Résumé: This study investigates the performance of sisal fiber-reinforced mortar enhanced with marble filler. To enhance compressive strength, marble waste was introduced as a partial cement replacement in increments of 5.0 % by weight. Additionally, sisal fibers were incorporated at varying proportions of 0.5 %, 1.0 %, and 1.5 % by weight of binder, utilizing two fiber lengths (6 mm and 12 mm). Given their potential to enhance mechanical properties, sisal fibers have gained attention as reinforcement in cementitious materials. Their morphology, physical characteristics, and chemical composition were analyzed in detail. A novel treatment approach was explored to mitigate the hydrophilic nature of sisal fibers. Prior to their integration into the mortar, the fibers underwent chemical modification using chelating agents—ethylenediaminetetraacetic acid (EDTA) and ammonium hydroxide (AM). The impact of these treatments was assessed through Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The study evaluated key physical properties, including workability, water absorption, and density, alongside mechanical properties such as compressive strength, tensile strength, and shrinkage. Experimental findings revealed that chemical treatments, particularly with EDTA, altered the fiber’s morphology by increasing surface roughness and reducing hydrophilicity, as evidenced by FTIR and SEM analyses. These modifications contributed to an approximately 4 % improvement in workability, notably in EDTA F-M (1 %) mortars. Furthermore, flexural tensile strength tests at 28 and 90 days demonstrated an increase of 22–23 % for EDTA-treated mortars. The inclusion of EDTA-treated fibers also led to a 13 % reduction in total shrinkage. Thermogravimetric analysis (TGA) confirmed that the EDTA-treated fibers enhanced cement hydration, leading to the formation of greater amounts of hydration products such as calcium silicate hydrate (C-S-H) and ettringite compared to untreated fibers. Overall, the findings affirm that sisal fibers can effectively reinforce mortar, and chemical treatment with EDTA significantly improves both physical and mechanical properties. This approach presents a viable strategy for developing sustainable and high-performance cementitious composites in construction.

Résumé: In this work, it was proposed to replace the conventional reinforcement of the unsaturated polyester resin by a mineral, from a siliceous volcanic rock of volcanic nature, perlite. UPR/perlite composites with different proportions of phase components (from 1% to 5% of powder mass part). We used unsaturated polyester resin (UPR) as well as the hardener cobalt octoate and treated and untreated perlite of different dimensions (greater than 60µm, and less than 60µm). The composites were prepared by the contact molding process. The composite plates are hardened for 24 hours at room temperature then placed in an oven for 15 hours at 50°C to undergo post-curing. The composites obtained were subjected to different characterization techniques, namely rheological tests (dynamic mechanical analysis (DMA)), thermal tests (differential calorimetric analysis (DSC)) and Thermogravimetric analysis (ATG) and structural characterization by Fourier transform infrared (FTIR). The DMA measurements showed that the UPR/perlite composites with untreated filler presented conservation modules higher than that of the resin without perlite for the rates of 3% and 4%, while for the composites with treated filler, that at 3% of perlite shown the highest modulus along the glassy zone. Also, the glass transition temperature of the UPR resin was not affected by the addition of perlite. The decrease in intensity at mid-height of the tan δ peaks allowed deducing the existence of a fairly strong UPR/perlite interface. DSC thermograms showed that the exothermic peak is shifted to higher temperatures, due to a delay in the curing reaction caused by the presence of the perlite particles. This study concluded that the perlite enhances the properties of composites.

