Wood-cement Composites Research Articles

Study of the Effect of Cedar Sawdust Content on Physical and Mechanical Properties of Cement Boards.

The growing demand for sustainable building materials, amid escalating costs, has spurred interest in alternative solutions such as wood cement composites. This study explores the feasibility of producing wood cement boards (WCBs) using locally sourced cedar sawdust as a reinforcing agent. Boards with a thickness of 10 mm and a target density of 1200 kg/m3 were manufactured under pressures ranging from 2 to 6 MPa for 24 h. Cedar sawdust, used as raw and untreated material, was incorporated into the mixture as a partial substitute for cement in varying proportions, ranging from 10% to 25% (by weight). The WCBs were cured for 28 days under ambient conditions. Physical properties including density, water absorption (WA), and thickness swelling (TS) were assessed, along with mechanical properties through flexural tests. The results showed that increasing cedar sawdust content decreased both density and mechanical performance while increasing WA and TS. Microstructural analysis (SEM and EDS) revealed significant porosity at higher sawdust contents, while lower contents had better matrix-reinforcement cohesion. Additionally, substantial levels of calcium and silicon were detected on the sawdust surface, indicating stabilized cement hydration products. These findings, supported by thermal (TGA and DSC) and FTIR analyses, clearly demonstrate that cement boards with 10% cedar sawdust exhibit favorable properties for non-structural applications, such as wall and partition cladding.

Study on wood chips modification and its application in wood-cement composites

Wood-cement composites have the advantages of high flexural strength, toughness, and impact resistance. However, the components such as hemicellulose and lignin in the wood chips can inhibit cement hydration, and thus the interface bonding between wood chips and cement matrix is poor. In order to address these issues, alkali cooking (mass concentration is 2–8%) and silane coupling agent (mass concentration is 1–5%) were used in this study to modify wood chips, and the resulting compressive and flexural strengths of wood-cement composites prepared from different kinds of modified wood chips were evaluated. Further, the XRD, SEM, and FT -IR tests were carried out to characterize the modified wood chips and explore the mechanism of modified wood chips incorporated composites. The results showed that the alkali cooking agent could effectively remove amorphous components, such as hemicellulose and lignin, from wood chips, improve crystallinity and relative cellulose content, and increase the surface roughness of wood chips. The silane coupling agent could chemically bond with wood chips to improve the interfacial properties between wood chips and cement matrix. The flexural strength of the composites prepared with wood chips treated with 3% silane coupling agent and 4% alkali cooking agent was increased, which was 11.9% higher than that of the composites prepared from wood chips treated only with 4% alkali cooking agent, while it was 27.1% and 31.6% higher than the composites prepared with untreated wood chips and mortar without wood chips, respectively. Alkali cooking modification and silane coupling agent treatment of wood chips can effectively improve the mechanical properties of composite materials.

Evaluation of Effective Elastic Properties for Wood–Cement Composites: Experimental and Computational Investigations

In this work, wood–cement composites (WCC) based on poplar sawdust were developed and fabricated by the extrusion process. The volume fraction of wood particles in the mixes was varied from 23% to 46%. The mechanical properties of these WCC were characterized in compression to determine the maximum compressive strength and the Young’s modulus. In the second part, these Young’s modulus values were estimated in compression using a 3D numerical homogenization which takes into account the variability in wood particle lengths and the random distribution in the mixes. The obtained results show a good agreement between the experimental data and numerical calculations up to a 35% volume fraction. The model’s poor estimation for large volume fractions (over 35%) could be attributed to the experimental sample size, which is not representative for large volume fractions, the percolation of the wood particles into the mixes and the inhibition of the cement setting.

