Search

This study specifically investigated the influence of the composition of aluminosilicate material i.e. the substitution of metakaolin by rice husk ash and the nature of alkaline activators (Na+/K+) on mineralogical, structural, physical and mechanical properties of geopolymer binders. This influence was evaluated based on X-ray diffraction (XRD), Fourier Transform InfraRed spectroscopy (FTIR) and Scanning Electron Microscope (SEM analyses, apparent density, water accessible porosity, compressive strength and thermal properties. Two types of geopolymer binder were synthesized according to the type of alkali activator used, the NaOH-based geopolymer and the KOH-based geopolymer. The results of characterization performed after 14 days of curing of geopolymer samples showed that the activation of the aluminosilicate powder using alkaline solution led to change in their microstructure. The highest compressive strength was obtained with the NaOH-based geopolymer.

Oil Palm Shell (OPS) concrete can be used in different fields of construction. To determine more accurately the fields of application, it is important to know and understand the behaviour of OPS concrete over the long term and when it is in aggressive environments. This paper presents the results of studies conducted on the durability of OPS concrete. Water absorption capacity, electrical resistivity and apparent diffusion of chloride ions have been measured on different concrete samples. In addition, the behaviour of OPS concretes to carbonation was studied in an environment rich in carbon dioxide. Results show that OPS concrete has an absorptivity of 0.97 kg/m2·h1/2, an electrical resistivity of 64.37 Ω·m and an apparent diffusion coefficient of chloride ions of 3.84 × 10-12 m2/s after 90 days. All these results of OPS concrete are very close to those of concrete with normal aggregate and other lightweight concrete, which mean OPS concretes have globally good properties with regard to durability.

International audience; This study is focused on the use of coal bottom ash from Tefereyre (Niger) power plant coal-fuelled, as a fine aggregate in cementitious mortar. Various volume fractions of natural sand (0%, 10%, 20%, 30%, 40%, 50%, 75%, and 100%) were replaced by the same volume of fine aggregates of coal bottom ash. In order to determine the effect of coal bottom ash incorporation on the composites obtained, fresh and dry density water absorption, porosity, thermal conductivity, ultrasonic pulse velocity, gas permeability and microstructure analyses were investigated. The results show that incorporating coal bottom ash in mortar causes an increase in the apparent porosity and that leads to an increase of the water absorption and the apparent permeability of the samples at 28 days curing age. The densification of bottom ash mortar during the curing age contributed to significantly reduce the increase in the porosity and the apparent permeability. This densification was confirmed by SEM analysis and ultrasonic velocity measurement. However, the use of coal bottom ash reduces the specific weight and the thermal conductivity of cementitious materials. Overall, the mortars containing coal bottom ash offer an opportunity to recycle (by-product) wastes. © 2016 Elsevier Ltd

cited By 10; International audience; Geopolymer binders constitute an environmental friendly alternative of Portland cement, wellknown for its contribution to the emission of greenhouse gases. In this article, we study the possibility of valorizing local materials in Burkina Faso, namely metakaolin and rice husk ash, in geopolymer binders synthesis using sodium hydroxide solution. The study focused on the influence of the addition of rice husk ash and the curing temperature on the mineralogical, microstructural, physical and mechanical properties of geopolymer binders, through X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, weight loss, apparent density, porosity accessible to water and compressive strength. Three types of geopolymer binders were synthesized in this study: geopolymer binders based on metakaolin alone (AN) and two other binders containing 5% (BN) and 10% (CN) of rice husk ash respectively. The results obtained show the formation of new mineral phases and an improvement of the mechanical strength with the addition of rice husk ash and with curing temperature. There is also a high porosity for all synthesized geopolymer binders. These results are presented and discussed in terms of SiO2/Al2O3 ratio and degree of polymerization. © 2016 Elsevier Ltd

International audience; This research work focuses on the study of the durability of composite cements based on coal bottom ash powder produced by SONICHAR in Niger. After a physicochemical and environmental characterization of the coal bottom ash powder, mortar test specimens were made. In these specimens, 10%, 15% and 20% of cement were replaced by identical mass percentages of coal bottom ash powder. Durability studies focused on the determination of the chloride ions apparent diffusion coefficient, the measurement of the depth of carbonation and the accelerated ammonium nitrate leaching. The influence of carbonation and leaching were examined using the following parameters: pore distribution, gas permeability, porosity accessible to water, capillary absorption and electrical resistivity. The results show that the incorporation of coal bottom ash powder into CEM I leads to an increase in the depth of carbonation. This increase is more significant when the substitution rate exceeds 10%. In the leaching test, the partial substitution of coal bottom ash powder in CEM I up to 20% does not significantly affect the durability parameters of the composites compared to the control mortar. Diffusion test shows that for mortars containing less than 15% substitution, there is no significant influence on the chloride diffusion coefficient. A slight decrease is observed for mortar containing 20% substitution. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.

