Influence du type d'addition minérale sur le comportement physico-mécanique et sur la durabilité des bétons autoplaçants

En raison des spécificités relatives à la formulation des bétons autoplaçants (BAP) et en particulier ce qui concerne leur volume élevé en pâte et la présence d ajouts minéraux en grande quantité, leur comportement à l état frais et à l état durci ainsi que leur durabilité sont fortement influencés par ces deux paramètres. Ce travail de recherche vise à apporter une contribution à la valorisation de la pouzzolane naturelle de Béni-Saf (Algérie) en tant qu addition minérale dans la composition de bétons autoplaçants économiques. Il s agit de comparer l influence de la nature des ajouts minéraux (pouzzolane naturelle, cendre volante et filler calcaire) sur les caractéristiques physicomécaniques et sur la durabilité de ces bétons à court terme (28 jours), à moyen terme (90 jours) et à long terme (360 jours). Au total, douze formulations ont été étudiées, elles couvrent trois différentes classes de résistances (30 MPa, 50 MPa et 70 MPa) et quatre types de bétons : un béton ordinaire vibré (BOV), un BAP à base de pouzzolanes naturelles (BAP PZ), un BAP à base de fillers calcaires (BAP FC) et un BAP à base de cendres volantes (BAP CV). Les résultats de la résistance à la compression obtenus sont très proches selon la classe de résistance pour les trois additions minérales utilisées dans les BAP. Les résultats des essais d arrachement (pull-out test), de l absorption capillaire, de la porosité accessible à l eau et au mercure, du coefficient de diffusion des ions chlorures, de la perméabilité à l hélium, de l attaque acide (HCl et H2SO4) et de l attaque sulfatique Na2SO4, montrent que la nature de l addition minérale dans les BAP influe considérablement les propriétés physico-mécaniques et la durabilité de ces bétons. Les BAP contenant de la pouzzolane naturelle (BAP PZ) représentent non seulement un intérêt économique, mais aussi des performances très comparables à celles obtenues sur des BAP à base de cendres volantes (BAP CV) et bien meilleures que celles sur des BAP formulés avec du filler calcaire. Par ailleurs, Les BAP PZ et les BAP CV présentent des valeurs de retrait acceptables mais légèrement supérieures à celles des autres bétons.Because of the specificities of self-compacting concrete (SCC), especially regarding their high volume paste content and the presence of large amounts of mineral admixtures, the behavior in fresh and hardened state and the durability of these concretes are strongly influenced by these two parameters. This research aims to contribute to the valorization of the natural pozzolan of Beni Saf (Algeria) as a mineral admixture on the composition of an economic self-compacting concrete. The influence of the nature of different mineral admixtures (natural pozzolan, fly ash and limestone filler) on the physical, mechanical behavior and durability of these concretes in the short-term (28 days), medium-term (90 days) and long-term (360 days) were investigated. In total, twelve formulations were studied, thus covering three various strength classes (30 MPa, 50 MPa, and 70 MPa), as well as four types of concrete: ordinary vibrated concrete (OVC), SCC with limestone filler addition (SCC LF), SCC with natural pozzolan (SCC PZ), and SCC with fly ash (SCC FA). The results obtained of the compressive strength are very close by strength classes for the three mineral admixtures used in the SCC. The results of the different following tests : pull-out test, capillary absorption, accessible water and mercury porosity, chloride ion diffusion, helium permeability, carbonation, acids attack (HCl and H2SO4) and sulfate attack (Na2SO4), show that the nature of the mineral admixture influence greatly the physico-mechanical behavior and durability of the SCC. Also, shrinkage measurements and analysis show that SCC PZ and SCC FA present acceptable values slightly higher than those of other concretes. The SCC containing natural pozzolan represents not only an economic SCC but also performances quite comparables to those obtained on SCC containing fly ash and better than those of SCC made with limestone filler.RENNES-INSA (352382210) / SudocSudocFranceF

