Résumé: This article presents the results of an experimental study on the effect of elevated temperatures, ranging from 20 to 500, 700, and 1000 °C, on the physico-mechanical properties of polypropylene fiber-reinforced recycled aggregate concrete (FRRAC). Two polypropylene (PP) fiber lengths, 12 and 18 mm, with a fixed dosage of 0.2% of the concrete volume and increasing recycled concrete aggregate (RCA) content of 20, 40, 60, 80, and 100%, were used. Fresh-state results show that adding PP fibers in FRRAC reduces its workability, while using RCA improves it, although RCA decreases the concrete’s density. After heating-cooling cycles, weight loss increases with temperature, amplified by RCA and PP fibers, which create porosity after melting. Capillary absorption and concrete swelling increase with tempera- ture, while PP fibers limit shrinkage at ambient temperature. Compressive and tensile strength significantly decrease from 700 °C, and the elastic modulus degrades with increasing temperature and RCA content. However, PP fibers reduce crack openings, especially the 18 mm fibers, and prevent explosive spalling, even at 1000 °C.

Résumé: In construction, a recent direction is to examine and integrate alternative sources of building materials with the goal of substituting the use of natural materials. This transition is encouraged by growing concern among policymakers and researchers regarding the environmental footprint of the construction industry. The incorporation of recycled aggregates into cementitious materials, such as concrete or mortar, results in a deterioration of their mechanical performance and their durability. Scientific studies devoted to recycled concrete have demonstrated that it is affected by the introduction of these recycled aggregates, in particular by the use of recycled sand. The latter is characterized by the presence of significant proportions of hardened cement, particularly that coming from a recycling plant. In this work, we aim to study experimentally the influence of the nature of recycled sand on the properties of cement mortars, substituting natural sand, with different percentages by volume: 0, 15, 30, 40, 50 and 75 %, by two types of recycled sand, one from the crushing of structural concrete and the other from a recycling plant. The mortar mixtures were made from CEM I 52.5 and Sand/Cement ratio = 3. The plasticity of these mortars was kept constant and the recycled sands have been pre-wetted. The comparative study between the different compositions of recycled mortars has shown that the physical and mechanical properties are influenced by the incorporation rate of the recycled sand. Of which, increases in the compressive strengths of recycled mortars were recorded, particularly those based on sand from the crushing of structural concrete, compared to the control mortar based on natural river sand. However, the flexural strengths of the recycled mortars suffered a slight reduction compared to the reference mortar.

Résumé: Despite the implementation of a national action plan and a deployed monitoring of intoxications, Algeria deplores each year more than 2000 victims, who require immediate medical care, and a hundred deaths. For this reason, the risk of carbon monoxide poisoning is not negligible in confined spaces. The gases used or generated by certain work processes or household appliances can impoverish the air. When the oxygen content in the air, is usually 21%, it decreases to less than 15%, which creates a risk of carbon monoxide poisoning. Under-oxygenation leads to the physical and mental capacities’ reduction, with the victim’s unawareness of it. At 10% of oxygen in the air, the victim faints. Below 10% the victim dies within minutes, unless immediately rescued. Through this research, we are trying to highlight the dangers associated with faulty domestic appliances (heating, water heaters, barbecues, etc.), mainly affecting low class population. This poisoning, preventable and treatable, is a public health issue, which must be treated urgently, mainly during the winter period. Keywords: carbon monoxide, assessment, asphyxia, household appliances and poisoning

Résumé: Due to rapid urbanization on a global scale, a significant challenge has emerged, with the construction industries becoming the primary threat to natural resources and the environment. The valorization of construction and demolition waste (C&DW) is perceived as a promising solution, offering notable benefits in terms of economic and environmental constraints. However, the use of recycled aggregates in concrete may be limited from a technical perspective, particularly concerning the durability of constructions. In this context, our experimental study was conducted to assess the impact of particle size distribution and the quality of recycled coarse aggregates on the mechanical and durability properties of concrete. Three particle size classes and two types of recycled aggregates from old and recent concretes were used. The experimentation involved comparing the mechanical strengths under uniaxial compression and splitting tensile tests of these different concretes, as well as their water and gas permeabilities. The results of this comparative study have shown that recycled coarse aggregate, especially the fine fractions, exhibit superior transport properties for liquid and gas agents compared to natural aggregates, which aligns with the observations found in the literature. On the other hand, the mechanical strengths of recycled concrete are similar to those of natural concrete.

