Réutilisation de coproduits coquilliers marins dans des bétons auto-plaçants pour des récifs artificiels

National audienceDue to a need of reusing marine by-products (seashells) in the region of Lower Normandy, self-compacting concretes containing crushed shells replacing the natural aggregates are suitable for the manufacture of complex shaped modules constituting artificial reefs. The objective of this paper is to study the influence of the substitution of natural aggregates by crushed scallop shells on the rheological properties of self-compacting concrete (SCC). For this purpose, four concretes were prepared; one of them used as the control concrete and three concretes incorporating crushed queen scallops at 20, 40 and 60% (substitution of natural aggregates); to measure the properties of mobility, the filling capacity, the viscosity, the cohesion, the risk of blockage and segregation, and the mechanical properties.En raison d'une nécessité de valorisation de coproduits coquilliers marins dans la région de Basse-Normandie, France, des bétons fluides contenant des coquilles concassées en remplacement des granulats naturels ont été incorporées pour la fabrication des modules de formes complexes constituant les récifs artificiels. L'objectif de ces travaux de recherche est l'étude de l'influence de la substitution des granulats naturels par des coquilles de pétoncle concassées sur les propriétés rhéologiques d'un béton auto-plaçant (BAP). A cet égard, quatre bétons ont été préparés ; un béton témoin et trois bétons dont sa matrice granulaire a été remplacée par des pétoncles concassées à 20, 40 et 60% afin de mesurer les propriétés de mobilité, la capacité de remplissage, la viscosité, la cohésion, le risque de blocage et de ségrégation ainsi que les propriétés mécaniques

Alkali activated mortars formulation optimized by an experimental design

International audienceThe worksites of "Grand-Paris" will generate high amounts of excavated lands, without few recovery routes. One of them could be to use those excavated lands into alkali activated materials, based on ground granulated blast furnace slag. The study herein presented concerns the feasibility of using various untreated soils originating from Normandy (France) as the granular skeleton in alkaline activated granulated blast furnace slag-based mortars. The use of experimental designs allowed to optimize the binding phase, by varying the composition of the activation solution, for sand and slag-based mortars. The impact of hardened properties of materials was thus studied

Concrete Durability Probed Using Compressive Strength, Chloride Penetration and Porosity Measurements on CEMII and CEMV Concretes Incorporating Mollusc Shell Spares in Artificial and Natural Seawaters

The purpose of this study is to improve the recruitment of flat oyster larvae, an endangered species, by means of a specific marine infrastructure made of concrete. This work aims to develop and optimize concrete formulations by varying the type of cement and introducing shellfish by-products into their composition and determine which concrete formulation is the most sustainable to marine organism colonization. Indeed, it is essential to obtain a sustainable concrete submitted to aggressive marine environment (chloride ions diffusion and bio-colonisation). Four concrete formulations were tested with two types of cements (CEMII and CEMV) and with or without the incorporation of shell aggregates. The durability of these materials was tested after 3 months of immersion in the Rance of Dinard (France). It appears from this study that the CEMII concrete exhibits a good mechanical resistance independently of the presence of shell, after immersion in situ. This concrete also shows better resistance to chloride ions diffusion than CEMV. However, CEMV possess larger compressive strengths than CEMII, and mollusc shells incorporation does not decrease this strength as much as for CEMII. Shell incorporation in the concretes has an effect on strength, chloride penetration and porosity which depend on the used cement and seawater

Artificial reefs built by 3D printing: systematisation in the design, material selection and fabrication

