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Identification of the Diffusion Coefficients of Pollutants ( N O 3 - and Mn2+) through the Walls of Concrete Tank and Vulnerability of the Stored Water Quality

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Engineering（科研） 2024年第9期16卷 246-274页

作者： narcisse malanda Bienvenu Ebata Ndion Christian Tathy Thibault Mongo Paul Louzolokimbembe Nation School Superior Polytechnic Marien Ngouabi University Brazzaville Republic of Congo Superior Institute Architecture Town Planning Building and Public Works University of Dnis Sassou Nguesso Kintl Republic of Congo

The populations of urban centers in Congo-Brazzaville have decided to develop various methods of water storage (concrete or masonry underground tanks) for domestic use, due to shortages in the distribution of water through the public network. However, questions remain as to the physico-chemical quality of the water stored in these tanks, when these structures are built in wet and relatively polluted areas. This paper presents a model of pollutant diffusion through the cementitious matrix (concrete) of tank walls simulated at a buried reservoir. The results of the experimental and numerical simulations show that certain concrete parameters, such as porosity, permeability and diffusivity, have a significant influence on the transfer of pollutants through the concrete walls, thus altering the physico-chemical quality of the stored water. The numerical models (1D) used to predict pollutant transfer and the quality of the stored water are consistent with those of the optimal control for identifying the diffusion coefficient. Major ion concentrations appear to be correlated with system porosity and diffusion coefficient. Nevertheless, the identification of the diffusion coefficient from the optimal control method, based on an explicit numerical resolution of a finite volume PDE for the approximation of the experiment, is not consistent with that of the optimal control method.

关键词： Buried Tank Water Concrete Modelling Optimal Control Diffusion Coefficient

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Comparative Analysis of Statistical Thickness Models for the Determination of the External Specific Surface and the Surface of the Micropores of Materials: The Case of a Clay Concrete Stabilized Using Sugar Cane Molasses

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Geomaterials 2024年第2期14卷 13-28页

作者： Nice Mfoutou Ngouallat narcisse malanda Christ Ariel Ceti malanda Kris Berjovie Maniongui Erman Eloge Nzaba Madila Paul Louzolo-Kimbembe Mechanics Energy and Engineering Laboratory Higher National Polytechnic School Marien Ngouabi University Brazzaville Republic of the Congo National Institute for Research in Engineering Sciences Innovation and Technology (INRSIIT) Brazzaville Republic of the Congo Higher Institute of Architecture Building Planning and Public Works Denis SASSOU N&#8217GUESSO University Kint&#233l&#233 Republic of the Congo Hydrogen Research Institute University of Quebec in Trois Rivieres Quebec Canada Superior Normal School (ENS) Marien Ngouabi University Brazzaville Republic of the Congo

In this work, four empirical models of statistical thickness, namely the models of Harkins and Jura, Hasley, Carbon Black and Jaroniec, were compared in order to determine the textural properties (external surface and surface of micropores) of a clay concrete without molasses and clay concretes stabilized with 8%, 12% and 16% molasses. The results obtained show that Hasley’s model can be used to obtain the external surfaces. However, it does not allow the surface of the micropores to be obtained, and is not suitable for the case of simple clay concrete (without molasses) and for clay concretes stabilized with molasses. The Carbon Black, Jaroniec and Harkins and Jura models can be used for clay concrete and stabilized clay concrete. However, the Carbon Black model is the most relevant for clay concrete and the Harkins and Jura model is for molasses-stabilized clay concrete. These last two models augur well for future research.

关键词： Statistical Thickness Model External Specific Surface Microporous Surface Clay Concrete Molasses

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Comparative Analysis of Statistical Thickness Models for the Determination of the External Specific Surface and the Surface of the Micropores of Materials:The Case of a Clay Concrete Stabilized Using Sugar Cane Molasses

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Geomaterials（地质材料） 2024年第2期 13页

作者： Nice Mfoutou Ngouallat narcisse malanda Christ Ariel Ceti malanda Kris Berjovie Maniongui Erman Eloge Nzaba Madila Paul Louzolo-Kimbembe

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Survey on Storage of Water for Domestic Use in Underground Reinforced Concrete Tanks: The Case of Brazzaville (Republic of Congo)

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Open Journal of Civil Engineering 2014年第1期4卷 13-22页

作者： narcisse malanda Paul Louzolo-Kimbembe Laboratory of Civil Engineering and Environmental Engineering National School of Engineering University Marien Ngouabi Brazzaville Congo