Résumé: The sustainable management of inert waste is a global environmental and sustainable development issue, particularly acute in developing countries. Construction and demolition waste, which accounts for about 75% of all inert waste, plays a central role in the waste problem. In Europe and developed countries, C&DW's management focuses on prevention and recycling as preferred approaches. The first aims to reduce the generation of this waste from the outset, by embedding sustainability principles in buildings and using construction methods to minimise waste throughout its life cycle. The latter is based on the recovery and recycling of C&DW materials. In Algeria, landfilling in technical landfills (CET) remains the main method of treatment of waste, whether household or inert. However, due to the limited number of TECs, their inadequate location and rapid saturation, even for newer facilities, illegal landfills have become a frequently adopted solution, accounting for almost 60% of the waste disposed of. This is the result of several factors, including the lack of an adequate legislative framework, the inadequacy of treatment methods for the nature of the waste, and the lack of public awareness. In this context, our work aims to propose alternatives to landfilling, appropriate solutions that will reduce the negative environmental impacts of this waste and contribute to the preservation of natural resources. These solutions are based on an integrated approach that combines waste prevention, recycling and recovery, including C&DW. They must be designed taking into account the specificities of the Algerian context, including legislative and institutional constraints, economic considerations, and local cultural habits.

Résumé: Today, the universal need to preserve resources, protect the environment, and use energy wisely must be reflected in the field of concrete technology. The recycling of construction and demolition waste (C&DW) as a source of aggregates for concrete production is attracting increasing interest from the construction industry. The valorization of recycled aggregates, which is already well established in the public works sector but less widespread in civil engineering works, seems to be an ideal and promising solution to solve the problems associated with C&DW. In this context, our work aims to integrate aggregates from demolition concrete as an alternative to natural aggregates in the manufacture of hydraulic concrete. However, the high porosity and less performant mechanical properties of recycled aggregates have an impact on the properties of concrete. For a long-lasting concrete, it is necessary to meet standards for water, gas permeability, and resistance to ion diffusion. This experimental study presents the results of physical and mechanical characterizations of the aggregates used, including recycled aggregates, as well as their influence on the properties of concrete in fresh and hardened state. The characterization of the materials used revealed that recycled aggregates have some heterogeneity, high absorption capacity due to their porosity, and therefore medium-quality hardness. The mechanical strengths of concretes based on recycled aggregates from demolition concrete are acceptable compared to those of concretes with natural aggregates. These mechanical performances demonstrate that, without requiring any special technologies, recycled aggregates can be used to obtain structural concretes with characteristic strengths ranging from 25 to 30 MPa.

Résumé: La valorisation des coproduits industriels issu de la production de l'acier revêt une importance croissante dans notre société . Elle représente une démarche importante et une étape cruciale dans la transition vers une économie circulaire et durable. Le laitier de haut-fourneau (LHF) est un sous-produit de la sidérurgie, n'est plus simplement considéré comme un déchet. Autrefois perçu comme un encombrement à éliminer. Grâce aux progrès des techniques, ils sont passés de ce statut négatif, à celui d'un coproduit de la sidérurgie, dont l'éventail des propriétés est aujourd'hui apprécié et recherché. Récemment, les LHF sont largement utilisé comme matériau de construction. Grace à ses propriétés de liaison en font un excellent composant pour la fabrication de ciment, de béton et d'asphalte. Dans ce contexte, cette étude vise à explorer les multiples applications des LHF dans les secteurs des travaux publics, des infrastructures de base et la construction. Nous prendrons en compte les méthodes et les technologies de traitement des LHF ainsi que les défis associés à leur utilisation.

Résumé: The recovery of waste from the mining industry contributes to the protection of natural resources and the preservation of the environment. In this context, our experimental study aimed to assess the impact of incorporating marble fines in place of limestone fines on the mechanical behaviors of fiber-reinforced sand concrete with organic natural fibers (sheep's wool). The results of this comparison of the various characteristics of fiber-reinforced sand concretes revealed a significant improvement in their apparent density and mechanical properties. However, the introduction of fibers at a rate of 0.2% had a positive impact on uniaxial compressive strength, in contrast to flexural tensile strength at three points.

