Experimental study on flexural creep of self-compacting concrete reinforced with vegetable and synthetic fibers

Abstract This article evaluates the impact of different fiber types on the flexural creep of self-compacting concretes (SCC). The study focuses on the effects of vegetable fibers (Hemp, [H] and Dis [D]) and synthetic fibers (Polypropylene [P]) on SCC. To assess the SCC, various tests such as spreading, J Ring, compressive strength, and flexural strength are conducted. The authors developed a test configuration and methodology to subject beams measuring 120 cm in length to sustained flexural stresses for 200 days. Two curing modes of the beams are also studied: total creep (beams exposed to air) and endogenous creep (beams protected from air). Moreover, the plant fibers were previously subjected to two treatments separately; the first involves immersing them in a 5% alkaline solution of NaOH (HN and DN) and the second in a solution of the polymer styrene-butadiene rubber (SBR) (HS and DS). The findings show that the treatment of vegetable fibers by SBR reveals high mechanical properties as well as a good capacity for endogenous and total creep. SCC-DS shows an increase in flexural strength of 9% and 13% with a decrease in total creep of 4% and 16% compared to SCC without fiber and SCC-DN, respectively. These results are promising for further reflection on a large scale to explore the issue of strengthening SCC with treated vegetable fibers

Contribution à l'étude de la durabilité et les performances des bétons autoplaçants (fibres végétales, milieu agressif, formulation, modélisation

Ces dernières années ont vu un regain d’intérêt pour, des fibres végétales. En effet, ces fibres peuvent représenter une alternative aux fibres traditionnelles utilisées dans les matériaux de construction, telles que les fibres polypropylènes. Le développement durable exige des matériaux respectueux de l’environnement donc des matériaux naturels. En ce sens, les fibres végétales utilisées comme renfort pour les matériaux cimentaires constituent une option très intéressante pour l’industrie de la construction. Ainsi, notre travail de recherche se compose de deux parties. La première partie concerne l’étude de l’influence de la nature des fibres sur les caractéristiques à court et à long terme du béton autoplaçant. La seconde partie est dédiée à une approfondie sur l’effet des fibres végétales sur les mortiers à base de metakaolin. Dans la première partie sept mélanges de béton autoplaçant ont été confectionnés à base de 6 types de fibre de nature différente (chanvre, chènevotte, Palmier dattier, Alfa, Dis et polypropylène); les bétons sont testés à différents essais expérimentaux (Résistance à la compression, à la flexion, retrait, fluage, comportement au feu et attaque sulfatique). Dans la deuxième partie six mélanges de mortier à base de metakaolin ont été effectuées avec les mêmes fibres précédentes sauf le chènevotte. Ces fibres ont été préalablement traitées avec de l’hydroxyde de calcium. Le comportement des mortiers à base de ces différentes fibres a été étudié vis-à-vis de plusieurs phénomènes : conductivité thermique, carbonatation, cycle gèle-dégel et comportement à l’élévation de la température. Une analyse microstructurale a été realisée pour mieux comprendre ces phénomènes. Les résultats obtenus montrent que l’incorporation des fibres végétales comme renfort écologique dans les BAP présente des caractéristiques à l'état frais et à l'état durci comparable à celles d’un BAP témoin sans fibres. Dans cette étude on confirme que la réalisation des BAP avec fibres végétales est possible. Néanmoins, ces fibres doivent être préalablement traitées pour un meilleur comportement, notamment vis-à-vis de la durabilité

Enhancement of physical and mechanical properties of polymer-based repair mortars using SBR (Styrene-Butadiene Rubber) and glass fiber reinforcement: Experimental and numerical investigation

This article investigates the mechanical properties of cementitious repair mortars modified with styrene-butadiene rubber (SBR) at dosages of 5% and 10% by weight of cement. It includes an analysis of flexural strength (FS) and compressive strength (CS), as well as transport properties such as total shrinkage (SR) and water absorption (WA). Glass fibers (GF) were added to these mortars at rates of 0.1%, 0.3%, and 0.5% of the total volume to reinforce them. A factorial design was employed in numerical modeling to study the effects of different SBR and GF levels on the physical and mechanical properties of the repair mortars. An analysis of variance (ANOVA) was conducted to determine the significance of the factors and their interactions on the selected responses. Digital Image Correlation (DIC), using GOM software, was used to measure and quantify deformations and movements. The findings reveal that polymer mortars reinforced with glass fibers exhibit greater resistance to bending and compression than polymer mortars without fibers. Furthermore, fiberglass-reinforced mortars demonstrate good dimensional stability over time with respect to total shrinkage. Moreover, the developed mathematical models yield efficient prediction equations for FS, CS, SR, and WA by considering SBR content and fiberglass levels. DIC provides a highly effective numerical representation of stressed areas, locations of crack initiation, fracture mechanisms, and crack propagation. The repair mortar exhibits strong adhesion to concrete exposed to high temperatures

Measures of Agreement Between Computation Programs and Experiment: The Case of Beams with Circular Cuts in their Webs

In the field of metal construction, cellular beams represent an attractive solution to meeting the various technical and economic constraints, especially for large-span buildings. In particular, they allow components linked to the construction to pass through their openings (ventilation ducts, electrical threads, etc.) and thus contribute to significantly reducing the thickness of the floors. However, the use of such beams requires special attention to comply with the regulations in force, in order to guarantee stability and behavior in line with the challenge of preserving the structures. This article focuses on the analysis of the measures of agreement between experiment and computation programs (strength of materials, Robot structures, and Inflexion-EF) results of the beams with circular cuts in their webs (IPE A 100), supported simply and subjected to a concentrated load. The experimental results show that the vertical displacement resulting from transverse compression is induced by various factors: length, cuts in their webs, location of the load, and stiffening of the beams. The comparison of experimental and theoretical results demonstrates the importance of experimental tests in validating theoretical results

Aggregate Type Influence on Microstructural Behavior of Concrete Exposed to Elevated Temperature

Exposure of concrete to high temperatures affects its mechanical properties by reducing the compressive strength, bending… etc. Factors reducing these properties have been focused on by several studies over the years, producing conflicting results. This article interested an important factor, that is the type of aggregates. For this, an experimental study on the behavior of concrete based on different types of aggregates: calcareous, siliceous and silico-calcareous subjected to high temperatures. In addition, the particle size distribution of the aggregates was chosen to be almost identical so that the latter does not affect the behavior of the concrete. Aggregates and concrete samples were subjected to a heating/cooling cycle of 300, 600 and 800°C at a speed of 1°C/ min. The mechanical and physical properties of concrete before and after exposure to high temperatures were studied. In addition, a microstructural study using a scanning electron microscope and a mercury porosimeter was performed. Thus, a comparative study between various researches on the mechanical properties of concrete exposed to high temperatures containing different types of aggregates was carried out. The compressive strength test results showed that the concrete based on siliceous aggregates (C-S) has better mechanical performance up to 300°C. However, above 300°C, the compressive strength decreases faster compared to calcareous-based concrete (C-C). According to the mercury porosimeter test, at 600°C, C-SC and C-S concretes have the highest number of pores compared to C-C concretes. The microstructure of concrete at high temperatures was influenced mainly by the aggregate’s types and the paste-aggregate transition zone. This study reinforces the importance of standardizing test procedures related to the properties of concrete in a fire situation so that all the results obtained are reproducible and applicable in other research