The problem of water supply from the public distribution network still poses very serious problems in many cities in developing countries. Intermittent water supply pushes some households to build underground reinforced concrete tanks for water storage to cope with unwanted water breaks. This study that relies on the results of a survey of households in some areas of the city of Brazzaville (Republic of Congo) aims to verify the importance that users attach to the quality of the works constructed. Indeed, the reliability of the tanks resulting in their impermeability to the external environment has a direct impact on the quality of stored water and therefore the use that is made of water daily. Five areas were selected because of their soil moisture. By 256 tanks identified, 143 are made of reinforced concrete and 113 in masonry. The coating materials used to seal the walls are preferably the earthenware tiles (64% of tanks), then the Sika cement (31%). Food painting (5%) is only rarely used. However, 66% of households are not assured of the potability of the water stored. A significant number of households (46%) think that the stored water could be contaminated with noxious substances seeping from the outside through the walls of the tanks. The issue of sealing of underground water tanks, especially in areas where the water table is shallow, seems concerned users.

关键词： Underground Tanks Watertightness Reinforced Concrete Water Storage Potability Household

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Microstructure of Fine Clay Soils Stabilized with Sugarcane Molasses

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Open Journal of Civil Engineering 2022年第2期12卷 247-269页

作者： narcisse malanda Nice Ngouallat Mfoutou Erman Eloge Nzaba Madila Paul Louzolo-Kimbembe National Upper Polytechnic School Marien Ngouabi University Brazzaville Republic of Congo Department of Chemistry Biochemistry and Physics and Hydrogen Research Institute University of Quebec in Trois-Rivières Trois-Rivières Canada National Upper Education School Marien Ngouabi University Brazzaville Republic of Congo

Sugar cane molasses has proved cohesive and excellent performance on soil aggregates (fine particles). However, the microstructure of consolidated soil by the molasses is not yet subjected to research. The analysis results of sample without molasses (0%) and consolidated samples at 8%, 12%, and 16% show that the molasses acts on the structure of clayey fine soil developing its microstructure of airy matrix type (sample without molasses (0%) to a microstructure of a qualified type, more solid. Consolidated samples to 8%, 12%, 16% of molasses). We also observe the presence of inter-aggregate pores (mesopores) of similar size in all samples. The results of porosimetrical analyses (BJH) of the sample without molasses and consolidated samples to 8%, 12%, and 16% show that simultaneous porous volumes of samples are reduced with the increasing of molasses quantity. This latter, therefore, acts on the porous volume (micropore 2 nm and mesopore 9 nm) by reducing them which really means, molasses occupies the porous volume of the sample. However, this sample seems not to have any effect on the size of mesopores 9 nm. Thus, this product induces the evolution of the soil structure towards the highly dense and condensed structure. Consequently, materials in consolidated soil by molasses will have mechanical properties far superior to those of materials consolidated soil without molasses.

关键词： Microstructure Consolidated Clayey Fine Soil Molasses of Sugar Cane Mesopore Micropore Specific Surface Area

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Effect of Wood Waste on Acoustic and Magnetic Properties of Composite Bricks and Correlation between Sound Velocity and Magnetic Induction in These Bricks

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Open Journal of Composite Materials 2020年第1期10卷 15-25页

作者： Gilbert Ganga Adolphe Kimbonguila Manounou narcisse malanda Michel Dzondo Gadet Timothée Nsongo National Advanced School of Engineering University Marien Ngouabi Brazzaville Congo Center for Research and Initiation of Technology Projects (CRIPT) Brazzaville Congo Laboratory of Mechanics Energtics and Engineering ENSP-UMNG Brazzaville Congo Facultyof Sciences and Technology University Marien Ngouabi Brazzaville Congo Center of Géological and Mining Research Brazzaville Congo

In the present study, kambala (botanical name: Chlorophora excelsa and Chlorophora regia) wood wastes were incorporated into stabilized earth bricks in order to test their acoustic insulation capacity of the walls;leading to better waste management from the timber industry. Two methods have been applied to determine the influence of the wood waste content in the stabilized earth bricks, on the weakening of the level of noise reception coming from the environmental medium, in an apartment built with composite bricks (earth + wood chips + cement). This influence has also been analyzed on the magnetic field induced by these bricks. The results showed that the level of sound reception through these bricks decreases with increasing wood waste content regardless of the method used (from 110 dB to 68 dB, respectively for Φb = 0% and Φb = 8%). The kambala wood waste in cement-stabilized clay bricks induces a magnetic field that increases with the wood waste content;the high contents of the wood chips causing an increase in the magnetic permeability of the composite medium. The correlation between the noise level and the magnetic field of the bricks shows that the noise level declines with increasing magnetic induction of the bricks.

