scholarly journals Evaluation of cement-bonded particleboards produced from mixed sawmill residues

2021 ◽  
Author(s):  
S. O. Amiandamhen ◽  
C. U. Agwu ◽  
P. N. Ezenwaegbu
Keyword(s):  
Mechanical Performance ◽  
Timber Species ◽  
Cement Composites ◽  
Wood Composite ◽  
Gmelina Arborea ◽  
Tropical Hardwood ◽  
Hardwood Species ◽  
Wood Residues ◽  
Screw Withdrawal ◽  
Composite Samples

AbstractThis study evaluates the application feasibility and properties of cement-bonded particleboards produced from mixed tropical hardwood species. Wood residues from a typical sawmill were collected, dried and used in the manufacturing of the cement composites. The wood residues used were from Ceiba pentandra and Gmelina arborea timber species. The residues were mixed in seven ratios in the production of the composite samples. Two control experimental samples containing unmixed residues of each species were also produced. The test carried out on the boards were flexural strength, water uptake properties and wet and dry screw withdrawal resistance. The effect of the wood mix ratio on the board properties was evaluated. The result showed that all properties except the screw withdrawal resistance were significantly influenced by the mix ratios (p < 0.05). The wet and dry screw withdrawal resistance ranged from 1170 to 1770 N and 1360 to 1830 N, respectively. The optimum wood mix ratio for enhancing mechanical performance of the boards was 1:4 of C. pentandra/G. arborea wood residues. Based on the result of this study, the particleboards produced can be used as wood composite ceiling tiles in building applications.

scholarly journals Impact of Prolonged Exposure of Eleven Years to Hot Seawater on the Degradation of a Thermoset Composite

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2154
Author(s):  
Amir Hussain Idrisi ◽  
Abdel-Hamid I. Mourad ◽  
Muhammad M. Sherif
Keyword(s):  
Exposure Time ◽  
Prolonged Exposure ◽  
Mechanical Performance ◽  
Matrix Cracking ◽  
Pull Out ◽  
Strength Based ◽  
Different Temperatures ◽  
River Line ◽  
Composite Samples

This paper presents a long-term experimental investigation of E-glass/epoxy composites’ durability exposed to seawater at different temperatures. The thermoset composite samples were exposed to 23 °C, 45 °C and 65 °C seawater for a prolonged exposure time of 11 years. The mechanical performance as a function of exposure time was evaluated and a strength-based technique was used to assess the durability of the composites. The experimental results revealed that the tensile strength of E-glass/epoxy composite was reduced by 8.2%, 29.7%, and 54.4% after immersion in seawater for 11 years at 23 °C, 45 °C, and 65 °C, respectively. The prolonged immersion in seawater resulted in the plasticization and swelling in the composite. This accelerated the rate of debonding between the fibers and matrix. The failure analysis was conducted to investigate the failure mode of the samples. SEM micrographs illustrated a correlation between the fiber/matrix debonding, potholing, fiber pull-out, river line marks and matrix cracking with deterioration in the tensile characteristics of the thermoset composite.

scholarly journals Using scanned images to estimate salt formation on the surface of cement composites

Vestnik MGSU ◽  
2020 ◽  
pp. 1523-1533
Author(s):  
Vladimir T. Erofeev ◽  
Victor V. Afonin ◽  
Tatiana F. Elchishcheva ◽  
Marina M. Zotkina ◽  
Irina V. Erofeeva
Keyword(s):  
Building Materials ◽  
Control Sample ◽  
Cement Composite ◽  
Operating Conditions ◽  
Cement Composites ◽  
High Humidity ◽  
Grayscale Image ◽  
Salt Formation ◽  
Scanned Images ◽  
Composite Samples