Прочность древесно-цементного композита при воздействии химических добавок на заполнитель

The work is devoted to the study of the dependence of the strength of a wood-cement composite on the type of chemical additives used to neutralize the water-soluble substances contained in the wood filler (sugar, starch, tannins, gum, phenol, organic acids) that negatively affect the processes of hydration and hardening of cement. Chemical additives were used in the work ‒ forming hardly soluble compounds with sugars, accelerating the hardening of cement, forming mineral films on the surface of wood particles. An increase in the strength of a wood-cement composite was experimentally established with the introduction of a complex additive consisting of 1 % CaCl2 and 1 % ScSl2. It is determined that salts of arsenic and chromic acids also have a positive effect on increasing the strength characteristics of wood-cement composite. The use of hydrofluoric acid salt for the production of wood-cement composite can significantly increase the biological resistance of wood-cement composite. Combined chemical additives accelerating the hardening of wood-cement composite — aluminum chloride, sodium sulfate, ammonium nitrate and sodium metalluminate — have been established. The types and costs of the most effective chemical additives combining calcium chloride, liquid glass, aluminum sulfate, lime and ethanolamines for various types of wood are determined. The experiments carried out confirmed the previously obtained data that the strength of the wood-cement composite is influenced not only by the combination of various chemical additives, but also by the order of their introduction into the wood-cement composite.

Wood-Cement Composite and its Reinforcement with Wooden Bars

The task of reducing the negative environmental impact of industrial production and human economic activity is a prerequisite for the development of energy-saving technologies and materials based on industrial and household waste. The technology for the production of wood-cement composite materials is of great importance from an engineering point of view, as well as the technology for wood waste disposal, which has environmental attractiveness. Wood-cement composites are used as heat-insulating and structural materials. At the same time, one of the factors limiting their wide distribution is insufficient bearing capacity. In the course of the research, the strength indicators of building blocks made of wood-cement composite were determined, provided they were reinforced with wooden bars. The authors also concentrated on the thermal efficiency factors influenced by the presence of a block of reinforcing elements in the massif. The study was carried out by means of a physical experiment using Elcut software package. The resulting increase in strength during reinforcement amounted to 27 ... 31% or 3.1 ... 3.22 MPa with the initial strength indicators of the unreinforced block - 2.44 MPa. The volume of the resistance to heat transfer of the block made of a wood-cement composite during its reinforcement practically does not change. The results obtained can be used in the design and operation of building structures.

The influence of mineral inclusions on the heat efficiency of the enclosing construction from wood-cement composite in the rural house building

Reducing the cost of maintaining housing objects inevitably leads to the development of energy-saving technologies and building materials. Cost reduction is achieved by reducing heat losses through walls and floors of buildings and structures. Wood-cement composite materials are attractive not only from the point of view of energy saving and reducing construction costs, but also as materials in the production of which woodworking waste is used, therefore, the problem of complex waste-free use of raw materials is solved. In the course of the research, the influence of mineral inclusions on the indicators of the thermal efficiency of enclosing structures made of wood-cement composite (wood concrete and sawdust concrete) was determined. The work was based on the use of physical modeling methods (finite element method) implemented in the Elcut software package. The value of the heat loss indicator, depending on the type of wood-cement composite and operating conditions, was 34.2…. 54.8 W/(m2·°C). The indicator of resistance to heat transfer is 0.58 … 2.2 (m2·°C)/W. The presence of mineral inclusions worsens the thermal performance of the enclosing structure by an average of 7%. The results obtained can be used in the design and operation of building structures made of wood-cement composites.

Treatments of residual pine strands: characterization and wood-cement-compatibility

This paper aims to evaluate treatments on pine strands as well as wood-cement compatibility. The strands were prepared and then were submitted to four treatments (untreated; cold water, hot water and NaOH). Physical, chemical, thermal and mechanical properties of the strands were measured. Wood-cement composites were produced with all strand treatments. To evaluate the strand effects on the cement hydration, axial compression tests were conducted at 28-day. The phases of the matrix of the composites at 24 h 7- and 28-day were also determinate. Fourier transform infrared spectra shows that, although the treatments partially removed the hemicellulose and extractives, they also reduced the cellulose and lignin bands. Axial compression results indicated that there were no differences between values for the composites with untreated and treated strands. For the phase analyses, in the initial ages (24 h and 7-day), it was identified that portlandite for cement sample (control) is higher than those containing the strands. At 28-day, it was found that among the strands, the untreated have the lower portlandite content and the higher calcium carbonate content. Indicating the cement carbonation over time as presented in the cement sample (control). Therefore, the untreated pine residual strand showed good compatibility with cement and for this study there were no benefits on treating the strands.

