetics, porosity parameters, predicted resistance to freezing and thawing cycles, and results of freeze–thawing resistance. The concrete raw materials were supplemented with varying percentages of BA and FA, replacing both cement and fine aggregate at levels of 0%, 2.5%, 5%, 10% and 15%. The results indicate that a 15% substitution of BA and FA delays cement hydration by approximately 5 h and results in only a 6% reduction in compressive strength, with the hardened cement paste showing a strength similar to a 15% replacement with FA. Concrete mixtures with 2.5% BA and 2.5% FA maintained the same maximum hydration temperature and duration as the reference mix. Furthermore, the combined use of both ashes provided adequate resistance to freeze–thaw cycles, with only a 4.7% reduction in compressive strength after 150 cycles. Other properties, such as density, UPV and water absorption, exhibited minimal changes with partial cement replacement by both ashes. This study highlights the potential benefits of using BA and FA together, offering a sustainable alternative that maintains concrete performance while using waste materials. Full article

In this thesis, wood loaded with a silica–titanium (Si-Ti) composite film was prepared using the sol–gel method in order to achieve improved wood with high hydrophobicity and photocatalytic activity under visible light. The factors affecting the structure and properties of the composite film, as well as the optimization process, were discussed. Infrared analysis revealed that the vibrational intensity of Si-O-Si, Ti-O-Ti, and Ti-O-Si telescopic vibration peaks increased with an increase in vinyltriethoxysilane (VETS). Additionally, the number of Ti-O-Ti telescopic vibration peaks also increased with an increase in VETS. Furthermore, the intensity of -NO₃, Si-O-Si, and Ti-O-Ti telescopic vibrational peaks was enhanced with a higher dosage of nitric acid. Conversely, the intensity of -OH telescopic vibrational peaks decreased with an increase in drying temperature. XRD analysis showed that nitric acid could promote the transformation of TiO₂ from amorphous to anatase, while SiO₂ would reduce the grain size of anatase TiO₂ and promote the growth of rutile TiO₂. Additionally, wood surfaces loaded with Si-Ti composite film changed from hydrophilic to hydrophobic, with significant differences observed between different levels of each factor. The photocatalytic activity of surface-loaded Si-Ti composite films on wood was most affected by the amount of nitric acid, which influenced crystallinity of TiO₂ and thus impacted the photocatalytic activity. Furthermore, changes in VTES dosage not only affected the crystalline phase of TiO₂ and the grain size of Si-Ti composite film but also influenced the crystallinity of TiO₂ through generating SiO₂. Finally, based on optimal preparation process (titanium–alcohol ratio of 1:5, titanium–silicon ratio of 1:0.2, titanium–acid ratio of 1:0.5, and drying temperature of 100 °C), wood surfaces loaded with Si-Ti composite film achieved a contact angle up to 125.9° and exhibited a decolorization rate for rhodamine B under UV light reaching 94% within 180 min. Full article

The efficient exploitation of planted fast-growing wood is crucial for enhancing wood resource utilization. In this study, the fast-growing poplar wood was modified by in situ impregnation through vacuum impregnation with polyvinyl alcohol and nano-silica sol as impregnation modifiers, combined with delignification–freezing pretreatment. The samples were characterized by FTIR, XRD, SEM, and the universal mechanical testing machine. The results showed that the wrinkle deformation and cracking of the wood blocks were greatly alleviated after the delignification–freezing pretreatment and the polyvinyl alcohol and nano-silica sol were successfully integrated into the wood. The resulting polyvinyl alcohol–silica sol poplar composites exhibited about 216%, 80% and 43% higher compressive strength with respect to delignified wood, natural wood and impregnated natural wood, respectively, thereby demonstrating superior mechanical properties and potential opportunities for value-added and efficient utilization of low-quality wood. Full article