Résumé: The susceptibility of concrete to elevated temperatures is a paramount concern in civil engineering, especially in fire-related scenarios. This material often suffers mechanical weaknesses such as fracturing and reduced durability under high temperatures. Despite its ubiquitous use, concrete’s vulnerability to thermal stress presents significant challenges for maintaining structural integrity and safety. The novelty of this work lies in its innovative approach to addressing these challenges by proposing the utilization of waste plastic fibers, which are readily available due to the extensive use of various plastic products. This approach not only enhances the mechanical resilience of concrete but also contributes to mitigating environmental and health impacts associated with plastic waste. The research focuses on the effects of high temperatures on the mechanical properties of sand concrete reinforced with fibrous materials. Concrete specimens were prepared with different lengths (1 cm and 2 cm) of packing tape fibers at concentrations of 1% and 2%. These specimens underwent controlled thermal treatments ranging from 100 °C to 700 °C with a heating rate of 1 °C/min, following a 90-day water immersion curing period. The evaluation encompassed various tests including visual inspection, residual weight measurement, residual compressive and tensile strength assessments, and ultrasonic pulse velocity (UPV) testing. The analysis revealed a notable improvement in mechanical strength for concrete reinforced with 1% fibers at 300 °C. However, exposure to higher temperatures (500 °C and 700 °C) led to a significant decline in strength across all samples due to the evaporation of fibers, resulting in the formation of voids and conduits within the concrete’s structure. While previous research has extensively investigated the effectiveness of polypropylene fibers in crack mitigation during fire incidents, limited attention has been given to the potential of plastic waste as a reinforcement material. Thus, this study’s novelty contributes to expanding the scientific understanding of using waste plastic fibers to enhance concrete’s resilience to high temperatures, thereby filling a crucial gap in existing literature.

Résumé: Current design trends indicate a rising preference for mixed steel-concrete structures, which provide exceptional opportunities for material optimization and numerous advantages, including improved strength, ductility, and stiffness. This trend aligns with the growing demand for sustainable and resilient construction solutions in civil and structural engineering. The present article provides an analytical and numerical investigation focused on enhancing the performance of cold-formed steel back-to-back C-columns through the application of various strengthening materials, including concrete and carbon fiber-reinforced polymer (CFRP) layers. The study employs advanced finite element modeling techniques to simulate real-world loading conditions and incorporates rigorous parametric analyses to evaluate structural behavior under varying constraints. Furthermore, it investigates the impact of incorporating different types of web stiffeners—namely, simple, square, and triangular—on the mechanical behavior of built-up columns subjected to axial compression. The research also explores how these configurations influence load distribution and failure mechanisms. To validate the analytical approaches, the numerical findings are compared with predictions based on EN 1994-one to one standards, allowing for an evaluation of the effectiveness of the formulations in estimating the contributions of individual components. The results indicate that the addition of concrete significantly enhances the strength and lateral stability of built-up empty columns, with improvements of approximately 70% and 75%, respectively. Conversely, the application of CFRP strips leads to a reduction in lateral instabilities by about 80%. Additionally, the combined use of concrete and CFRP materials demonstrates synergistic benefits, offering a balanced enhancement of both compressive strength and lateral stability. These findings provide essential insights for optimizing the design and performance of thin-walled structures in engineering practice. The study emphasizes the practical implications of these results for designing lightweight, high-performance structures that meet modern construction demands.

Résumé: Several studies have explored the potential of waste marble powder (WMP) and lime (LM) as solutions for issues associated with clayey soils. While WMP enhances mechanical properties and addresses environmental concerns, LM effectively improves soil characteristics. This research investigates the efficacy of LM and WMP, both individually and in combination, in addressing challenges specific to clayey soils in Bouzaroura El Bouni, Algeria. These soils typically exhibit low load-bearing capacity, poor permeability, and erosion susceptibility. LM demonstrates promise in enhancing soil properties, while WMP not only addresses environmental concerns but also enhances mechanical characteristics, providing a dual benefit. The study utilizes a three-variable experiment employing Response Surface Methodology (RSM) Box-Behnken Design, with variations in clay content (88%–100%), LM treatment (1.5%–9%), and WMP inclusion (1.5%–9%). Statistical analysis, including ANOVA, reveals significant patterns with p-values <5%. Functional relationships between input variables (clay, LM, and WMP) and output variables (cohesion, friction angle, and unconfined compressive strength) are expressed through high determination coefficients (R2 = 99.84%, 77.83%, and 96.78%, respectively). Numerical optimization identifies optimal mixtures with desirability close to one (0.899–0.908), indicating successful achievement of the objective with 88% clay content, 3% LM, and 6% WMP. This study provides valuable insights into optimizing clay soil behavior for environmental sustainability and engineering applications, emphasizing the potential of LM and WMP as strategic additives.