Enhanced Resistance to Fire of the Bark-Based Panels Bonded with Clay

The aim of this study was to investigate the flammability of ecologically friendly, 100% natural larch and poplar bark-based panels bonded with clay. The clay acted as a fire retardant, and it improved the fire resistance of the boards by 12–15% for the surface and 27–39% for the edge of the testing specimens. The thermal conductivity was also analyzed. Although the panels had a density ranging from 600 to 900 kg/m3, thermal conductivity for the panel with a density of 600 kg/m3 was excellent, and it was comparable to lightweight insulation panels with much lower densities. Besides that, the advantage of the bark clay boards, as an insulation material, is mostly in an accumulative capacity similar to wood cement boards, and it can significantly improve the climatic stability of indoor spaces that have low ventilation rates. Bark boards with clay, similar to wood cement composites (wood wool cement composites and wood particle cement composites), have low mechanical properties and elasticity. Therefore, there their use is limited to non-structural paneling applications. These ecologically friendly, 100% natural and recyclable composites can be mostly used with respect to their thermal insulation, acoustics and fire resistance properties.

Editorial

Editorial

Studies on the durability of wood-cement particleboards produced with residues of Pinus spp., silica fume, and rice husk ash

Wood-cement composites were considered as substitutes for wood or asbestos cement. This research is focused on the development, characterization, and durability of different wood-cement particle boards composed of wood waste [residual particles of pine species (Pinus spp.)], with silica fume or rice husk ash. The wood-cement panels produced by cold compression were evaluated for their physical and mechanical properties after accelerated and natural weathering for 28 and 91 days of curing, respectively. Results indicate that the performance of wood-cement panels containing the Pinus spp. residue was comparable to that of lignocellulosic aggregate in wood cement panels. Pine residue wood panels exhibited high levels of pozzolanic activity, suggesting that silica fume or rice husk ash could be used as a partial substitute in Portland cement. There was a significant loss of mechanical properties over time with both the reference panel and the panel produced with pozzolana. Although there was no direct correlation between the values of accelerated weathering tests and natural weathering tests, there was a larger degradation of the panels after 20 cycles of the accelerated weathering than that after 12 months of natural weathering. Morphology studies supported the observed results.

About the Possibility of Recycling Water Treatment Sludge in the Wood–Cement Composites Production

The paper presents the results of a study of the possibility of recycling water treatment sludge in the production of wood-cement composites. Sludge is formed during the treatment of sewage, containing industrial machine oil, with a sorption material, based on thermally modified chestnut tree waste (CTW). It was found that the addition of sludge leads to an increase in the density of the samples. Thus, the samples without the addition of sludge have an average density of 860 kg/m3, samples with the addition of sludge in an amount of 10 mass% - 875 kg/m3, 20 mass% - 879 kg/m3, 30 mass% - 882 kg/m3, 42 mass % - 887 kg/m3. Studies of the change in water absorption of samples, depending on the amount of sludge added, showed that the values slightly decrease for samples containing sludge, what is explained by the presence of oil in the mixture. The compressive strength of the samples with the addition of sludge in the amount of 42 mass% was 3.1 MPa, what corresponds to the regulatory requirements for a wood cement composites.

The dynamics of the decrease in the strength of wood-cement compositions in soil conditions

The intensive felling of plantations, in the process of logging, leads to a decrease in the forest area, reducing their quality. Natural and artificial reforestation is the work aimed at compensating the reduction of forest area. Reforestation with seedlings with a closed root system in containers is a modern trend used worldwide. The article is devoted to the study of the properties of wood-cement composite material in relation to the possibility of its use for the manufacture of biodegradable planting containers, mainly for large-sized planting material. As a result of experimental studies, strength properties and dynamics of their decrease depending on the time of the material in natural soil conditions are determined. The reduction of the compressive strength of the material from 3.36 MPa to 1.65 MPa for 42 months was found.

