Optimization of bricks production by earth hypercompaction prior to firing

This paper presents an innovative method for the production of masonry bricks, which combines earth compaction and quick firing at low temperatures. Earth bricks were manufactured according to three different methods, i.e. extrusion, standard Proctor compaction and hypercompaction to 100 MPa. All bricks were fired inside an electrical furnace by rising the temperature at a quick rate of about 9 °C per minute to 280, 455, 640, 825 and 1000 °C, after which the furnace was turned off and left to cool to the atmosphere with the brick inside it. These firing temperatures and times are significantly lower than those employed for the manufacture of commercial bricks, which are typically exposed to a maximum of 1100 °C for at least 10 hours (Brick Industry Association, 2006). A testing campaign was performed to investigate the effect of quick firing on the porosity, strength, water durability and moisture buffering capacity of the different bricks. Quick firing of hypercompacted bricks at moderate temperatures, between 455 and 640 °C, is enough to attain very high levels of compressive strength, between 29 and 34 MPa, with a good to excellent moisture buffering capacity. These properties are better than those of commercially available bricks. The strength of hypercompacted bricks further increases to 53 MPa, a value similar to that of high-strength concrete, after quick firing at 825 °C. Earth densification prior to thermal treatment therefore improves material performance while enabling a significant reduction of firing temperatures and times compared to current bricks production methods

Experimental contribution to the study of the physic-mechanical behavior and durability of high-performance concretes based on ternary binder (cement, silica fume and granulated blast furnace slag)

Le béton à hautes performances (BHP) est un béton innovant largement utilisé dans la construction moderne. De nouvelles techniques de formulation et de conception du HPC ont permis d'obtenir des performances mécaniques et une durabilité remarquables par rapport au béton conventionnel. Les principaux avantages du HPC sont liés à sa faible porosité, sa très haute résistance mécanique et son excellente durabilité. La facilité d'application du HPC est obtenue par l'utilisation combinée de superplastifiant et d'ajout de minéraux, ce qui se traduit par une augmentation significative de la résistance à la compression tout en améliorant la maniabilité et la durabilité. L'utilisation d'un liant ternaire (ciment, fumée de silice et laitier granulé de haut fourneau broyé) dans la fabrication du HPC est une nouvelle avancée dans la construction durable qui offre des avantages économiques, techniques et écologiques. L'objectif de ce travail de recherche était d'améliorer les propriétés physico-mécaniques du HPC à base de liant ternaire en étudiant l'influence du remplacement du ciment par du laitier granulé et des fumées de silice. Les résultats des tests mécaniques montrent que les performances du HPC réalisé avec ces liants ternaires sont similaires au HPC témoin sans laitier granulé. Enfin, il est conclu que l'utilisation de tels liants est très bénéfique pour diminuer les problèmes environnementaux et améliorer la durabilité du HPC

Fire spalling sensitivity of concrete made with recycled concrete aggregates (RCA)

The fire spalling of concrete is a complex phenomenon, which can affect the integrity of the structures during a fire. This thermal instability is associated with a complex coupled chemo-thermo-hydro-mechanical mechanism and it can be influenced by many factors, related to material (e.g. per- meability, porosity and water content), geometry (e.g. shape and size) and environmental parameters (e.g. mechanical load and heating rate). Concrete made with recycled concrete aggregates presents higher porosity, higher water content and different interfaces between aggregates and mortar. All these aspects can lead to a different behaviour under fire exposure, including the spalling risk of these sustainable concretes. The main objective of this paper is to analyse the influence of the use of recycled concrete aggregates on the spalling risk of concrete. In this paper, concrete prisms with different replacement rates of recycled coarse aggregates (0 up to 100%) were exposed to a standard fire curve (ISO 834-1) with a constant uniaxial compression load. After heating, samples surfaces were evaluated by means of digital photogrammetry. Results showed that concrete with RCA is sensitive to explosive spalling. All replacement rates presented higher degree of spalling than concrete made with natural aggregates

RILEM Contribution to Earthen Building

Publisher Copyright: © The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.Earth as building materials and earthen building products are important for the conservation and rehabilitation of historic and vernacular construction, but also to build new eco-efficient buildings. Earth is not standardized as for other more common construction materials. For earthen products to be applied, depending on the building technologies used and the architectural and engineering design, their performance must be known. Therefore, there is a need to define standardized test procedures, so that performance results can be validated and compared. Within the International Union of Laboratories and Experts in Construction Materials, Systems and Structures (RILEM) an effort has been made, so that earthen materials and products can be addressed, and test methods can be discussed, optimised and defined. This article presents the evolution within RILEM of earth as building material, earthen building products and elements, details difficulties, but also the achievements reached so far. It intends to spread the work now being done, namely within RILEM Technical Committees BEC, MAE and PEM, so that a larger number of professionals can contribute and profit from results achieved.authorsversionpublishe

INFLUENCE DE LA DÉCALCIFICATION DE MATERIAUX CIMENTAIRES SUR LES PROPRIÉTÉS DE TRANSFERT : APPLICATION AU STOCKAGE PROFOND DE DÉCHETS RADIOACTIFS