International audience; The overuse of natural aggregates for construction causes many environmental problems. In light of their environmental impact, the discussion has increasingly focused on using alternative plant-based materials and processes such as oil palm shells (OPS). However, previous studies show that OPS have a weak adhesion with cement paste, which results in a decrease in the physical and mechanical properties of OPS concretes. One of the solutions for this problem is to carry out a surface treatment on OPS before using them in concrete. This study has examined the influence of five treatments on the physical and mechanical properties of concrete: treatment with lime (CH), sodium silicate (SS), polyvinyl alcohol (PVA), heat treatment (TH) and OPS saturation (SAT). Lime treatment (CH) on OPS showed good improvement in the mechanical properties of concrete, compared to untreated OPS. © 2017 Elsevier Ltd

International audience; The main objective of this study is to evaluate the feasibility of stabilizing compressed earth blocks with a geopolymer binder that is less polluting than Portland cement. Thus, a performance evaluation of these materials compared to non-stabilized or Portland cement-stabilized earth blocks was the main aim this study. The geopolymer was synthesized from a mixture of metakaolin and sodium hydroxide solution. Laterite formed the principal matrix of the bricks. Compressed Earth Bricks (CEBs) stabilized with 5, 10, 15 and 20% of geopolymer were produced and compared to both CEBs containing 8% of Portland cement and CEBs without stabilizer. After a cure of 14 days for the specimens without stabilizer and geopolymerized CEBs and 21 days for Portland cement-stabilized CEBs, the blocks were subjected to several characterization tests in order to evaluate their properties (physical mechanical and thermal properties). The results showed that geopolymerization of CEBs significantly improved their mechanical performance and gave them thermal properties that were very similar to those of non-stabilized blocks. For a 15% geopolymer content, these materials displayed properties comparable to those of Portland cement-stabilized CEBs, in particular with regard to their stability in water. (C) 2018 Elsevier Ltd. All rights reserved.

Oil palm shell is an interesting organic material that can be used as aggregate for concrete. It can help mitigate the environmental problems caused by the concrete industry. We intend to contribute to the knowledge of OPS (oil palm shells) concrete studying the physical mechanic and thermal behavior. Then, this paper presents the results of investigations carried out on the effects of replacing by volume, CGA (crushed granite aggregate) in concrete with OPS. Then, the dry density, apparent porosity, water absorption, electrical resistivity, thermal parameters, flexural strength, compressive strength and static elastic modulus are investigated. Microscopic analysis with an SEM (scanning electron microscopic) is also conducted. The results show that replacing crushed granite aggregate by OPS, increases the apparent porosity of concrete. This makes the concrete lighter and the concrete mechanical strengths lower. SEM analysis indicates that these decreases may be the consequence of a bad bond existing between the cement paste and OPS aggregate. Though, the compressive strength of OPS concrete which is 28 days old is acceptable for structural concrete. OPS concrete is more ductile and has a better thermal behavior compared to CGA concrete. (Resume d'auteur)

It is shown that a small system in thermodynamic equilibrium with a finite thermostat can have a q-exponential probability distribution which closely depends on the energy nonextensivity and the particle number of the thermostat. The distribution function will reduce to the exponential one at the thermodynamic limit. However, the nonextensivity of the system should not be neglected., 13 pages, 4 figures

CBA (coal bottom ash) is an industrial waste generated by coal fired thermal power plant. In this work, we investigate the utilization as an additive material in composite cement of CBA resulting from the firing of the coal extracted in Tefereyre mine (TCBA) in a thermal power plant in Niger. Our investigations are carried out by using compressive mechanical tests on 40 × 40 × 160 mm 3 mortar specimens. These mortar specimens are made with a partial substitution of the cement by TCBA at levels of 0%, 5%, 10%, 15%, 20% and 25% by mass. The tests were performed on the specimens at 7, 14, 28, 45 and 56 days of age. The results were used to evaluate the pozzolanic activity index as the ratio of the compressive strength of mortar containing 25% of coal bottom ash on that of the control mortar containing 100% of cement, according to ASTM C618. From these data, the maximum rate of TCBA addition in Portland cement was derived. It was found that TCBA has a pozzolanic activity index of about 71% at 28 days and displays a maximum substitution rate of 15% in Portland cement. These results strongly support the development of composite cement using TCBA.