Introduction. An engineering method is proposed for assessing salt formation on the surface of cement composites exposed to adverse operating conditions. The technique is based on the histogram method used to determine the dominant brightness of the half-tone image of scanned cement composites. The criterion for ranking composites is a relative dimensionless value –– a metric obtained by comparing the brightness of a grayscale image with the brightness level of white. Materials and methods. We selected three types of compositions of composites in the amount of 21 items; each of them contains three samples –– a control sample and samples exposed to high humidity and positive temperatures for 15 and 45 days. Each composition is represented by a scanned raster image of the sample surface. The images are further subjected to digital processing using a software program written in the C++ programming language and the OpenCV technical vision library. This allows you to use the available methods and classes to develop algorithms to solve the problem in question and to convert a full-color RGB image to a grayscale image. Such images are used to analyze histograms, which determine the dominant level of brightness to determine the numerical metric for quantifying the salt formation on the surface of cement composite samples on the basis of their scanned images. Results. A description of the software algorithm, used to detect salt formation on the surface of cement composite specimens that have passed performance tests under high humidity conditions at positive temperatures, is presented. The method of ranking cement composite samples using the values of their dominant brightness relative to the brightness of control samples is shown. The comparative analysis of the study is presented in the form of numerical data and explanatory diagrams. Conclusions. Software modeling is employed to demonstrate the expediency of the methodology for the assessment of salt formation on the surface of cement composites and other building materials prone to salt formation.

scholarly journals Selección de Árboles Semilleros en Plantaciones Forestales de la Península de Santa Elena. Ecuador.

2017 ◽  
Vol 4 (2) ◽  
Author(s):  
Juan Valladolid Ontaneda ◽  
Ángel León Mejía ◽  
Daniel Paredes Flores
Keyword(s):  
Morphological Characteristics ◽  
Timber Species ◽  
Cedrela Odorata ◽  
Gmelina Arborea ◽  
Forest Species ◽  
Swietenia Macrophylla ◽  
Cordia Alliodora ◽  
Santa Elena ◽  
Number Of Seeds ◽  
Selection Of

El estudio de selección de árboles semilleros se realizó en las comunas Olón, Dos Mangas y Salanguillo del cantón Santa Elena, provincia de Santa Elena, Ecuador. El objetivo del estudio fue, identificar, caracterizar y seleccionar árboles semilleros de especies maderables con buenas características morfológicas, y que permitan disponer de semillas para trabajos de propagación de especies forestales en viveros con fines de reforestación. El estudio se inicia con la identificación y ubicación de plantaciones forestales de varias especies forestales establecidas entre los años 2000 a 2005, en las plantaciones se evaluaron las características dasométricas y morfológicas, las que permitieron seleccionar 11 árboles con características morfológicas deseables correspondientes a cinco especies forestales laurel blanco(Cordia alliodora), laurel negro(Cordia megalantha), caoba (Swietenia macrophylla), cedro (Cedrela odorata) y melina (Gmelina arbórea); cada árbol fue georreferenciado utilizando coordenadas UTM Datum WGS 1984 Zona 17M. La cantidad de semillas que pueden producir dichas especies forestales es proyectada por año la cual servirá como referencia para establecer programas de reforestación con materiales propios y adaptados a las condiciones ambientales en la provincia de Santa Elena Abstract  The study of selection of seed trees was carried out in the Olón, Dos Mangas and Salanguillo communes of the canton Santa Elena, Santa Elena province, Ecuador. The objective of the study was to identify, characterize and select seedlings of timber species with good morphological characteristics, and to allow seeds to be used for the propagation of forest species in nurseries for reforestation purposes. The study began with the identification and location of forest plantations of several forest species established between 2000 and 2005, on the plantations, the dasometric and morphological characteristics were evaluated, allowing the selection of 11 trees with desirable morphological characteristics corresponding to five forest species White laurel (Cordia alliodora), black laurel (Cordia megalantha), mahogany (Swietenia macrophylla), cedar (Cedrela odorata) and melina (Gmelina arborea); Each tree was georeferenced using coordinates UTM Datum WGS 1984 Zone 17M. The number of seeds that can produce these forest species is projected per year which will serve as a reference to establish reforestation programs with their own materials and adapted to the environmental conditions in the province of Santa Elena.