Résumé: The construction industry plays a pivotal role in economic development. However, it is also ranked third in terms of environmental impact due to its high energy consumption, significant greenhouse gas emissions, and considerable generation of solid waste. The valorization of construction and demolition waste (CD&W) has gained global importance, with a recycling rate exceeding 80% in some countries and the most suitable recycled aggregates (RA) for structural concrete are those obtained from concrete waste. In this context, our work is based on experimental research aimed at studying the effect of incorporating different types of recycled concrete aggregates (RCA), namely sand and gravel, on the rheological, mechanical, and durability properties of conventional concretes. We prepared two series of ternary concrete, target class of C35/45, were made, varying the percentages of substitution by volume from 0% to 100%. In the first series, we replaced alluvial sand with recycled sand, while in the second series, we substituted natural coarse aggregates with recycled coarse aggregates. Through the obtained results, it was observed that the apparent volumetric densities decrease, and the entrapped air increases when recycled aggregates are incorporated, particularly with recycled sand. The characteristic strengths of the different recycled concretes are higher than 35 MPa, even with such high substitution rates, reaching 100%. Nevertheless, the apparent densities, mechanical behaviors, compressive and flexural strengths, as well as elastic moduli, decrease significantly with the increase of recycled sand percentage beyond 50%. The apparent gas permeability of concrete containing 100% recycled sand is 38% higher compared to the reference concrete.

Résumé: The preservation of architectural and cultural heritage goes through the restoration of old buildings, where lime mortar, a traditional material, plays a crucial role thanks to its specific properties and its great compatibility with existing supports. In recent years, research has paid particular attention to the properties of recycled concrete aggregates (CRA) and their integration into cementitious materials. However, CRAs have irregular intrinsic characteristics and weak physico-mechanical properties, thus limiting their frequent use. This experimental study focuses on the effect of the incorporation of recycled concrete sand (RS) on the rheological properties and mechanical behavior of lime-based mortars. Two series of mortars were compared, replacing two types of local natural dune (DS) and quarry (CS) sands with recycled sand at different volume percentages, ranging from 0% to 100%. The results obtained demonstrate that the physical and rheological properties of recycled mortars are influenced when the rate of recycled sand exceeds 30%. At a young age, the mechanical resistances of the various lime-based mortars, evaluated in tension by bending and in simple compression, are practically identical regardless of the mode of curing, either in the open air or protected by plastic. After 28 days of storage, the effect of the superplasticizer, a high water reducer, is quite remarkable for SR rates of 50%. The mechanical behavior of recycled mortars is better than that of control mortars based on natural sand, particularly those from quarries (CS).

Résumé: The proper management of demolition waste is a global priority. One of the solutions proposed is that the environmental impact of the production of aggregates is significant. At the same time, the proper management of demolition waste has become a global priority. One of the proposed solutions is to use this waste in the form of aggregates in self-compacting concrete. During the operation phase of the structures, the concrete may be subject to accidental situations such as fire. Various studies have been carried out to better understand the behavior of different types of concrete: ordinary concrete (OC), self-compacting concrete (SCC) or high performance concrete (HPC) containing natural aggregates. However, little attention has been paid to the behavior of recycled concretes with respect to high temperatures. Our subject of growing interest focuses on the influence of temperature increase on the mechanical properties of self-compacting concrete made from recycled aggregates. This critical study presents a summary of the experimental results: The method of preparation and crushing of recycled aggregates plays a major role in their quality and their intrinsic properties. The loss of mass of concrete subjected to high temperatures depends closely on the nature of the limestone aggregates, however certain forms of silica undergo a significant dimensional change. With temperatures below 300°C and recycled aggregate rates below 30%, SCCs have better temperature resistance than SCCs based on natural aggregates. Some researchers have found that the fine fraction of recycled aggregates, containing more hardened cement mortar, is the most vulnerable in terms of the durability of SCCs and their resistance to high temperatures. Others point out the opposite, because the porosity of recycled aggregates gives them a refractory property. Beyond 400°C up to 900°C, the drop in tensile strength is much faster than that of the compressive strength, and the concrete undergoes significant physico-chemical modifications which strongly influence its microscopy and lead to the appearance of microcracks then macrocracks.