Thèse préparée en cotutelle entre l'UPS de Toulouse au LMDC et l'Université de Sherbrooke au Québec au LMRGA pour l'obtention du doctorat et du Ph.D.Cementitious materials have been selected to compose the engineering barrier system (EBS) of the french radioactive waste deep repository, because of concrete physico-chemical properties: the hydrates of the cementitious matrix and the pH of the pore solution contribute to radionuclides retention; furthermore the compactness of these materials limits elements transport. The confinement capacity of the system has to be assessed while a period at least equivalent to waste activity (up to 100.000 years). His durability was sustained by the evolution of transfer properties in accordance with cementitious materials decalcification, alteration that expresses structure long-term behavior. Then, two degradation modes were carried out, taking into account the different physical and chemical solicitations imposed by the host formation.The first mode, a static one, was an accelerated decalcification test using nitrate ammonium solution. It replicates the EBS alteration dues to underground water. Degradation kinetic was estimated by the amount of calcium leached and the measurement of the calcium hydroxide dissolution front. To evaluate the decalcification impact, samples were characterized before and after degradation in term of microstructure (porosity, pores size distribution) and of transfer properties (diffusivity, gas and water permeability).The influence of cement nature (ordinary Portland cement, blended cement) and aggregates type (lime or siliceous) was observed: experiments were repeated on different mortars mixes.On this occasion, an essential reflection on this test metrology was led.The second mode, a dynamical degradation, was performed with an environmental permeameter. It recreates the EBS solicitations ensured during the resaturation period, distinguished by the hydraulic pressure imposed by the geologic layer and the waste exothermicity.This apparatus, based on triaxial cell functioning, allows applying on samples pressure drop between 2 and 10 MPa and temperature from 20 to 80°C. Water permeability evolution relating to experimental parameters, uncoupled or coupled, was relied to mortars microstructural modifications.Les matériaux cimentaires ont été retenus afin de composer la barrière ouvragée du site français de stockage des déchets nucléaires en formation géologique profonde. Ce choix se justifie par les capacités physico-chimiques propres aux bétons : les hydrates de la matrice cimentaire (CSH) et le pH de sa solution interstitielle contribuent à la rétention des radionucléides ; d'autre part la compacité de ces matériaux limite le transport d'éléments. Il convient de s'assurer de la pérennité de cette structure pendant une durée au moins égale à celle de la vie des déchets (jusqu'à 100 000 ans). Sa durabilité a été éprouvée par l'évolution des propriétés de transfert en fonction de la décalcification de matériaux cimentaires, altération traduisant le vieillissement de l'ouvrage. Deux modes de dégradation ont ainsi été appliqués tenant compte des différentes interactions physico-chimiques induites par la formation hôte. Le premier, de type statique, a consisté en une décalcification accélérée par le nitrate d'ammonium. Il simule l'altération de la barrière ouvragée par les eaux souterraines. La cinétique de la dégradation a été estimée par le suivi du calcium lixivié et l'avancée du front de dissolution de l'hydroxyde de calcium.Pour évaluer l'impact de la décalcification, les échantillons ont été caractérisés à l'état sain puis dégradé, en termes de microstructure (porosité, distribution porosimétrique) et de propriétés de transfert (diffusivité, perméabilité au gaz et à l'eau). L'influence de la nature du liant (CEM I et CEM V/A) et des granulats (calcaires et siliceux) a été observée en répétant les essais sur différentes formulations de mortiers.A cette occasion, une importante réflexion sur la métrologie de cet essai a été menée.Le deuxième mode de dégradation, dynamique, a été réalisé par un perméamètre environnemental. Il recrée les sollicitations subies par l'ouvrage lors de sa phase de resaturation post-fermeture (pression hydraulique imposée par la couche géologique et exothermicité des déchets).Cet appareillage, basé sur le principe d'une cellule triaxiale, a permis de fixer un gradient de pression entre 2 et 10 MPa et une température de 20 à 80°C. La variation de la perméabilité à l'eau en fonction de ces deux paramètres expérimentaux, découplés et couplés, a été mesurée et reliée aux modifications microstructurales des échantillons. Mots clés : décalcification, CEM I, CEM V/A, diffusivité, perméabilité au gaz, perméabilité à l'eau, porosimétrie mercure, dégradation par nitrate d'ammonium, perméamètre environnemental, gradient de pression, température, stockage nucléaire souterrain

Effect of stabilisation on mechanical properties, moisture buffering and water durability of hypercompacted earth

This paper investigates the effect of stabilisation by alkaline activation and silicon based admixture on the mechanical properties, moisture buffering capacity and durability of an earthen material for building construction. The stiffness and strength of both unstabilised and stabilised cylindrical samples were measured, under different humidity conditions, by means of unconfined compression tests. The effect of stabilisation on moisture buffering capacity was instead explored by subjecting samples to cyclic variations of relative humidity at constant temperature, according to the experimental procedures prescribed by the norm ISO 24353 [21]. Finally, durability against water erosion was assessed by performing immersion, suction and liquid contact tests on both unstabilised and stabilised samples according to the norm DIN 18945 [16]. Results from this extensive experimental campaign highlighted that the chosen stabilisation methods improved the durability of the material while maintaining a relatively good mechanical performance and a good to excellent moisture buffering capacity

Valorisation de laitiers d'aciérie dans des blocs de béton d'enrochement

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ORIGINAL ARTICLE Recyclability, durability and water vapour adsorption of unstabilised and stabilised compressed earth bricks

International audienc