Evaluating Thermal Performance and Environmental Impact of Compressed Earth Blocks with Cocos and Canarium Aggregates: A Study in Douala, Cameroon

peer reviewedA novel low-cost earthen construction system integrating biosourced aggregates is proposed for houses’ erection of low-income households. This study is based on in-situ measurements on two representative test cells constructed in Douala, with a typical hot and humid climate. One of these buildings is made with a hollow cement block as a reference, and the other with biosourced earth bricks modified with Cocos nucifera and Canarium schweinfurthii aggregates. Dynamic thermal simulations of the two test cells were performed using the EnergyPlus building performance simulation program. The results are based on measuring air temperature and humidity, and the simulation leads to defining the discomfort hours and the annual energy consumption. The adaptive ASHRAE 55 thermal comfort model was used to evaluate the comfort conditions. The results show that air conditioning systems provide the best comfort systems with minimums of about 95% for plastered and unplastered wall construction systems. Biosourced compressed earth brick constructions offered the best thermal performance with comfort ranges of around 96% and 44% for air conditioning and natural ventilation, respectively. In terms of energy consumed, there was a gain of about 100 kWh over the year. Energy consumption is lower in the biosourced compressed earth brick building than in the hollowed cement block building: this one offered the lowest comfort range of about 40% in natural ventilation. The construction provisions were considered for the life cycle assessment, and two scenarios describing the origin of the cement raw materials were considered. It can be seen that cement accounts for more than 95% of the impacts for both construction systems, as well as for the scenarios of its origin. In all situations, the hollowed cement block construction presented the highest impact on the global warming potential: 66 KgCO2eq and 89 KgCO2eq, respectively, without plaster and with plaster. It can also be seen that the plastered layer had a carbon footprint (in terms of Green House Gas Emissions (GHG emissions)) of almost 40% on the overall functional unit. Canarium Schweinfurthii and Cocos Nucifera materials accounted for only 1% of the overall impact

Formulation of biosourced compressed earth bricks with aggregate loads of Canarium schweinfurthii and Cocos nucifera

L’une des principales performances du matériau terre, est la régulation thermique. Afin de proposer à la population du Littoral camerounais un matériau à impact polluant réduit et avec lequel le confort thermique des habitacles serait évolué, nous nous sommes attelés dans cet étude à évaluer la possibilité d’utiliser la terre du Littoral camerounais pour l’élaboration des Briques de terre comprimées et stabilisées d’une part chimiquement de chaux et d’autre part mécaniquement par des granulats de Canarium schweintfurthii et Cocos nucifera. Ces agrégats biologiques ont démontré une forte influence sur les performances physiques, mécaniques et thermiques des BTCS obtenues. Les résultats valident la difficulté à utiliser la terre de la région du Littoral Camerounais pour les BTC avec une granulométrie bien que contenue dans le fuseau CRAterre présente une forme discontinue avec plateau. De même avons-nous des données de consistance assez faibles. En sélectionnant le stabilisant chaux, nous avons amélioré la cohésion de la terre et les BTCS obtenues bien que portées à maturation par vapeur, présentent des performances exploitables pour le domaine des combles, mais lesdites performances à améliorer pour des projets de construction haute performance et durable.Elaboration et caractérisation chimique physico-thermo-mécanique des briques de terre stabilisées/comprimées à charges de noyaux de Canarium schweinfurthii et Coco nucifer

Hydromechanical behaviour of BTCs with Canarium schweinfurthii and Cocos nucifera aggregates: sustainability analysis

Ce travail s’intéresse à l’impact de l’humidité sur le comportement mécanique du matériau terre dans son ensemble. Les matériaux testés sont à base de la terre de la ville de Douala dans la région du littoral-Cameroun. Des granulats de Canarium schweinfurthii (CS) et Cocos nucifera (CN) sont utilisés comme charges et un ciment comme stabilisant. Les échantillons parallélépipédiques de 220x95x45 mm3 sont réalisés à une presse hydraulique manuelle à la pression de compactage de 10 MPa. Quatre solutions aqueuses salines (KOH, NaCl, K2SO4, Na2Cr2O7) ont permis de conditionner les briques dans des bacs adiabatiques pendant 24 heures après différents jours de maturation (7, 14 et 28) jours. Les essais mécaniques de flexion 3-points et compression simple sont réalisés sur les échantillons conditionnés. Il en ressort que le comportement hydromécanique des BTC avec granulats de CS et CN suit un modèle linéaire pour les plages d’humidité relative obtenues

Effect of the Addition of Oil Palm Mesocarp Fibers on the Physical and Mechanical Properties of a Polyester Matrix Composite

