Caractérisation en laboratoire de l'enfoncement d'une cage d'armatures dans le béton frais

International audience Les travaux présentés ici rentrent dans le cadre du projet de bétons de fondations profondes financé par la FNTP. Ils s'intéressent aux problèmes de mise en œuvre rencontrés sur les chantiers de pieux forés à la tarière creuse, parmi lesquels la difficulté d'introduction de la cage d'armatures après le bétonnage du pieu. Ils se proposent de valider un protocole d'essai de laboratoire permettant de caractériser l'enfoncement d'une cage d'armatures en fonction de la charge qui lui est appliquée et du temps de repos du béton. Pour ce faire, des essais expérimentaux ont été réalisés sur une formulation courante de béton de pieu pour étudier l'effet du temps de repos sur les propriétés rhéologiques du béton et la capacité des armatures à y pénétrer. Les résultats obtenus ont permis de déterminer, pour le dispositif proposé, les paramètres d'essai à prendre en compte. </div

Mechanical and thermo-physical characterization of mortars made with uncontaminated marine sediments

International audienc

Experimental study on the valorisation of poplar by products in cement-based materials

ACTIInternational audienc

DETERMINATION OF THE MECHANICAL PROPERTIES OF CEMENTITIOUS MIXTURES WITH SEDIMENTS: EXPERIMENTAL AND NUMERICAL APPROACHES

International audienceSediment management is increasingly oriented towards valorization processes in several fields. Many researches have been conducted on the characterization of sediments and the possibility to be used as raw materials in the field of civil engineering. The overall objective of this contribution is to setup a numerical modeling strategy with a validation on the basis of experimental results. The mechanical strengths (flexural and compressive) and the elastic modulus were investigated. Five mortars were formulated with different substitution of sand by sediments (from 0% to 40%). A numerical model was built using the finite element method (FEM) based on homogenization technique. This model allows the prediction of the global mechanical behavior of the mortars based on the knowledge of the mechanical behavior of each phase constituting these samples. The model was validated through an example of a microstructure of a BOF (Basic Oxygen Furnace) slag from literature work. The microstructure has been observed using Scanning Electron Microscope SEM in order to identify the major phases in presence. Besides, the elastic properties of these phases have been determined using an instrumented indentation technique coupled with SEM. The obtained results show a good agreement between numerical and experimental. The model is validated and can then be applied on the mortars. The mechanical properties of the formulated mortars decrease with the increase of sediment substitution similarly to the obtained results in literature

Feasibility study of using poplar wastes as sand in cement mortars

International audienc

Optimizing mortar extrusion using poplar wood sawdust for masonry building block

ACLThe wood industry generates some 12 million tons of waste in France, 60% of which basically stems from sawmills. The reuse of this waste in the most common construction materials (e.g., concrete) may offer a sustainable solution. In the literature, the optimization of composites formulations generally focuses on aggregates plant pretreatment regardless of classical optimization parameters and the implementation process that can afford to get a high strength composite. The work presented herein is intended to optimize the mix design of a mortar made from poplar wood by-products, without involving any pretreatment. The conventional mix design parameters (i.e., paste volume, W/C ratio) have been varied. An optimal implementation technique (i.e., extrusion) was used. The wood mortar mix designs have been optimized in order to obtain composites compliant with French standard NF EN 771-3/CN, with respect to criteria regarding both dimensional tolerance and mechanical strength for structural elements (i.e., above 8 MPa at 7 days).A mortar mix design, optimized by means of extrusion, has been used as a reference. Poplar wood particles have been introduced through substitution for the sand volume. Test results indicate that the blocks produced from two wood mortar mixes with 60 and 70% wood aggregate-for-sand substitution rates are in line with the normative requirements relative to dimensional tolerances and mechanical strength. This material compliance underscores the potential use of such blocks as load-bearing masonry elements, thus facilitating the building of structures with a limited environmental impact