scholarly journals CROWN MORPHOMETRY FOR TWO VALUABLE TIMBER SPECIES FROM MIOMBO WOODLAND IN MOZAMBIQUE

Nativa ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 218-326
Author(s):  
Noé dos Santos Ananias Hofiço Hofiço ◽  
Emanuel Arnoni Costa ◽  
Frederico Dimas Fleig ◽  
César Augusto Guimarães Finger
Keyword(s):  
Prediction Models ◽  
Timber Species ◽  
Natural Forests ◽  
Miombo Woodland ◽  
Crown Length ◽  
Pterocarpus Angolensis ◽  
Hardwood Species ◽  
Morphometric Features ◽  
Height Increase ◽  
Individual Trees

Pterocarpus angolensis DC and Bobgunnia madagascariensis (Desv.) J. H. Kirkbr. & Wiersema are two hardwood species found in Miombo woodland. Crown size, being closely related to the photosynthetic capacity of a tree, is an important parameter in studies of the growth of individual trees. In this sense, the present study aimed to study the morphometric relationships of P. angolensis and B. madagascariensis as a resource to describe the morphometric features of these species. Data were sampled in 60 rectangular plots of 20 x 50 m, systematically distributed within the forest. In each plot, the diameter at breast height (DBH), height (h), crown insertion point (cih) and four crown radii of all trees with DBH ≥ 10 cm were measured. Results indicated that crown diameter and crown length of P. angolensis grow as DBH and height increase, the larger the crown, the greater the trees dimensions; as for B. madagascariensis, crown features have shown low correlation when considering DBH. It was concluded that crown features influence on tree growth and are important measures of description and planning of silvicultural activities to be performed in natural forests. The results are of interest to forest managers since they make decisions about silvicultural operations. Keywords: crown dimensions; prediction models; umbila; pau-ferro; forest management.

scholarly journals Influence of Dispersing Method on the Quality of Nano-Admixtures Homogenization in Cement Matrix

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4865
Author(s):  
Elżbieta Horszczaruk ◽  
Paweł Łukowski ◽  
Cyprian Seul
Keyword(s):  
High Speed ◽  
Mechanical Performance ◽  
Chemical Properties ◽  
Cement Composite ◽  
Cement Matrix ◽  
Cement Composites ◽  
Nano Sio2 ◽  
Mechanical Stirring ◽  
Physico Chemical ◽  
Nano Fe3o4

In recent years, a nano-modification of the cement composites allowed to develop a number of new materials. The use of even small amount of nano-admixture makes possible not only to improve the physico-mechanical properties of the cement materials, but also to obtain the composite with high usability, optimised for the given application. The basic problem of nano-modification of the cement composites remains the effectiveness of dispersing the nanomaterials inside the cement matrix. This paper deals with the effect of the type and size of the nanoparticles on the tendency to their agglomeration in the cement matrix. The main techniques and methods of dispersing the nanomaterials are presented. It has been demonstrated, on the basis of the results of testing of three nanomodifiers of 0D type (nano-SiO2, nano-Fe3O4 and nano-Pb3O4), how the structure and properties of the nanomaterial affect the behaviour of the particles when dissolving in the mixing water and applying a superplasticiser. The nanoparticles had similar size of about 100 nm but different physico-chemical properties. The methods of dispersing covered the use of high-speed mechanical stirring and ultrasonication. The influence of the method of nano-modifier dispersing on the mechanical performance of the cement composite has been presented on the basis of the results of testing the cement mortars modified with 3% admixture of nano-SiO2.

Microstructure–stiffness relationships of ten European and tropical hardwood species

2012 ◽  
Vol 177 (2) ◽  
pp. 532-542 ◽  
Author(s):  
Karin de Borst ◽  
Thomas K. Bader ◽  
Christoph Wikete
Keyword(s):  
Tropical Hardwood ◽  
Hardwood Species
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