This work focuses on the assessment of oil palm mesocarp fibers as reinforcement in a composite material with an unsaturated polyester matrix. Several volume ratios of OPMF reinforcement (0 to 15%) were used, the fibers being distributed randomly. The resulting composite was characterized on the physical and mechanical aspects. Physically, the true and apparent densities were determined as well as the porosity rate. It appears that the addition of fibers further lightens the composite and increases the porosity. The water absorption rate of the different composites samples was evaluated. The more fibers the composite contains, the higher its water absorption rate. On the mechanical aspect, the bending modulus of elasticity, bending stress at break, and breaking strain were evaluated through a three-point bending test on all combinations. The same parameters were also evaluated for certain combinations by a unidirectional tensile test. It appears from this mechanical characterization that the volume fraction of 5% reinforcement has the highest specific modulus. Impact tests were performed on samples of this combination using several sizes of reinforcing fibers. Impact resistance is enhanced as the size of the inclusion increases. The Halpin-Tsai micromechanical model for randomly distributed short fiber composites was used for the inverse approach determination of the theoretical moduli of the matrix and OPMF, then in a direct approach to determine the elastic modulus of the composite at 7.5% reinforcement

Investigation of the Physical and Mechanical Properties of Raffia Vinifera Fibers along the Stem

The study of the physical and mechanical properties of raffia vinifera fibers along the stem is examined in this work. In central Africa, these fibers are already being used by craftsmen in the field of textile and decoration. The cross-section of fibers is higher at the base of the stem and grows from the periphery toward the center on a transverse position. By the Archimedes method, the obtained bulk density was between 0.1288 g/cm3 and 0.2368 g/cm3 and in a transverse position, it increases from the center toward the periphery. The dynamic tensile tests were used to estimate the Young’s modulus that lies among 0.88 GPa and 7.9 GPa and the low values are at the base of the stem. The specific Young’s modulus was deduced and varied from 7.33 GPa/(g/cm3) and 66.00 GPa/(g/cm3). Finally, through the strain, the microfibril angle was found and it is oscillated from 29.81° to 48.65°

Development and characterization of agglomerated abrasives based on agro-industrial by-products

The present work deals with the valorization of agro-industrial by-products to realize bonded abrasives. Four by-products were studied because of their wide availability and mechanical properties: palm nuts shells (Elaeis guineensis), Coco Nucifera shells, fruit kernels of Canarium schweinfurthii and fruit kernels of Raffia Vinifera. The Oliver and Pharr hardness and Young’s modulus of the raffia cores are obtained by instrumented macro indentation, giving the values 101 MPa and 1.82 GPa, respectively. The development of the abrasive wheels was based on the experimental method of full factorial design at 2 levels. Porosity, hardness, resilience, material removal rate and wear were determined. Leeb 280 HL hardness shoe sole material was used for tribological testing. The optimal formulations have 20% binder content and 1 mm grain size of the four agro-industrial by-products used with a higher material removal rate and a longer life than commercial grinding wheels. These results presage their use in the shoe industry and abrasive disc huskers

Influence of temperature on the creep behaviour by macroindentation of Cocos nucifera shells and Canarium schweinfurthii cores (bio-shellnut wastes in Cameroon)

The aim of this study was to show how temperature modifies the mechanical characteristics of the Cocos nucifera (CN) shells and the Canarium schweinfurthii (CS) cores. The test consisted in performing an instrumented macroindentation on prismatic specimens in an adiabatic chamber; the indentation carried out according to four temperature ranges (30 °C, 50 °C, 70 °C, 90 °C). The Oliver and Pharr method is used for the analysis of mechanical parameters in indentation: reduced Young's modulus, hardness, creep coefficient. These parameters have enabled to estimate indirect characteristics such as toughness and ultimate mechanical stress to be obtained. The creep data are simulated to have the rheological model to these materials by considering the statistical criteria. As a global observation, when the temperature increases, the mechanical parameters decrease; although CN is more sensitive to the temperature gradient than CS, these 2 materials show performances that allow them to be classified as engineering polymer materials according to the Ashby diagram

Physical, Water Diffusion and Micro-Structural Analysis of “Canarium Schweinfurthii Engl”

peer reviewedThe purpose of this study is to determine the morphological, microstructural characteristics and water diffusion parameters of the Canarium schweinfurthii (CS) shellnut. This work is part of a vast project to valorize the above-mentioned cores for possible industrial use as charges in composites or abrasives materials. The study was based on the characterization of intrinsic physical characteristics of the coreshells scanning electron microscopic (SEM) observations desorption, adsorption and absorption kinetics. The water diffusion phenomenon was modeled and it appears that the Page model well predicted the kinetic of drying, absorption and adsorption. The effective diffusion coefficient and the energy of activation were calculated at three isothermal temperatures (50˚C, 70˚C and 90˚C). There was a tendency for hysteresis in the sorption-desorption cycles. These results strongly predicted the possibility of using these products as a filler in composites, clay building materials and cement because of their high water diffusion stability on a macroscopic scale