This research is part of a process of valorization of local industrial by-products in the cement industry. lt focuses on the possibility f using coal bottom ash powder produced by SONICHAR in Niger as cement partial addition. After a physicochemical and environmental characterization of the coal bottom ash powder, we determined its pozzolanic reactivity and it mechanical activity index. The results show that the coal bottom ash powder presents a pozzolanicity whose relatively slow kinetics do ne start before 14 days. On the other hand, this coal bottom ash can be considered as a mineral addition of type 11 according to the standard EN 206-1 with an activity index of 0.76. This is why we used it to develop three CEM 11/A composite cements with a strength class of 42.5 when the substitution rate is 10% and a strength class of 32.5 when the rate of substitution is 15% and 20%. Normal mortars have been formulated with these cements and are characterized physically and mechanically. The durability of the mortars has also been studied, in particular from the point of view of the kinetics of carbonation and leaching in the presence of ammonium nitrate. Finally, it appears that the coal bottom ash powder may indeed be incorporated as an addition in the preparation of composite cements. The long-term mechanical characteristics (90 days) and the durability of the mortars made from these cements are preserved when the substitution rate does not exceed 10%., Ce travail de recherche s'inscrit dans une dynamique de valorisation des sous-produits industriels locaux dans l'industrie cimentière. Il porte essentiellement sur la possibilité d'utiliser la poudre de mâchefer de charbon produit par la SONICHAR au Niger pour élaborer des ciments composés. Après une caractérisation physico-chimique et environnementale de la poudre de mâchefer, nous avons déterminé sa réactivité pouzzolanique et son indice d'activité mécanique. Les résultats montrent que la poudre de mâchefer présente une pouzzolanicité dont la cinétique relativement lente ne démarre pas avant 14 jours. D'autre part, ce mâchefer peut être considéré comme une addition minérale du type Il selon la norme EN 206-1 avec un indice d'activité de 0,76. C'est pourquoi nous l'avons utilisé pour élaborer trois ciments composés de type CEM 11/A avec une classe de résistance de 42,5 lorsque le taux de substitution est de 10% et une classe de résistance de 32,5 lorsque Je taux de substitution est de 15% et 20%. Des mortiers normaux ont été élaborés à partir de ces ciments et caractérisés sur les plans physiques et mécaniques. La durabilité des mortiers a également été étudiée notamment du point de vue de la cinétique de carbonatation et de lixiviation en présence de nitrate d'ammonium. Il ressort en définitive que la poudre de mâchefer peut bien être incorporée comme addition dans l’élaboration de ciments composés. Les caractéristiques mécaniques à long terme (90 jours) et la durabilité des mortiers confectionnés à partir de ces ciments sont conservées lorsque le taux de substitution n'excède pas 10%.

This research is part of a process of valorization of local industrial by-products in the cement industry. lt focuses on the possibility f using coal bottom ash powder produced by SONICHAR in Niger as cement partial addition. After a physicochemical and environmental characterization of the coal bottom ash powder, we determined its pozzolanic reactivity and it mechanical activity index. The results show that the coal bottom ash powder presents a pozzolanicity whose relatively slow kinetics do ne start before 14 days. On the other hand, this coal bottom ash can be considered as a mineral addition of type 11 according to the standard EN 206-1 with an activity index of 0.76. This is why we used it to develop three CEM 11/A composite cements with a strength class of 42.5 when the substitution rate is 10% and a strength class of 32.5 when the rate of substitution is 15% and 20%. Normal mortars have been formulated with these cements and are characterized physically and mechanically. The durability of the mortars has also been studied, in particular from the point of view of the kinetics of carbonation and leaching in the presence of ammonium nitrate. Finally, it appears that the coal bottom ash powder may indeed be incorporated as an addition in the preparation of composite cements. The long-term mechanical characteristics (90 days) and the durability of the mortars made from these cements are preserved when the substitution rate does not exceed 10%.; Ce travail de recherche s'inscrit dans une dynamique de valorisation des sous-produits industriels locaux dans l'industrie cimentière. Il porte essentiellement sur la possibilité d'utiliser la poudre de mâchefer de charbon produit par la SONICHAR au Niger pour élaborer des ciments composés. Après une caractérisation physico-chimique et environnementale de la poudre de mâchefer, nous avons déterminé sa réactivité pouzzolanique et son indice d'activité mécanique. Les résultats montrent que la poudre de mâchefer présente une pouzzolanicité dont la cinétique relativement lente ne démarre pas avant 14 jours. D'autre part, ce mâchefer peut être considéré comme une addition minérale du type Il selon la norme EN 206-1 avec un indice d'activité de 0,76. C'est pourquoi nous l'avons utilisé pour élaborer trois ciments composés de type CEM 11/A avec une classe de résistance de 42,5 lorsque le taux de substitution est de 10% et une classe de résistance de 32,5 lorsque Je taux de substitution est de 15% et 20%. Des mortiers normaux ont été élaborés à partir de ces ciments et caractérisés sur les plans physiques et mécaniques. La durabilité des mortiers a également été étudiée notamment du point de vue de la cinétique de carbonatation et de lixiviation en présence de nitrate d'ammonium. Il ressort en définitive que la poudre de mâchefer peut bien être incorporée comme addition dans l’élaboration de ciments composés. Les caractéristiques mécaniques à long terme (90 jours) et la durabilité des mortiers confectionnés à partir de ces ciments sont conservées lorsque le taux de substitution n'excède pas 10%.