Nano-tailored multi-functional cementitious composites

WOS: 000509629400050This paper explores the effects of single and binary use of nano-additions on the self-sensing and self-healing efficiencies of cementitious composites in achieving a material that combines high mechanical and multifunctional performances. The researchers studied three nano-tailored cementitious compositions incorporating nano-silica (NS), multi-walled carbon nanotubes (CNT) and binary NS/CNT, as well as control composites prepared without nano-additions. The study included compressive strength testing on sound specimens and an evaluation of combined self-sensing/self-healing capabilities with electrical resistivity (ER) measurements conducted before and after preloading and during the self-healing recovery stage. Recovery rates were also evaluated via crack width measurements recorded by video microscope and compared to ER testing results. To account for different self-healing products, microstructural characterization was performed on healed cracks using scanning electron microscopy coupled with EDX (SEM/EDX) and thermo-gravimetric (TG/DTG) analyses. Results show that while the single use of CNT can promote self-sensing and self-healing properties, using binary NS/CNT can significantly enhance these performances. The density and amounts of C-S-H and CaCO3 in healed cracks increased with the addition of nano-materials, especially for the binary NS/CNT.Scientific and Technical Research Council (TUBITAK) of TurkeyTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [114R043, 117M954]The authors gratefully acknowledge the financial assistance of the Scientific and Technical Research Council (TUBITAK) of Turkey provided under projects: 114R043 and 117M954

Influence of Mineral Admixtures on the Permeation Properties of Self-Compacting Concrete at Different Ages

International audienceDue to its specific properties, the study of self-compacting concrete (SCC) represents an area of research that has strong potential for development. However, in spite of the interest of researchers in this new material, SCC has not yet gained universal acceptance as a construction material, and its application remains limited. The development of an economical SCC with interesting properties in the fresh and hardened state is important for the acceptance of such a concrete. Algerian natural source Pozzolan is rarely used in SCC due to the absence of any thorough study of its properties. This study investigates the permeation properties of SCC mixtures made with this Algerian natural Pozzolan, compared with conventional vibrated concrete and other SCC mixtures containing fly ash or limestone filler. Additionally, the correlations between chloride diffusion and sorptivity, and between apparent gas permeability and chloride diffusion, were investigated. Results indicate that, despite its economic benefits, SCC incorporating natural Pozzolan presents very low permeation properties (for example: lower migration coefficients compared to the SCC mixtures with limestone filler or ordinary vibrated concrete (difference > 50 % for results of the 30 MPa strength class). The relation between chloride diffusion and sorptivity, and between apparent gas permeability and chloride diffusion, is also confirmed

Advanced engineered cementitious composites with combined self-sensing and self-healing functionalities

International audienc

Assessment of the long-term performance of SCC incorporating different mineral admixtures in a magnesium sulphate environment

International audienceThe effects of mineral admixture type on the behaviour of self-consolidating concrete (SCC) in magnesium sulphate environments were investigated over the course of four years of exposure. Three mineral admixtures (limestone filler, fly ash and natural pozzolan) representing a wide range of compositions were used in the study. Twelve formulations covering three strength classes (30, 50 and 70 MPa) and four concrete mixtures were studied. Mass loss with physical deterioration, and dimensional and compressive strength changes due to magnesium sulphate attack were determined through microstructural analysis. The sulphate profiles of sulphur, magnesium, silicon, calcium and aluminium elements were also quantified through analyses of the samples. A complementary analysis by phase assemblages was performed on the degraded layers of concrete specimens. These test results indicate that the mineral admixture type greatly affects the durability performance of SCC under magnesium sulphate exposure. Among the tested mineral admixtures, natural pozzolan showed better long-term durability performance in the magnesium sulphate environment. The interaction between vibrated concrete and SCC is related to the nature of the mineral admixtures

Effect of mineral admixture on resistance to sulphuric and hydrochloric acid attacks in selfcompacting concrete

International audienceThis paper presents a detailed experimental investigation of the acid resistance of economical self-compacting concrete (SCC) prepared with natural pozzolan, immersed for up to 12 weeks in sulphuric acid (H2SO4) and hydrochloric acid (HCl) solutions. The results are compared with those from a control concrete and other SCCs prepared with fly ash and limestone filler. The different factors considered in this study were the effect of mineral admixture type and the strength classes (30, 50, and 70 MPa) of the concrete specimens. In total, 12 formulations were tested. Mass and compressive strength losses are the main properties investigated. Scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses were used to better understand the kinetics of deterioration of each type of concrete. The results show the positive influence of natural pozzolan on the behaviour of SCC under both sulphuric and hydrochloric acid mediums

