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A Model of physico-mechanical Characterization of Sangaredi Bauxites and Related Rocks Taking into Account Their Litho-Genetic Type

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Journal of Minerals and Materials Characterization and Engineering 2024年第6期12卷 281-298页

作者： Oumar Keita Mory Diane Department of Hydrology University of Nzrkor Nzrkor Guinea Guinea Bauxite Company Kamsar Guinea

The Sangarédi bauxite deposit in the Republic of Guinea contains several bauxite types depending on their litho-genetics. For rational and sustainable exploitation, determining the physical and mechanical properties of these different bauxite types is essential for mining companies. This paper presents a model for the physico-mechanical characterization of Sangarédi bauxites according to their litho-genetic type. Eight pits were drilled, and samples were collected from different layers at different depth intervals for each bauxite type. Physical and mechanical characterization tests were then carried out on 27 samples to determine the following parameters: water of absorption (%), compressive strength (kgf/cm2) and dynamic tensile strength (kgf/cm2). The effect of depth of sampling on these physico-mechanical parameters was evaluated. An average value of the parameters was made for each bauxite type. The results showed that the physico-mechanical characteristics of bauxites depend on the depth of sample collection, and the average value of the parameters constitutes the representative values of the bauxite type. Finally, a comparative study of the average value of the physico-mechanical parameters of the different bauxite types was carried out.

关键词： Bauxites Litho-Genetics physico-mechanical Compressive Strength Dynamic Tensile Strength

Relationship between physico-mechanical Properties, Compacting Pressure and Mixing Proportion of Briquettes Produced from Maize Cobs and Sawdust

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Journal of Sustainable Bioenergy Systems 2014年第1期4卷 50-60页

作者： Stephen J. Mitchual Kwasi Frimpong-Mensah Nicholas A. Darkwa Department of Construction and Wood Technology Education University of Education Winneba Kumasi Campus Kumasi Ghana Department of Wood Science and Technology Kwame Nkrumah University of Science and Technology Kumasi Ghana

This study examined the relationship between selected physico-mechanical properties, compacting pressure and mixing proportion of briquettes produced from combination of maize cob particles and sawdust of low, medium and high density timber species. Particle sizes of maize cobs and sawdust used for the study were ≤1 mm. The two materials were combined at mixing percentages of 90:10, 70:30 and 50:50 (Sawdust:maize cobs). Briquettes were produced at room temperature (28°C) using compacting pressures 20, 30, 40 and 50 MPa. The results suggested that combining maize cob particles with sawdust of low, medium and high density wood species could significantly enhance the relaxed density, compressive strength in cleft and impact resistance index of briquettes produced from agricultural biomass residue like maize cobs. The results further indicated that the physical and mechanical characteristics of briquettes produced from combinations of sawdust of low density species and maize cobs were exceptionally higher than that produced from combinations of maize cob particles, and medium density and high density timber species. The R2 values for the regression model between the independent variables (mixing percentage and compacting pressure) and relaxed density, compressive strength in cleft and impact resistance index of briquettes produced from combinations of maize cob particles and sawdust of low density species (Ceiba pentandra) were 0.966, 0.932 and 0.710 respectively. This study provides a hope for briquetting maize cobs at room temperature using a low compacting pressure.

关键词： Briquette Compacting Pressure Maize Cobs Mixing Proportions physico-mechanical Properties Sawdust

STUDIES ON PHYSICAL AND mechanical PROPERTIES OF DAHURIAN LARCH-WOOD OF TWO WOOD COLOURS

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Journal of Northeast Forestry University 1994年第4期5卷 68-72页

作者：卓丽环王为众 1. Northeast Forestry University China

Dahurian larch growing in Daxing’an Mountains can be divided into two types according to the wood colour: one is red, the other is white. Based on the national standard of the "Testing methods for physical &mechanical properties of wood", the parameters of wood colour and physico-mechanical properties of the above two different woods were tested and *** result showed that the colour rational phenetic parameters, physico-mechanical properties and work abilities of thc two woods were quite different, combincd with the other morphological characteristics, they belong to intraspccific two different types of Dahurian larch. The white wood is superior to the red one as a valuable timber tree. Because the cocfficients of shrinkage, hardness and colour of both are different, they were mixed working in the past, inevitably there have been various defects in working. In order to overcome these defects, we propose that the departments of wood production, salesmen and consumers should use them differently according to their individual character.