The Influence of Chemical Additives on Strength of Wood-Cement Composite

The strength and strains of the wood-cement composite primarily depend on the main technоlogical factors such as the used type of binder and wood filler, the method of wood filler preparation, the method of molding, the conditions of hardening. The aim of this work is an experimental study of the chemical additives influence on wood filler to localize the harmful effects of water-soluble wood substances on the processes of hydration and hardening of cement. Using the additives, it is possible to achieve satisfactory strength parameters even on green wood. The maximum strength was obtained when complex chemical additives were applied. The most effective additives involved calcium chloride, liquid glass, aluminum sulfate, lime and ethanolamines. The optimal consumption and ratio of the complex additives components costs also depend on the degree of preliminary wood exposure.

Influência de aditivos químicos na produção de compósitos madeira-cimento de duas espécies tropicais da Amazônia

Este trabalho teve como objetivo avaliar o potencial de uso de três diferentes aditivos químicos (CaCl2, MgCl2 e cal hidratada) na produção de compósitos madeira-cimento manufaturados com a mistura de partículas de madeira de costaneira de piãozinho (Eschweilera coriaceae (DC.) Mart) e matá-mata-branco (Eschweilera odora (poepp.) Miers) e cimento Portland tipo CP II-Z, na razão 1:2,75, pelo método de adensamento por vibrocompactação. Teste de compatibilidade entre a madeira e cimento mostrou que essas espécies são aptas para a produção de compósitos quando pré-tratadas com o uso de aditivos químicos na mistura. Com base nos resultados, pode-se concluir que: (I) As espécies do gênero Eschweilera estudadas são aptas para produção de compósitos madeira-cimento, sendo que compósitos produzidos com a madeira de piãozinho (Eschweilera coriaceae) obtiveram melhores resultados; (II) A adição de CaCl2 teve efeito positivo nas propriedades mecânicas dos compósitos de Eschweilera coriaceae; e (III) Não é recomendável o uso de cal hidratada como aditivo químico quando o método utilizado é o de vibrocompactação.

Alternative vibro-dynamic compression processing of wood-cement composites using Amazonian wood

ABSTRACT Wood-cement composite (WCC) is a potential construction material for tropical regions, due to its physico-mechanical properties and resistance to decay and fungi attack. However it is important to test alternative production methods and wood materials that are easier and cheaper than those traditionally used, in order to create a higher demand for this product. The aim of this work was to evaluate the use of wood from four Amazonian species (Eschweilera coriaceae, Swartzia recurva, Manilkara amazonica and Pouteria guianensis) in the production of wood-cement composites through a vibro-dynamic compression process, an alternative method to the use of a hydraulic press. The inhibition degree caused by the wood to the cement cure, measured by the factor CA, indicated that all species were compatible with Portland cement (CP II-Z). WCC with densities higher than 1,100 kg m-3 (produced with E. coriaceae and S. recurva particles) showed compressive strength values higher than 10 MPa, which fulfills the minimum requirement for lightweitgh reinforced concrete blocks for structural use.

MSWI bottom ash as binder replacement in wood cement composites

Nowadays, the incineration of municipal solid waste (MSW) is widely applied, as it reduces the waste 90% by volume and 80% by mass. The main by-product coming from the MSW incineration is bottom ash (BA). Despite numerous studies concerning the uses of this by-product in the construction field, BA is not widely applied because of two main concerns: (1) the disadvantageous morphology of the particle, leading to a high porosity and water absorption and (2) the presence of harmful contaminants, leaching out from the by-product. Because of its porous structure, BA can be suitable as binder replacement for improving insulation properties of wood composites, usually requiring low flexural strength. Therefore, this study will evaluate the influence of a porous binder containing BA and cement on wood wool cement boards (WWCB). The BA and cement are chemically and physically characterized. Thereafter, cement pastes with different replacement levels of BA (0–50%) are produced to measure mechanical and thermal properties. The same mixes are then used to make WWCB. While the thermal conductivity remains unchanged, the mechanical properties benefit from the use of BA up to 30% wt. due to the reduced macro porosity of the final composite.