The recovery of degraded marine coasts and the improvement of natural habitats are current issues of vital importance for the development of life, both marine and terrestrial. In this sense, the immersion of artificial reefs (ARs) in the marine environment is a way to stimulate the recovery of these damaged ecosystems. But it is necessary to have a multidisciplinary approach that analyses the materials, designs and construction process of artificial reefs in order to understand their true impact on the environment. For this reason, this paper presents the manufacture of artificial reefs by 3D printing, proposing designs with a combination of prismatic and random shapes, with different external overhangs as well as inner holes. For the definition of the artificial reef designs, criteria provided by marine biologists and the results obtained from a numerical simulation with ANSYS were taken into account, with which the stability of the artificial reefs on the seabed was analysed. Three dosages of cement mortars and three dosages of geopolymer mortars were studied as impression materials. The studies included determination of the rheological properties of the mortars, to define the printability, determination of the cost of the materials used, and determination of the mechanical strength and biological receptivity in prismatic specimens that were immersed in the sea for 3 months. To evaluate the environmental impact of the materials used in the production of the mortars, a Life Cycle Assessment (LCA) was carried out. In order to choose the mortars that encompassed the best properties studied, Multi-Criteria Decision Making (MCDM) was applied and the two best mortars were used for the manufacture of the artificial reefs. Finally, the advantages and disadvantages of the 3D printing process used were analysed. The results of the studies carried out in this research show that cement mortars have better characteristics for artificial reef applications using 3D printing, and that the technique applied for the manufacture of the artificial reefs allowed the digital models to be faithfully reproduced.This work has been co-financed by the European Regional Development Fund through the Interreg Atlantic Area Programme, under the project “Artificial Reef 3D Printing for Atlantic Area - 3DPARE” (EAPA_174/2016). Besides, the authors want to thank the following companies for their contribution: Solvay, for supplying the fly ash and sodium hydroxide; BASF, for providing the additives used in the research; Abonomar S.L., for providing the seashells sand; FCC ámbito, for providing the crushed recycled glass and Grupo Cementos Portland Valderribas (Mataporquera plant) for providing the cement

Reducing energy consumption of prefabricated building elements and lowering the environmental impact of concrete

International audienc

Effect of several parameters on non-autoclaved aerated concrete: use of recycling waste perlite

This article presents the results of an experimental study on a new protocol to create a non-autoclaved cellular concrete containing a partial substitution of sand by an equivalent volume of pure perlite and perlite waste. The development of the experimental protocol was performed based on a series of steps to control each parameter that influences this swelling procedure (temperature, water content, duration, containment, restricted swelling and filling height). Each parameter has been the subject of feasibility test, process and thermal validation analysis. The perlite pure or waste used for volume substitution (30%/30%) of sand was characterised by a lower density, which allowed the concrete to swell under non-autoclaved conditions. Each element were tested to evaluate their influence on thermal insulation properties. Presence of recycled product decreased the mechanical strength but promoted thermal insulation properties. An optimisation of the formulation is needed to keep a high porosity but obtained a better mechanical strength. With an increase of 2% of cement we can increase the mechanical strength value of 21%. Based on the investigated formulations, 100% expanded material with a thermal conductivity of 0.176 W/m.K was achieved. As such, the non-autoclaved swelling protocol facilitated the development of insulation material based on recycled products

Effect of several parameters on non-autoclaved aerated concrete: use of recycling waste perlite

International audienc

Effects of Wetting and Drying Cycles on Microstructure Change and Mechanical Properties of Coconut Fibre-Reinforced Mortar

International audienceNatural fibre-reinforced cementitious composites are commonly used as outer construction materials. They usually suffer weather as a result of being expose to various types of climates. In this study, a series of experimental tests were carried out to investigate the deterioration mechanism and mechanical properties of mortars incorporating coconut fibres due to repeated wetting and drying. The results indicated that although the compressive strength was found to increase after the first cycle, both compressive and flexural strengths underwent a significant decrease in the fifth cycle. In addition, at high temperatures, mortar matrixes retain their stable structure, according to the results of TGA analysis. When wetting and drying curing was applied, there was a significant degradation of fibres in the mortar

Optimization of non-autoclaved aerated insulating foam using bio-based materials

International audienc

Projet 3DPARE : Impression 3D de récifs artificiels pour l'espace Atlantique

International audienceLe projet 3DPARE (3D Printing Artificial REef) a pour objectif de développer des récifs artificiels innovants pour la gestion durable des écosystèmes marins sur les côtes Atlantique. Un récif artificiel est défini comme étant « une structure immergée volontairement, placée sur des fonds marins pour imiter et reproduire les fonctions d'un récif naturel telles que la protection, la régénération, la concentration ou l'augmentation des populations d'organismes marins » [1]. Ces récifs sont mis en place pour réparer, protéger et/ou restaurer des écosystèmes qui se voient détériorés depuis plusieurs décennies par l'accroissement global de la température, la hausse du CO2 atmosphérique ou encore l'acidification des océans [2]. Cependant, les technologies utilisées pour la création de récifs artificiels n'ont pas été optimisées pour le cadre européen