Résumé: At ambient temperature, concrete exhibits excellent mechanical properties. However, understanding the behavior of concrete under high-temperature conditions is crucial, especially for civil engineering applications during fire incidents. The growing use of plastic-based products has led to a significant increase in polymer waste, posing environmental challenges. The valorization of this plastic waste in the form of fibers presents both economic and environmental advantages. This study focuses on the study of the behavior of sand concrete incorporating polyethylene terephthalate (PET) fibers with percentages of 1% and 2% at high temperatures (100, 300, 500 and 700 °C). Specimens are tested for residual mass loss, residual compressive and tensile strength. A complementary analysis of SEM makes it possible to confirm and better clarify the morphology of the concretes of sand before and after the rise in temperature. The results obtained from this study indicate that the residual resistance is reduced with the rise in temperature for all the concretes studied, except in the temperature range of 300 °C, in which a slight improvement in resistance is noticed. The incorporation of PET fibers in the test concretes does not enhance their residual behavior significantly. However, it does serve as an effective solution by reducing the susceptibility to spalling, by preventing cracking and by fulfilling a similar role to that of polypropylene fibers.

Résumé: This article presents the results of a comparative experimental study on the influence of date palm fibers to replace polypropylene fibers used as reinforcement in self-compacting concrete (SCC). Indeed, the use of polypropylene fibers makes it possible to reduce the plastic shrinkage of concrete. Date palm fibers have mechanical characteristics (tensile strength and elasticity modulus) largely sufficient to replace polypropylene fibers. The use of natural fibers has several advantages, they are natural, renewable, have no effect on the environment and require little energy for their transformation unlike synthetic fibers. In this comparative study, polypropylene fiber is used as a control material and date palm fiber as a study material. The results obtained show that the two types of fibers decrease the fluidity and the compressive strength, increase the flexural strength and decrease the shrinkage. Date palm fibers delay the appearance of cracks more than polypropylene fibers. Date palm fibers guarantee the best results of SCC in fresh and hardened state.

Résumé: The use of finite element calculations to deal with geotechnical problems is therefore limited by poor knowledge of the mechanical parameters of soils. The identification of these parameters characterizing the soil behavior model involves solving the inverse analysis problem. This form of inverse analysis consists in calibrating a numerical soil model on experimental data by iterative modifications of the values of the input parameters of the model until the difference between the result of the numerical calculation and the experimental data is minimal. In this article, we study the use of the principle of inverse analysis for the identification of the parameters of the constitutive soil model Mohr–Coulomb: the shear modulus (G) and the friction angle (φ). The inverse analysis problem posed by the determination of the parameters of the model is solved using an optimization technique based on two stochastic optimization algorithms, the genetic algorithm and the hybrid genetic algorithm with the tabu search method. These two optimization methods have been validated on a pressuremeter test. The results obtained by applying the genetic algorithm method and the hybrid genetic algorithm method for the identification of the two Mohr–Coulomb parameters (G and φ) show that the hybridization process of the genetic algorithm with the tabu search method accelerated the convergence of the algorithm towards the exact solution of the problem whereas the genetic algorithm alone takes a much longer computation time to reach an optimum close to the exact solution of the problem.

Résumé: Volume change of expansive soils is a challenging issue, which affects various engineering structures all over the world. Consequently, we need environmentally-friendly and cost-effective soil stabilizers to address the challenges related to expansive soils. The utilization of natural fibers allows for the reduction in environmental impact since they are renewable and biodegradable raw materials. Moreover, the current article presents an experimental approach to study the effect of natural fibers on the mechanical behavior of expansive soils. Various experimental tests—such as Atterberg limits, standard compaction, direct shear, swelling potential, and swelling pressure—were conducted on control and treated soil samples using different percentages of fibers. The results of measurements of the physico-mechanical properties after reinforcement of the soil with 1%, 5%, and 10% of natural fibers indicate that the mechanical behavior of expansive soils is greatly influenced by the addition of natural fibers. To conclude, 86% reduction was observed in the swelling coefficient of treated soil. Future research can be done to check the durability of the current practice in detail.

