Résumé: Expanded clay aggregates (LECA) are known for their remarkable lightness, allowing structural weight reduction through decreased concrete usage in foundations and load-bearing elements. However, their high water absorption, elevated permeability, and low mechanical strength can hinder their use in structural lightweight concrete. This study proposes an approach to enhance the physico-mechanical properties of LECA by coating them with various cementitious mixtures before incorporating them into lightweight self-compacting concrete (LWSCC). Three coatings were tested: one with ordinary Portland cement (OPC), and two combining cement with sustainable mineral additions — waste glass powder (WGP) and ground granulated slag (GGS). Coatings were applied in one to four successive layers. The results showed that increasing the number of coating layers reduced aggregate water absorption by up to 65 % and improved compressive strength by up to 57 %, which aligns with or slightly exceeds values reported in the literature (e.g., 52–60 % water absorption reduction and 57–200 % strength increase depending on coating composition). Although the slump flow and T500 time slightly declined, the filling ability remained unaffected. Static segregation (SR) and column segregation index (SSI) improved by up to 7 % and 27 %, respectively — improvements that are rarely documented in LECA-based concretes. Compressive strength, flexural strength, and elastic modulus increased by up to 46 %, 28 %, and 215 %, surpassing commonly reported gains (<40 %, <20 %, and <150 %), while maintaining lightweight characteristics (<2000 kg/m³). The best performance was obtained with the GGS-based coating, followed by the WGP-based one. However, the multilayer coating process may raise concerns regarding production time and scalability for industrial applications. Despite these limitations, the findings offer promising prospects for improving structural lightweight concrete using durable and sustainable materials — particularly in applications where mechanical performance and durability are critical.

Résumé: This study investigates the use of demolition waste as recycled coarse aggregates (RCAs) to replace natural coarse aggregates (NCAs), and the use of ground granulated blast slag (GGBS) and limestone filler (LF) as a supplementary cementitious material, in self-compacting concrete (SCC), with proportions of 150 kg/m3 for GGBS and 180 kg/m3 for LF. Various SCC mixtures were prepared with RCA proportions of 0, 25, 50, 75, and 100%, while maintaining fixed dosages of LF and GGBS. Initially, RCA was incorporated in a dry state, followed by a water dosage adjustment for mixtures containing 100% RCA, equivalent to 20 min of RCA absorption. The experimental investigation evaluated the evolution of flow properties through tests such as slump flow, flow time (T500), L-box, sieve stability, fresh density, and air content. The static yield stress and plastic viscosity were also calculated using mathematical models. Additionally, hardened properties, including short-term and long-term compressive strength and capillary water absorption, were assessed. An environmental impact analysis of using demolition waste was conducted, revealing that a total NCA replacement with RCA is viable for both fresh and hardened states, provided that the RCA water absorption is managed and a reactive mineral additive is incorporated. For a 50% replacement of natural aggregates with recycled aggregates, this approach significantly reduces environmental impacts, lowering fossil fuel consumption by up to 35% and greenhouse gas emissions by up to 32%.

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 temperature, 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: Employing ceramic wastes in lime mortars for the restoration of historic buildings has environmental, cultural, social, and economic benefits. This study deals with the possibility of recycling waste glass powder and brick dust in air-lime mortars for restoration purposes. The theatre of the city of Skikda in Algeria was chosen as a case study. To correctly perform the intervention, the main pathologies and the substrate properties were investigated. Different samples of mortars (structural, plaster, external, internal) were taken from the theatre. Their physical and mineralogical properties were determined. Eleven repair mortars were investigated and waste glass powder and brick dust were added to air lime at different substitution rates: 10, 15, 20, 25 and 30%. The local raw materials used and the mortars investigated, were characterised in the laboratory to obtain their mechanical and physical properties. The results were satisfactory and fulfilled the requirements for the application of these mortars for restoration of the theatre, especially concerning mechanical performance. The mortars that were made up by substituting 30% with the two wastes, presented the highest values with an augmentation of 68.7% for mortars with waste glass powder, and 50.5 % for mortars with brick dust. The compressive strength was augmented. Furthermore, it was found that the mortars can also be used for other historic buildings. The two wastes presented pozzolanic activity and improved the mechanical strength of the mortars. From an environmental standpoint, the use of these ceramic wastes offers many advantages, encouraging their re-utilisation and, consequently, reducing landfill disposal.

Résumé: This paper presents an experimental study to study the effect of two mineral additives to limestone filler (LF) on the strength and durability of self-compacting concrete. These are glass powder (GP) from the recovery of glass bottles of the same color and the granulated slag of blast furnaces (GS), a by-product of the steel industry of the El-Hadjar complex of the Annaba region (eastern Algeria). Two series of concrete mixes were prepared with two different resistance classes. Self-compacting concrete (SCC) and selfcompacting high-performance concrete (SCHPC) were evaluated on the basis of mechanical resistance at different times, capillary water absorption, permeability to oxygen, water-accessible porosity, chloride migration, accelerated carbonation and ammonium nitrate leaching. The results of the tests showed that the incorporation of GP and GS improves the mechanical strength of concretes and reduces capillary water absorption, chloride ion diffusion, gas permeability and leaching kinetics compared to LF. However, the GP does not appear to improve the strength of concrete to carbonation, unlike the GS, which has not carbonated. The study also highlighted the enhanced effect of the combination of silica fume (SF), and in particular with the LF and the GP, for their best resistance with the action of carbon dioxide.