Résumé: L'utilisation de granulats recyclés présente les nouvelles tendances dans la construction comme une alternative aux granulats naturels. Cependant, une absorption d'eau élevée et des propriétés mécaniques pas assez bonnes des granulats recyclés influencent par conséquent, la résistance et la durabilité du béton durci. Pour une tenue pérenne du béton, il est nécessaire d’avoir des exigences de perméabilité à l’eau, au gaz et une résistance à la diffusion d’ions. Ce travail est une contribution expérimentale à l'étude de la durabilité des différentes compositions de bétons ordinaires (naturels/recyclés) avec différentes combinaisons granulaires (sable et gravier). Et, pour se faire réaliser des caractérisations physico-chimiques et mécaniques, des granulats en particulier les recyclés et des bétons ont été menées. Les essais ont été réalisées sur une formulation de béton type : un dosage en ciment constant C=400kg/m3, une même maniabilité du béton frais (Aff= 70±20mm) et une classe de béton cible C25/30. La procédure expérimentale consiste à comparer les résistances mécaniques à long terme, des bétons conservés dans trois types de solutions (eau de robinet, Eau déminéralisée et eau très salée), ainsi que les indicateurs de durabilité les plus déterminants pour ces bétons à savoir : la porosité, la perméabilité et la lixiviation au nitrate d’ammonium avec deux concentrations (faible et forte). Les propriétés physico-mécaniques et chimiques des granulats recyclés (GR) sont inférieures à celles des granulats naturels (GN). Cette étude comparative entre les différents bétons à base des granulats recyclés "issus de béton de démolition" et naturels, montre globalement que ces recyclés possèdent des caractéristiques acceptables vis-à-vis de la durabilité, dont la valorisation des granulats recyclés pour la fabrication des bétons semble une voie prometteuse. MOTS CLES : granulats recyclés, porosité, lixiviation, durabilité.

Résumé: Ce travail est une contribution expérimentale à l'étude de la durabilité des différentes compositions de bétons ordinaires sans adjuvants, à base des granulats naturels et recyclés avec différentes combinaisons granulaires (sable et gravier). Après identification et caractérisation physico-chimiques et mécaniques des granulatsen particulier les recyclés, on a réalisé des essais de durabilité sur des bétons classe cible C25/30 en prenant en considération le même type et dosage du ciment et la même classe de consistance S2.La procédure expérimentale consiste à comparer les résistances mécaniques ainsi que les indicateurs de durabilité les plus déterminants pour ces bétons à savoir : la porosité, la perméabilité et la lixiviation au nitrate d’ammonium. L’étude comparative entre les différentes compositions de bétons recyclés a montré des propriétés physiques et mécaniques acceptables vis-à-vis de la résistance mécanique et de la durabilité. Les granulats recyclés peuvent constituer un matériau de substitution à des granulats naturels. MOTS-CLÉS :granulats recyclés, porosité, lixiviation, durabilité, résistances mécaniques.

Résumé: Aujourd’hui, la valorisation des déchets de construction et de déconstruction (CD&W) est bien développée à travers le monde et l'utilisation des granulats recyclés présente les nouvelles tendances dans la construction moderne comme une alternative aux granulats naturels. Notre travail a pour objectif la valorisation du sable recyclés dans les mortiers bâtards. Cette étude expérimentale est axée sur l’influence de l’incorporation du sable recyclé (SR) de béton sur les comportements rhéologiques et mécaniques des mortiers bâtards (50 % Ciment et 50 % Chaux hydraulique). La formulation des mortiers bâtards est réalisée avec des rapports : Eau/Liant (C+CL) = 0,5 et Sable/Liant = 3,0 ; Les différents mélanges ont été confectionné à base du ciment CEM II 42,5 ; d’un superplastifiant haut réducteur d’eau et en substituant le sable naturel de carrière (SN) par le sable recyclé avec différents pourcentages volumiques de : 0, 20, 30, 40, 50, 75 et 100 %. Les résultats obtenus montrent que les propriétés physico-chimiques du sable recyclé sont inférieures à celles du (SN), dont on a enregistré une absorption d’eau importante (SR), trois fois plus élevée que celle du (SN). L’étude comparative des différentes compositions de mortiers bâtards a montré des comportements physiques et rhéologiques comparables. Cependant, pour un taux de SR inférieur à 50 %, les performances mécaniques des mortiers bâtards recyclés, que ce soit de compression ou de traction par flexion, sont meilleures à celles du mortier témoin à base de sable naturel pour toutes les échéances. Mots-clefs : Environnement, sable recyclé, mortier bâtard, performances mécaniques.