Résumé: This research focuses on the optimization of formulation, characterization, and damage analysis of plant fiber-reinforced polyester resin composites (jute and date palm). To better understand the characteristics and mechanical behavior of these materials, this study investigates the influence of resin content and plant fibers on the physico-mechanical behavior of the resin composites. Resinous composites consisting of polyester resin and raw earth were studied using a novel formulation based on an empirical method that follows the principle of earth saturation with polyester resin. Saturation was achieved with a 28% content of polyester resin, which appeared to be an optimal blend for the earth–resin composite. Plant fibers were randomly incorporated as reinforcement in the composites at various percentages (1%, 2%, and 3%) and lengths (0.5 cm, 1 cm, and 1.5 cm). Mechanical tests including bending, compression, and indentation were conducted to evaluate the mechanical properties of the composites. Analysis of fracture morphology revealed that the deformation and rupture mechanisms in bending, compression, and indentation of these composites differ from those of traditional concrete and cement mortar. The obtained results indicate that the composites exhibit acceptable performance and could be favorably employed in the rehabilitation of historic buildings.

Résumé: The wide use of cold-formed sections (CFS) in the field of steel constructions, favored by the multiple advantages they offer (lightness, ease of installation, etc.), has led us to reflect on a new process for manufacture of metal beams allowing the design of very large span hangars and a reduction in instability problems. This paper presents a study of the theoretical and numerical behavior of a large span CFS beam with different webs, a solid web, a triangular corrugated web, and a trapezoidal corrugated web. These beams are stressed by a concentrated bending load at mid-span. Numerical modeling was done using the finite element software ABAQUS. The results were validated with those theoretically found, based on the effective width method adopted in standard EN1993-1-3. The load capacity and failure modes of the beams were discussed. According to numerical and analytical analysis, corrugated web beams perform better than all other sections.

Résumé: High performance concrete (HPC) is an innovative concrete used widely in modern construction. New techniques of formulating and designing HPC have made it possible to obtain remarkable mechanical performance and durability compared to the conventional concrete. The main advantages of HPC are related to its low porosity, very high mechanical resistance, and excellent durability. The ease of HPC application is obtained by the combined use of superplasticizer and mineral addition, which results in a significant increase in the compressive strength while improving workability and durability. The Algerian steel industry in North Africa generates very large quantities of slag which are currently little or not used for the formulation of hydraulic binders in the field of construction materials. In the current economic climate, research on high-performance concretes in Algeria is mainly focused on their formulations with a view to producing cement-based concretes composed of better strengths and more durable. The objective of this work is to optimize a formulation of HPC based on a ternary binder integrating granulated Algerian blast furnace slag as a cement substitute. This can partially solve an environmental problem by recycling waste and by-products from the steel industry. The manufacture of a HPC with less cement could lead to both environmental benefits thanks to a reduction in CO2 emissions and financial benefits through a lower construction cost and build more sustainable structures.

Résumé: Cold-formed steel (CFS) structural members retain their preferred position in the lightweight construction industry, which is due to their significant advantages. The optimization of these CSF elements will make it possible to construct buildings at very competitive prices, having in addition an increased load capacity, and thus obtaining a stable and economical construction. The main objective of this research being the evaluation of the effectiveness of these new sections in (CSF) and the estimation of the remarkable instabilities as well as the failure modes. This article deals with an experimental study on the behavior of CSF beams of delta and bi-delta shape, solicited by four-point bending loads. These cross section shapes are often used in floors as main and secondary beams. The properties of this type of sections are most often based on the method involving the effective width designated by the Eurocode 3 standard. A nonlinear analysis by finite elements (FE) using the ABAQUS calculation program is carried out, thus making it possible to compare the experimental results with the numerical ones as well as those which are given by the theory proposed by Eurocode 3. Finally, the results obtained essentially showed that the failure modes of the delta and bi-delta beams corresponded to the buckling modes local.

Résumé: This paper is concerned with investigating of the plastic behaviour on gap K-joints of truss girders, made from thin-walled rectangular hollow section members. An experimental study was carried out on a full-scale girder under a concentrated load on two central nodes. A numerical analysis was carried out using ABAQUS in order to clearly see the behaviour of this type of joint and to make a comparison with the experimentation. This study will make it possible to examine attentively and to define the analytical model for this type of joint. The results obtained in this paper have shown that the sections with very thin-walled present different behaviours compared to the thin or more or less thick sections. As a result, the tested truss made it possible to observe the failure mode of this type of section, follow-up of a comparative study on the determination of the joint capacity by Eurocode 3 and CIDECT.