关键词： Red wood White woods Dahurian larch Parameters of wood colour physico-mechanical properties

Elaboration and Characterization of a Fiber Composite Material Made of Petioles of the <i>Elaeis guineensis</i>(Oil Palm)

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Open Journal of Composite Materials 2020年第4期10卷 106-117页

作者： Ze Eric Parfait Tchotang Théodore Souck Joseph Loic Nfor Clins Wiryikfu Pondi Joseph Mpoung Léon Arnaud Local Materials Promotion Authority Yaoundé Cameroon National Advanced School of Engineering Yaoundé University of Yaoundé 1 Department of Mechanical Engineering Laboratory of Civil Engineering and Mechanics Yaoundé Cameroon

The aim of this study is to characterize physically and mechanically a polyester/fiber palm petiole composite material. This work made it possible to provide the local database of composite materials but also to develop agricultural waste. According to BSI 2782 standard three formulations [A (10% fiber, 90% polyester);B (20% fiber, 80% polyester) and C (30% fiber, 70% polyester)]. Water Absorption rate, density, compressive and three points bending tests are carried out on the samples obtained by the contact molding method for each formulation. The material composite obtained by adding fibers from palm oil petiole has a density of 17.98% lower than the one made of pure polyester. Fiber reinforcement rate has no impact on the density of the composite. Formulation A most absorbs water while formulation C has good tensile/compression characteristics and the greatest breaking stress in bending among the three formulations.

关键词： Elaboration Characterization physico-mechanical Composite Polyester Petioles Oil Palm

Influence of Aggregate Grain Size on the Formulation of Sand Concrete in the Construction Industry in Congo

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Geomaterials 2019年第4期9卷 81-96页

作者： Charlène Bassolokidi Nkengue Narcisse Malanda Gilbert Ganga Paul Louzolo-Kimbembe Guy Richard Mouengue National Higher Polytechnic School Marien Ngouabi University Brazzaville Congo Office of Control of Buildings and Public Works Brazzaville Congo

The main objective of this study is to contribute to the optimization of the formulation of sand concretes and its valorisation according to natural sands from different quarries or extraction sites. Physical characteristics of natural sands have been determined and improved by the addition of crushing sand, taking into account the too fine elements of the sand. Four types of sand were used (Congo River, Djiri, Mfilou, crushed sand). The concrete formulations proposed from improved sands (30% crushed sand and 70% natural sand) reveal an increase in mechanical strength. Thus, it appeared that this improvement of the natural fine sands by the crushing sand has brought a clear increase in the maneuverability of the concretes and the physico-mechanical characteristics of nearly 50%, although this crushing sand has a sand equivalent value of less than 70%. These results augur well for the durability of structures in the construction industry in Congo.

关键词： Sand Formulation Recovery Materials Sand Concrete physico-mechanical Characteristics Construction

The Reinforcing Effect of Graphene on the mechanical Properties of Carbon-Epoxy Composites

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Open Journal of Composite Materials 2020年第2期10卷 27-44页

作者： Hadimani Shivakumar N. M. Renukappa K. N. Shivakumar B. Suresha Department of Electronics and Communication Engineering Kalpataru Institute of Technology (Visvesvaraya Technological University Belagavi) Tiptur Karnataka India Department of Electronics and Communication Engineering JSS Science and Technology University Mysuru Karnataka India Centers for Composite Materials Research North Carolina A & T State University Greensboro NC USA Center for Composite Materials Research The National Institute of Engineering Mysuru India

Graphene nanoplatelets (GNPs) are novel nanofillers holding attractive characteristics, including vigorous compatibility with majority polymers, outstanding mechanical, thermal, and electrical properties. In this study, the outstanding GNPs filler was reinforced to the epoxy matrix and carbon fabric/epoxy hybrid composite slabs to enrich their mechanical properties. Graphene nanoplatelets of 0.5, 1, 1.5 and 2 weight percentages were integrated into the epoxy and the physico-mechanical (microstructure, density, tensile, flexural and impact strength) properties were investigated. Furthermore, the mechanical properties of unfilled and 1 wt% GNPs filled carbon fabric/epoxy hybrid composite slabs were investigated. Subsequently, noteworthy improvement in the mechanical properties was conquered for the carbon fabric/epoxy hybrid composites.