As a renewable, environmentally friendly, natural, and organic material, wood has been receiving extensive attention from various industries. However, the hydrophilicity of wood significantly impacts the stability and durability of its products, which can be effectively addressed by constructing superhydrophobic coatings on the surface of wood. In this study, tung oil, carnauba wax, and silica nanoparticles were used to construct superhydrophobic coatings on hydrophilic wood surfaces by a facile two-step dip-coating method. The surface wettability and morphology of the coatings were analyzed by a contact angle meter and scanning electron microscope, respectively. The results suggest that the coating has a micron–nanosized two-tiered structure, and the contact angle of the coating is higher than 150° and the roll-off angle is lower than 10°. Sandpaper abrasion tests and UV diffuse reflectance spectra indicate that the coatings have excellent abrasion resistance and good transparency. In addition, the coated wood shows excellent self-cleaning and water resistance, which have great potential for applications in industry and furniture manufacturing. Full article

This study introduced a novel two-step treatment to enhance the waterproofing, dimensional stability, and self-cleaning capabilities of ancient architectural wood. The process was initiated with the immersion of wood in an organic hybrid sol, composed of an acidic methyltrimethoxysilane (MTMS)-based silica sol and polyvinyl alcohol (PVA), which effectively sealed the wood’s inherent pores and cracks to mitigate degradation effects caused by aging, fungi, and insects. Subsequently, the treated wood surface was modified with an alkaline MTMS-based silica sol to form a functional superhydrophobic protective layer. The modification effectiveness was meticulously analyzed using advanced characterization techniques, including scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The results demonstrated substantial improvements: the modified wood’s water contact angle (WCA) reached 156.0°, and the sliding angle (SA) was 6.0°. Additionally, the modified wood showed a notable reduction in water uptake and moisture absorption, enhancing its dimensional stability. The superhydrophobic surface endowed the wood with excellent self-cleaning properties and robust resistance to pollution. Enhanced mechanical durability of superhydrophobic surface was observed under rigorous testing conditions, including sandpaper abrasion and tape peeling. Furthermore, the modification improved the thermal stability, compressive strength, and storage modulus of the wood. Collectively, these enhancements render this modification a potent methodology for the preservation and functional augmentation of historic architectural woodwork. Full article

Nowadays, the protection of wood is becoming more important with the increasing demand for durable wood, in addition to its limited accessibility. One possible way to increase the durability is the use of nanoparticles, which can be effective even with a low intake of active ingredients. However, avoiding their leaching is a challenge. A possible solution to leaching is the use of silica aerogel as a fixative. This study investigated the use of mesoporous silica aerogel against the leaching of different nanoparticles under laboratory conditions. Tests were performed involving beech (Fagus sylvatica) and Scots pine (Pinus sylvestris) sapwood, using Trametes versicolor as a white rot and Coniophora puteana as a brown rot fungus. The results show that the subsequent treatment of the wood with mesoporous silica aerogel effectively fixed the nanoparticles in wood. The durability of the samples without aerogel significantly decreased as a result of leaching, whereas the resistance of the samples treated with aerogel decreased only slightly. However, the silica aerogel modification itself caused the leaching of silver nanoparticles, which is a limitation in the use of this method for the fixation of nanoparticles. Full article

In order to improve the hydrophobicity of the composite film on the wood surface, the wettability of the wood surface and its morphology, chemical structure, roughness and free energy changes were investigated in this paper after modification treatments with different volume fractions of octadecyltrichlorosilane (OTS) and polydimethylsiloxane (PDMS). It can be found that the water contact angle and surface roughness of the hydrophobically modified wood increased with the increase in volume fraction, but the overall effect of OTS hydrophobic modification was better than that of PDMS, and a maximum water contact angle of up to 140.8° could be obtained at a volume fraction of 2% of OTS. In addition, the intensity of the stretching vibration peak of -OH was weakened after the modification, while the intensity of the stretching vibration peak of -CH₂- was enhanced, resulting in an increase in hydrophobicity. At the same time, it can be found that the surface free energy of the modified wood specimens was reduced, which shows that OTS and PDMS improve the surface hydrophobicity of the wood by increasing the surface roughness and decreasing the surface free energy together. Finally, the hydrophobically modified Bi₂O₃-doped silica–titanium composite film still possessed high photocatalytic degradation activity for rhodamine B and gas formaldehyde, and the degradation rate could reach more than 90%. Full article