Structural response of cement-bonded wood composite panels as permanent formwork

Bio-sourced materials combined with a cementitious matrix offer an interesting alternative to traditional construction materials. To contribute to their wider acceptance by the sustainable construction market, an investigation into the use of wood-cement composite panels as stay-in-place or permanent formwork is presented. As individual panels, the mechanical performance was evaluated through three point bending tests. But, as part of the formwork system, their overall structural performance was evaluated through finite element simulation under the action of lateral pressure exerted by the concrete in a liquid state. The Concrete Damage Plasticity Model (CPDM) available in the Abaqus code is adapted and used to model the mechanical behaviour of the wood-cement composite. The obtained results show wood-cement composite panels offer a promising alternative for the development of a lightweight permanent formwork system, that can contribute to the thermal and acoustic comfort of green buildings.

Particle Sizes and Wood/Cement Ratio Effect on the Production of Vibro-compacted Composites

The aim of this study was to evaluate the influence of particle size and the wood/cement ratio on the physical and mechanical properties of vibro-compacted wood-cement composites. The effects of three different particle sizes (diameter between 1.4-2.36 mm; 2.36-4 mm; and 4-9.56 mm) and wood:cement ratios of 1:2.75, 1:2 and 1:1.5 on wood-cement composites produced with the Amazonia species Swartzia recurva Poepp. and Portland cement type II-Z were analyzed. All evaluated properties were influenced by the particle size used in the mixture; however, the wood:cement ratio only affected the final density of the composite, internal bond and water absorption properties. Composites produced with particles that pass through a 2.36 mm screen but were retained with a 1.4 mm screen showed average values of modulus of rupture and higher modulus of elasticity than composites produced with bigger particles. The use of a 1:2.75 wood:cement ratio resulted in composites with higher density and dimensional stability than composites produced with a lower amount of cement.

Morphological Approach for Nonlinear Flow and Heat Transfer in Complex Bio-Composite Material

ABSTRACTThe bio-based materials have experienced in recent years a relevant evolution in construction and for many building applications. Despite the efforts to develop new solutions to achieve the objectives of numerical characterizations, a few researches in this area have been carried out using a heterogeneous wood-cement composite. This study is based on a constructive approach using the finite volume method in order to generate a numerical model capable of reproducing the equivalent transfer properties of a wood-cement composite. The challenge is to understand, design, and control this multiphase inhomogeneous structure and predict transfers and flows within the community in order to achieve an optimal functionality. Experimental measurements and microscopic characterization using X-ray microtomography were performed to compare and demonstrate the method validation. The comparative results demonstrate a less than 10% deviation between the measurements and the simulations of the equivalent thermal properties. Thus, thermal conductivity and permeability, under different medium configurations, were characterized. Therefore, it was observed that these properties depend strongly on the porosity and the pore distribution in the continuous phase. Moreover, these two parameters are highly dependent on cement percentages in the structure.

Influence of the spruce strands hygroscopic behaviour on the performances of wood-cement composites

In wood wool cement composites, the influence of natural fibres is the main factor leading to the instability of the final product. During the manufacture, small variations in wood properties result in inhomogeneous density and strength of the boards. Among the accountable factors, the hygroscopic behaviour of the wood can deeply affect the cement hydration. However, the competitive water absorption mechanism between wood strands and cement is not fully understood. This paper will address the absorption behaviour of wood wool strands in combination with cement. A model for calculating the water to binder ratio of the paste in presence of wood is proposed and validated by NMR and isothermal calorimetry. Finally, the mechanical performances of the composites are tested for different water amounts, verifying the proposed model and defining the conditions for the optimal bending strength.