Résumé: The reuse of concrete waste as a secondary aggregate could be an efficient solution for sustainable development and long-term environmental protection. However, the variable quality of waste concrete, especially with various compressive strengths, can have a negative effect on the final compressive strength of recycled concrete. In this approach, the major goal of this research is to study the effect of parent concrete qualities on the performance of recycled concrete. To accomplish this task, three grades of different compressive strengths (10 to 15) MPa, (20 to 25) MPa, and (30 to 40) MPa have been analyzed in an experimental test program, in which an unknown compressive strength is introduced as well. The experimental mix use 40% of secondary aggregates (both course and fine) and 60% of natural aggregates. This led to the decreasing of the compressive strength of the test concrete between 14% and 23.7% compared to the normal concrete. This loss was improved by adding an amount of cement equivalent to 4% of the weight of the recycled aggregate used. The achieved results prove that the strength properties of the parent concrete have a limited effect on the compressive strength of the recycled concrete. Additionally, low compressive strength parent concrete, when crushed, generates a high amount of fine aggregate and large percentage of recycled coarse aggregates with less attached mortar, and presents the same compressive strength as an excellent parent concrete.

Résumé: The valorization of local by-products in the manufacture of a new range of sand concrete and the improvement of their properties, will lead to seek an arrangement between performance and cost in order to achieve a resistant material. Waste recycling affects two very important affect namely the environmental impact and the economic impact. The main objective of our work is to contribute to optimize the formulation of sand concrete as part of the recovery of waste, which is harmful to the environment given its bulky and unattractive nature, it is waste plastic. Most PET bottles become waste after use, causing environmental problems. To solve this problem, a method for recycling PET bottles as fibers to strengthen concrete is proposed. Two types of plastic waste are added to sand concrete; the first concerns the recycling of post-consumer bottles in PET, in the form of polyester fiber supplied by the company RET-PLAST and the second type concerns the packaging belts made of polyethylene terephthalate (PET). The properties in the fresh state (workability and density) and in the hardened state (compressive strength, tensile strength and water absorption) of the various produced concretes are analyzed and compared against their respective controls. From the experimental results, it can be concluded that the reinforcement of the cement matrix with PET fibers with a rate of 1% improves the mechanical properties of sand concrete as well as a remarkable decrease in its water absorption capacity.

Résumé: This paper deals with the development of sustainable building earth-based materials. More precisely, it addresses the study of the reinforcement of raw earth with natural fibres originated from Algeria (diss and date palm tree fibres) and their stabilisation with xanthan gum. The aim of this study is the design of extruded earth-based building blocks with improved mechanical properties such as compressive strength and ductility. The effects of separate and simultaneous addition of date palm trees or diss fibres (with length varying between 5 and 15 mm at dosages of 1.5 and 3% in volume) and stabiliser (xanthan gum and HMP at 1 and 2% of the dry earth mass) on the flexural and compressive strength of the stabilised and unstabilised extruded materials are compared. Results show that adding only fibers decreases the compressive strength of the earth in comparison with the unreinforced sample. It is also shown that diss fibres provides better reinforcing efficiency than date palm tree fibres and that a combined addition of xanthan gum and natural fibres create a synergic effect that greatly improved the material mechanical behaviour: higher compressive and tensile strengths and better ductile properties. These results are fully supported by microscopic observations and pull-out tests carried out on single fibres.

Résumé: Enhancing existing steel structures becomes imperative upon alterations in usage or geometric configurations, such as introducing web openings in floor beams to accommodate various services. The utilization of welded steel plate and conventional strengthening methods often presents challenges, which may be mitigated through the adoption of composite materials like Fiber Reinforced Polymers (FRP). However, research on the application of FRP to steel beams with web openings remains limited, predominantly focusing on beams with rectangular openings of modest dimensions. This study delves into the application of Glass Fiber Reinforced Polymers (GFRP) to strengthen reinforced steel floor beams featuring trapezoidal openings. Leveraging a rigorously validated numerical model derived from previously published findings by a contributing researcher, the investigation showcases that the proposed GFRP reinforcement scheme exhibits performance comparable to conventional steel plate welding techniques, while preserving the inherent strength of the original solid beams.