关键词： Kambala Tree Wood Waste Clay Brick Sound Velocity Magnetic Field

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Thermo-Mechanical Properties Study of Stabilized Soil Bricks to Sugar Cane Molasses and Cassava Starch Binders

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Open Journal of Applied Sciences 2023年第2期13卷 240-260页

作者： narcisse malanda Jean Albin Nkaya Gilbert Ganga Ngambara Emamou Nondel Durvy Paul Louzolo-Kimbémbé Polytechnic National Superior School (ENSP) Marien Ngouabi University Brazzaville Republic of the Congo Superior Normal School (ENS) Marien Ngouabi University Brazzaville Republic of the Congo National Institute for Research in Engineering Sciences Innovation and Technology (INRSIIT) Brazzaville Republic of the Congo

The current study deals Swith thermo-mechanical properties of stabilized soil small bricks with the help of organic binders of sugar cane molasses and cassava starch. Different formulations of soil concrete have been suggested after the geotechnical characterization of samples of soil was taken. From these, it arises that the studied soil is the most plastically clay (of type A3) according to GTR classification. Samples made of small bricks and measured out at 4%, 6% and 8% of binders (molasses, starch or molasses + starch) have been warmed up to different temperatures (100°C, 150°C, 200°C and 250°C) for the rising of the thermic behavior under different conditions and submitted to crushing testings for the estimation of characteristic resistances to the compression. According to the mechanical behavior, we note an improvement of resistances for small bricks measured 4%, 6% and 8%, of molasses respectively of 32.44%, 32.06% and 23.43% against the value of reference for small bricks without molasses. In the same way, the binder (molasses + starch) also reveals an improvement of resistance to the compression of 13.27%, 26.17% and 26.17%. On the contrary, the stabilization with the starch binder did not bring a significative improvement. According to the thermic influence, the heating at 100°C of stabilized small bricks at 4%, 6% and 8% of molasses, reveals a significative improvement of resistances. Moreover, the stabilization with the starch reveals on the contrary a good behavior for heatings at 150°C and 250°C. In short, for the binder (molasses + starch), it is the heating at 200°C that shows some improvements of remarkable resistances. Different analyses of realized statistics also show the effectivity of obtained results. For all realized formulations, the measuring out at 6% of binders (molasses, or molasses + starch) seems as optimal in front of the best thermo-mechanical revealed properties.

关键词： Clay Molasses Cassava Starch Heating Compressed Soil Brick Mechanical Resistance

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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

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Impact of pH Water and Mineralogical Microstructure of Soil Mixed with Wood Waste on the Compressive Strength of Composite Bricks;and Bricks Resistance Modeling

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Open Journal of Civil Engineering 2020年第1期10卷 9-21页

作者： Gilbert Ganga narcisse malanda Diogène Pongui Ngoma Timothée Nsongo Michel Dzondo Gadet National Advanced School of Engineering University Marien NGouabi Brazzaville Congo Center for Research and Initiation of Technology Projects (CRIPT) Brazzaville Congo Laboratory of Mechanics Energtics and Engineering ENSP-UMNG Brazzaville Congo Faculty of Science and Technology University Marien NGouabi Brazzaville Congo Centerof Géological and Mining Research (CRGM) Brazzaville Congo

This study includes the manufacture of cement stabilized clay bricks with embedded mahogany chips. The impact of this waste and its interaction with water in the bricks was evaluated on the mechanical properties. The compressive strength tests using a universal press were carried out on bricks with and without adding wood chips. The results obtained show that the incorporation of wood chips into the bricks decreases the compressive strength. This reduction in compressive strength led us to conduct an analysis of clay and water as intrinsic factors, before and after incorporation of untreated wood waste. Thus, a mineralogical analysis of the clay with and without mahogany chips was made using an X-ray diffractometer, using an anticathode of cobalt with the line Κα, of wavelength λ = 1789Å. After quantification of the mineral constituents, it is noted that the concentration of SiO2 decreases considerably in the clay with addition of wood chips, resulting in the reduction of the compressive strength in these composite materials (from Rc = 9.26 MPa at 0% of chips to 3.55 MPa at 8%). A mathematical model following the interpolations of Lagrange was then proposed. The analysis of the water resulting from the impregnation of dry wood chips in the water, shows that the water becomes strongly acid (pH = 4.3 at the 7th day of immersion), thus contributing to the reduction of resistance. This analysis of intrinsic factors will allow future studies to take into account the treatment of wood waste by different processes in order to increase the mechanical, thermal and acoustic properties of composite bricks with the same contents, thus generating massive support for the use of its composite materials.

关键词： Clay Bricks Mineralogical Analysis Wood Chips Compressive Strength pH Water

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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

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