Publications Scientifiques
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Item Reliability assessment of carbon/epoxy micro-fiber subject to compressive stress(Emerald Publishing, 2024) Chebbab, Brahim; Ragueb, Haroun; Ifrah, Walid; Behnous, DounyaPurpose: This study addresses the reliability of a composite fiber (carbon fibers/epoxy matrix) at microscopic level, with a specific focus on its behavior under compressive stresses. The primary goal is to investigate the factors that influence the reliability of the composite, specifically considering the effects of initial fiber deformation and fiber volume fraction. Design/methodology/approach: The analysis involves a multi-step approach. Initially, micromechanics theory is employed to derive limit state equations that define the stress levels at which the fiber remains within an acceptable range of deformation. To assess the composite's structural reliability, a dedicated code is developed using the Monte Carlo method, incorporating random variables. Findings: Results highlight the significance of initial fiber deformation and volume fraction on the composite's reliability. They indicate that the level of initial deformation of the fibers plays a crucial role in determining the composite reliability. A fiber with 0.5% initial deformation exhibits the ability to endure up to 28% additional stress compared to a fiber with 1% initial deformation. Conversely, a higher fiber volume fraction contributes positively to the composite's reliability. A composite with 60% fiber content and 0.5% initial deformation can support up to 40% additional stress compared to a composite containing 40% fibers with the same deformation. Originality/value: The study's originality lies in its comprehensive exploration of the factors affecting the reliability of carbon fiber-epoxy matrix composites under compressive stresses. The integration of micromechanics theory and the Monte Carlo method for structural reliability analysis contributes to a thorough understanding of the composite's behavior. The findings shed light on the critical roles played by initial fiber deformation and fiber volume fraction in determining the overall reliability of the composite. Additionally, the study underscores the importance of careful fiber placement during the manufacturing process and emphasizes the role of volume fraction in ensuring the final product's reliability.Item Assessment of the aggressive agents' penetration into concrete by non-destructive techniques(Emerald Publishing Limited, 2022) Khial, Nassima; Chaid, RabahPurpose: Around the world, many structures are affected by pathological reactions between the concrete and the surrounding environment in which these structures are designed, these pathologies lead to compromise their serviceability. In this context, this paper aims to study the durability of concrete in different environments with non-destructive techniques, by studying its contamination by the aggressive agents’ penetration. And this, by evaluation of the influence of the durability indicator that is the absorption by immersion, on the mechanical properties (compressive strength, modulus of elasticity and damage), of specimens having undergone immersion/drying cycles, in different aggressive media (water, seawater and acids: sulfuric and acetic with a concentration of 5%). Design/methodology/approach: Concrete specimens were manufactured in the laboratory, and then underwent immersion/drying cycles, in parallel, the weight gain of the specimens was carried out in the wet state after immersion and in the dry state after drying, and the ultrasonic speeds were also taken in a dry state. The results showed a decrease in the mechanical properties studied, namely, the compressive strength as well as the elastic properties (modulus of elasticity, damage) as a function of the increase in absorption, and that the weakest properties are those of test specimens submerged in water. Findings: Non-destructive tests have shown that the parameters examined increase with the immersion/drying cycles, up to the fourth cycle. Beyond that, they drop gradually, and this is valid for four environments. This decline is due to the degradation of cement pastes exposed to water, seawater and acid attacks. This is explained by the greater or lesser dissolution of all the major elements making up the cementitious matrix (CSH, Ca(OH)2, CaO, SiO2, C3S, C2S, C3A, C2S) depending on the nature and concentration of the chemical substances evacuated. The results showed that the highest absorption rate and damage are those recorded for the specimen immersed in water, followed by that of the specimens immersed in acids, followed by that of the specimen immersed in sea water. The highest compressive strength and stiffness are those of the specimen immersed in sea water, followed by that immersed in acids, then in water. Originality/value: The work developed aimed to study the durability of concrete, by addressing the study of the coupling absorption – mechanical characteristics of concrete, in different aggressive media (water, seawater and acids), to seek a relationship between these parameters. The tests provided are non-destructive tests, which consist of taking measures that do not damage the concrete. They allow indirect measurements of the mechanical properties of concrete as well as the monitoring of their evolution over time. They also allow having certain accuracy, because the measurements are taken at the same placeItem Mechanical performance of metakaolin-based geopolymer mortar blended with multi-walled carbon nanotubes(Elsevier, 2022) Oualit, Mehena; Irekti, AmarIn recent decades, the cement industry has been viewed as a major environmental problem mainly due to carbon dioxide CO2 emissions during the production of Portland Cement (PC). Among the solutions to this problem is to replace Portland cement-based materials with alkali-activated materials. Metakaolin-based geopolymer mortars are currently considered a serious alternative to ordinary Portland cement mortar due to its various advantages. The present experimental study aims to develop metakaolin-based geopolymer mortars reinforced with multi-walled carbon nanotubes (MWCNTs). The content of MWCNTs incorporated was 0.1; 0.2; 0.3, and 0.4 wt%, respectively, with respect to the mass of metakaolin. A mixture without the addition of carbon nanotubes was also prepared and used as a reference (control sample). The alkaline activation of metakaolin was carried out using aqueous sodium silicate solution having a molar ratio (SiO2/Na2O) equal to 1.77. Mechanical characterization of the hardened samples was performed after curing for 3, 7 and 28 days. The results indicate that the incorporation of multi-walled carbon nanotubes in the geopolymer matrices improves compressive strength. Microscopic analysis has shown that these carbon nanotubes contribute to the densification of the geopolymer matrix and give rise to crack bridging mechanisms. The highest value of the compressive strength was recorded using an alkali silicate content equal to 8 (expressed as a percentage of Na2O) combined with 0.2% of multi-walled carbon nanotubes in the geopolymer mortar. The integral absolute error (IAE) calculated on the compressive strength values at different curing ages are all within an acceptable range (0–10%)Item Impact of the nature of fibers on the physicomechanical behavior and durability of cement matrices(Springer, 2021) Aboutair, Wafaa; Chaid, Rabah; Perrot, ArnaudIn this paper, the strength of concrete prismatic and cylinders concrete and reinforced with steel and polypropylene fibers are presented. Also, hybrid fibers with crimped steel and polypropylene were used in concrete matrix to study its improvements in strength and durability properties. The steel, polypropylene, and hybrid consisting of polypropylene and steel (crimped) fibers of various proportions by volume of cement were used in concrete mixes. Besides cubes, cylinders of 160 mm diameter X 320 mm high of concrete were cast with steel fiber, polypropylene fiber, and hybrid fiber, respectively, by volume of cement. The water absorption test was conducted on 28 and 90 days, and the test results show that the addition of steel and polypropylene fibers to concrete exhibits better performance. The test results show that use of steel fiber-reinforced concrete improves compressive strength and split tensile strength. The durability of such concrete is also improvedItem Physical-mechanical properties of steel fibre-reinforced self-compacting concrete containing natural perlite addition(Inderscience Publishers, 2020) Mansour, S.M.The aim of this work is to highlight the effect of the Algerian natural perlite used as fillers addition on the workability and physical-mechanical properties of metallic fibre self-compacting concrete (SCC). Effect of the perlite is compared to that of silica fume fillers to replace limestone fillers. One control concrete without fibres containing limestone fillers, two concretes with silica fume or perlite fillers and six SCCs were elaborated with limestone, perlite and silica fume fillers separately containing 1% vol. of steel long wavy or short hooked fibres. Several tests were conducted for evaluating the workability properties in the fresh state, the density, mechanical strengths and elastic modulus in the hardened state. The results show the beneficial effect of the use of perlite as fillers. Workability properties decrease slightly but an increase of mechanical strengths and elastic modulus is much more marked with the use of the steel hooked fibresItem Use of refractory bricks as sand replacement in self-compacting mortar(Taylor & Francis Online, 2017) Aboutaleb, Djamila; Safi, Brahim; Chahour, Kahina; Belaid, AmraneThis present work investigate the possibility of using refractory bricks (RB) as fine aggregates (by partial and total substitution of natural sand) in self-compacting mortars (SMCs). For this, an experimental study was carried out to evaluate physical and mechanical properties ((bulk density, compressive and flexural strength) of the self-compacting mortars (SCMs) with partial and total substitution of natural sand (NS) by crushed refractory bricks (RB) at different ratio (BR/S= 0, 10, 30, 50 et 100%) by weight. The results obtained show that the RB (0/5 mm class), can be used as fine aggregates for self-compacting mortar, without affecting the essential properties of mortar. However, the performances of RB-based mortar (100% as sand), were better and are suitable for a fluid concrete (such as self- compacting concrete)Item Improved behaviour of mortars at a high temperature by using refractory brick wastes(Indersciences Publishers, 2015) Saidi, Mohammed; Safi, Brahim; Bouali, Khaled; Samar, Madjid; Benmounah, AbdelbakiItem Physico-mechanical properties and thermal behavior of firebrick-based mortars in superplasticizer presence(Elsevier, 2016) Saidi, Mohammed; Safi, Brahim; Benmounah, Abdelbaki; Megdoud, Nadjiba; Radi, FaizaItem Use of wood waste (Aleppo pine) as a superplasticiser in self-compacting mortars(2014) Daoui, Abdelhakim; Safi, Brahim; Rezak, M.; Zerizer, A.Item Fresh and hardened properties of self-compacting concrete containing plastic bag waste fibers (WFSCC)(Elsevier Ltd, 2015) Ghernouti, Y.; Rabehi, B.; Bouziani, T.; Ghezraoui, H.; Makhloufi, A.This paper presents the fresh and hardened properties of self-compacting concrete (SCC) containing plastic bag waste fibers (PBWF). Fibers were prepared by recycling waste material such as, plastic bag. Fourteen mixtures of SCC with 0.40 of water/cement ratio were studied, twelve SCC mixtures with plastic bag waste fiber (WFSCC) by varying the length of fibers (2, 4 and 6 cm) with different levels of incorporation (1, 3, 5 and 7 kg/m3) and two other mixtures, one with 1 kg/m3 of polypropylene fibers (PFSCC) and another without fiber as reference (RSCC). Slump flow, L-box, and sieve stability were performed to assess the fresh properties of the prepared mixtures. Compressive strength, splitting tensile strength and flexural strength of the concrete were determined for the hardened properties Test results show that mixtures based on PBWF with a length of 2 cm, met the criteria of self-compactability (evaluated by slump flow diameter, L-box and sieve stability test) regardless of the fibers content. The obtained results are very interesting, suggesting a possible use of PBWF for structural reinforcement of SCC, the presence of this fibers in concrete delaying the location of microcracks. Although, the incorporation of PBWF has not a significant effect on the compressive and flexural strengths, it has a important effect on the split tensile strength value at 28 days. The improvement varies from 4% to 74%, it depends on the amount of fibers, and it is not affected by the length of PBWF