Influence du type d'addition minérale sur les propriétés de transfert des Bétons AutoPlaçants

International audienceLa formulation des bétons autoplaçants (BAP) présen te certaines spécificités dont un volume élevé de pâte et une quantité importante d'ajouts m inéraux. Ces deux paramètres influencent sensiblement les propriétés de transfert de ces bét ons. Dans ce travail, nous avons étudié l'influence de l a nature et du pourcentage de plusieurs additions minérales sur certaines propriétés de tra nsfert (la diffusion des ions chlore et la perméabilité au gaz) des BAP. Trois différentes add itions minérales ont été testées : des fillers calcaires, de la pouzzolane naturelle et des cendre s volantes. Ensuite, nous avons cherché une probable relation analytique entre ces propriétés e t la résistance à la compression de ces bétons. Au total, douze formulations ont été étudiées, elle s couvrent trois différentes classes de résistances (30 MPa, 50 MPa et 70 MPa) et quatre ty pes de bétons: un béton ordinaire vibré, un BAP à base de pouzzolanes naturelles, un BAP à base de fillers calcaires et un BAP à base de cendres volantes. Les résultats montrent que la nature de l'addition minérale dans les BAP influe considérablement sur les propriétés de transferts de ces bétons. Apr ès 28, 90 et 360 jours de cure, les BAP contenant de la pouzzolane naturelle représentent d es performances très comparables à celles obtenues sur des BAP à base de cendres volantes et bien meilleures que celles obtenues sur des BAP formulés avec du filler calcaire. Indépendammen t du type d'addition minérale, les résultats confirment l'existence d'une forte corrélation entr e le développement de la résistance à la compression et les propriétés de transferts des BAP

Influence Of Natural Pozzolan On The Behavior Of Self-Compacting Concrete Under Sulphuric And Hydrochloric Acid Attacks, Comparative Study

International audienceAcidic attack is a topic of increasing significance, owing to the spread of damage to concrete structures in both urban and industrial areas. Mineral addition type is an important factor affecting performance of Self-Compacting Concrete (SCC) in an aggressive environment. Pozzolan from natural sources in Algeria is rarely used in SCC due to the absence of a thorough study of its properties. The goal of this study was to compare the hydrochloric and sulphuric acid behaviors of a SCC-containing Algerian natural pozzolan with SCC-containing fly ash and limestone filler additions. For this purpose, twelve formulations were prepared with three different strength classes (30, 50, and 70 MPa). After 28 days of curing, the samples were immersed in hydrochloric sulfuric acid solutions for a period of 12 weeks. The changes in mass loss and compressive strength loss for each acid solution within the test period were recorded. The Scanning Electron Microscope (SEM) and XRD analysis were used to better understand the mechanism of deterioration of each type of concrete. In spite of their economical properties, the results confirm that the use of Algerian natural pozzolan contributes to the improvement of resistance of SCC under sulphuric and hydrochloric acid attack

Use of recycled glass powder to improve the performance properties of high volume fly ash-engineered cementitious composites

International audienc

Characterization of the degradation of self-compacting concretes in sodium sulfate environment: Influence of different mineral admixtures

International audienceThe effects of the type of mineral addition on the behavior of SCCs in sodium sulfate environments were studied. Three strength classes (30 MPa, 50 MPa and 70 MPa) and three different mineral additions were investigated: limestone filler, fly ash and natural pozzolan. The results were compared to those of vibrated concretes. Compressive strength, mass and dimensional changes dues to sodium sulfate attack were determined. The microstructure was studied using SEM-EDS and XRD analysis. For 720 days of immersion in 5% Na2SO 4 solution, the penetration depth of sulfate in different samples was quantified using SEM-EDS. The results were consistent with those of XRD analysis. This study shows the benefic effect of the incorporation of a natural pozzolan as a mineral admixture in SCC on the resistance of these concretes in sodium sulfate medium. SCCs with natural pozzolan present characteristics very comparable with those of SCC mixtures with fly ash. It appears that the use of vibrated concretes or SCC with limestone filler, especially with low compressive strength, in a rich sodium sulfate environment is not recommended