Résumé: An experimental study was conducted on the influence of different treatments of date palm fibres on the properties of mortars in both fresh and hardened states. Three types of treatment were discussed: boiling water treatment, sodium hydroxide treatment and a polymer surface treatment based on linseed oil. As a first step, tests of water absorption, setting times and direct tensile strength were performed on single fibres to assess the relevance of the predominant parameter for each treatment. Thereafter, unreinforced mortar and mortars reinforced with raw and treated date palm fibres were made and tested using a flow table test, as well as for porosity accessible to water, three-point bending strength, compressive strength and capillary water absorption. The results for individual fibres show that treatments with a 3-hour boiling of the fibres, a 3% NaOH concentration, and a 1.5% linseed oil/fibre ratio yield the lowest absorption kinetics, the shortest setting times, and the most interesting tensile properties. However, the results for fibrous composites indicate that the workability of mortars reinforced with linseed oil treated fibres was improved compared with raw fibres. In the hardened state, boiling and sodium hydroxide treatments improve the flexural strength of the composites. The same trend was observed for compressive strength. Therefore, the mortar reinforced by fibre treated with linseed oil does not improve the strength and is the most porous. The incorporation of date palm fibres decreases the kinetics of the capillary absorption of mortars compared to unreinforced mortar. The lowest absorption coefficients are obtained after the treatment with linseed oil.

Résumé: In the region of Annaba (Algeria), the colored glass bottles are not sorted or recycled. It should be noted that in some countries like Canada, the recycling of colored glass bottles is not currently viable; the storage would be cheaper [Oxford Brookes University, 2004]. But, the valorization of glass bottles in the concrete could constitute an interesting ecological and economical alternative, allowing the removal of bulky waste and pollutants and their qualification as a new source of building materials. Technically, glass bottles contain significant amounts of alkalis that can cause detrimental effects to concrete in relation to alkali-silica or alkali-aggregate reaction if the glass is used in coarse form. In the other hand, many authors [Chen et al, 2006] agree that the glass causes a beneficial behaviour associated with the pozzolanic reaction when used in powder form. Indeed, our work is a contribution to the valorization of powder glass bottles for substituting the limestone filler traditionally used as an addition in self compacting concrete (SCC). The results obtained show a beneficial behaviour of glass powder on the characteristics, of fresh and hardened self-compacting concrete to a dosage of 30 to 60% compared to the mass of cement.

Résumé: Dans une stratégie de substitution des ressources non renouvelables par des ressources naturelles, renouvelables et à faible impact économique et écologique, les composites cimentaires à base de fibres végétales suscitent un intérêt croissant dans le monde. Quelques chercheurs ont utilisé les fibres végétales comme renforts dans du béton ordinaire, mortier et des matrices argileuses ou à base de plâtre. Par contre, les travaux concernant l’utilisation de fibre végétale dans les bétons autoplaçants (BAP) sont récents et limités. Une question reste souvent posée : les BAP renforcés par des fibres végétales sont-ils aussi résistant et durable que ceux renforcés par des fibres synthétiques ? Il s’agit dans ce travail de comparer un BAP de référence avec fibre de polypropylène a un BAP avec fibres végétales d’Alfa. Les résultats obtenus montrent que les fibres végétales influencent légèrement les caractéristiques des BAP à l’état frais. Cependant, le comportement mécanique des BAP renforcés par des fibres végétales présentent un aspect comparable à celui des BAP avec des fibres de polypropylène.

Résumé: Cette étude, porte sur l’étude de l’influence de la cinétique de relargage des espèces chimique sur la durabilité des matériaux stabilisés/solidifiés (S/S) par liant hydraulique soumis à des milieux chimiquement agressifs. Pour ce faire, deux types de formulations (pâte et mortier) ont été réalisés avec un rapport déchet/ciment (D/C) égal à 25%. Le déchet utilisé provient de l’unité de coutellerie de l’industrie Algérienne. Plusieurs techniques d’analyses et protocoles expérimentaux ont été utilisés, à savoir : la diffraction par rayon X (DRX), le test de lixiviation sur monolithe TLM, et le grattage pour évaluer: l’efficacité du traitement de stabilisation/solidification (S/S) par le ciment CEMI, et la dégradation des matériaux confectionnés sous l’action des sulfates et de l’eau déminéralisée. Les résultats obtenus pour le test TLM pendant 64 jours de relargage montrent l’efficacité du procédé de S/S, par la réduction du potentiel polluant du déchet dans les deux milieux d’étude. Le couplage DRX-grattage a permis la zonation de la partie dégradée des matériaux étudiés, cette dégradation est attribuée à la dissolution et/ou à la précipitation des hydrates. La dégradation du mortier était moins importante par rapport à la pâte de ciment, ceci est dû à l’ajout du sable qui réduit la porosité du matériau. D’après les faibles taux lixiviés, on n’enregistre aucune dégradation notable dans les matériaux étudiés.

Résumé: Self-compacting concretes (SCC) are characterized by high fluidity, put themselves in place without vibration. This property can be obtained by the use of superplasticizer and the increased volume of paste to ensure good dispersion of coarse aggregate, however, to ensure a sufficient volume of paste, there are two possibilities: the first is the increase of cement dosage, inducing an additional cost on the economic and risk of cracking a large exothermy, technically. The second route involves the use of various mineral additives that are usually by-products or waste. The problematic of this work is the enhancement of industrial waste (slag) and household waste (glass bottle) in substitution of limestone filler traditionally used in the SCC. Different formulations are proposed to study the influence of various additions especially, limestone filler, granulated slag and glass powder on the properties of SCC, to fresh and hardened state. The results show a positive effect, of granulated slag and glass powder on rheological and mechanical properties of concretes at rates ranging between 30 and 60% compared to the mass of cement. The optimum dosage is different from an addition to another.