关键词： Graphene Nanoplatelets Carbon Fabric/Epoxy Hybrid Composite physico-mechanical Properties Impact Strength

Concrete Formulation Study for Informal and Semi-Informal Construction Sectors

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Open Journal of Civil Engineering 2019年第1期9卷 57-79页

作者： Narcisse Malanda Paul Louzolo-Kimbembe Louis Ahouet Jarlon Brunel Makela Guy-Richard Mouengue National Polytechnic High School Marien Ngouabi University Brazzaville Congo Normal High School Marien Ngouabi University Brazzaville Congo Building and Public Works Control Office Brazzaville Congo

The present work consisted in carrying out a study on the effective formulation of concrete for an optimal resistance to compression (fc28) between 20 and 30 MPa for the sites animated by the actors of the informal and semi-informal sectors of the construction. Studies have been carried out on projects under construction, by taking samples of fresh concrete in order to evaluate their real compressive strengths. These surveys show that there is a problem in the concrete formulation, as nearly 2/3 of the results show the lack of technical knowledge on concrete formulation practices. Indeed, on eight sites surveyed and whose fresh concrete samples were taken, only two sites (7 and 8) report fairly consistent results. Their 28-day compressive strength values are respectively 35.36 and 22.18 MPa. In addition, various formulations proposed with aggregates from different quarries or extracts from the bed of the Congo River, were determined in the laboratory. This study allowed us to obtain fairly objective results overall, which is characteristic of concretes of required quality. Of the six (06) formulation proposals, average resistances of 19.6 MPa at 07 days and 25.28 MPa at 28 days were obtained. These results at 28 days are in the range of 20 to 30 MPa, set as objective in this study. These formulations can be a reliable source for concrete manufacturers in these construction sectors. Similarly, the statistical study based on principal component factor analysis tests has shown that the most appropriate formulation, in terms of mechanical resistance, is that proposed with sand extracted from the Congo River (formulation 3). This is justified by the fact that this sand is consistent and has a good granular distribution.

关键词： Formulation Concretes Aggregates Cement physico-mechanical Characteristics Informal and Semi-Formal Sectors

Technological Evolution of Historic Structural Mortars

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Journal of Civil Engineering and Architecture 2014年第7期8卷 846-854页

作者： Vasiliki Pachta Maria Stefanidou Stavroula Konopisi Ioanna Papayianni Department of Civil Engineering Aristotle University of Thessaloniki Thessaloniki 54124 Greece

Mortars are among the first building materials used in constructions, even from prehistoric times （8th millennium BC）. Their study reveals a great source of information regarding the evolution of their technological characteristics and application techniques, the availability and exploitation of raw materials, as well the wider socio-economic aspects of each era. The aim of this paper is to comparatively evaluate the analysis results from approximately 1,000 structural mortar samples taken from various monuments and historic buildings of Greece, dated from the Hellenistic period, until the beginning of the 20th century. The analysis focused in the determination of their physico-mechanical and chemical properties, such as porosity, apparent specific gravity, mechanical strength, aggregates type and granulometry and chemical composition. Through the results＇ evaluation, significant remarks can be made upon the evolution of the raw materials used （binding system, aggregates, additives）, as well as regarding the final properties of historic structural mortars. It is concluded that hydrated lime was the main binding agent used for a long-lasting period of 2.5 millenniums, while mixed type binding systems based on lime and natural pozzolan were systematically used for producing durable mortars, resistant to humidity. In any case, it seems that ancient masons were fully aware of the significant role of mortars in constructions and were capable of exploiting the available raw materials and application techniques to the maximum.

关键词： Structural mortars technological evolution physico-mechanical chemical properties.