Influence of Fine Dune Sand on the Modulus of Elasticity of Eco-Self-Compacting-Concrete

The aim of this research was to study the effect of fine dune sand on the mechanical performance of Eco-Self-Compacting Concrete (SCC). For that, the fine dune sand of the Western erg (Taghit -Algeria) was being like mineral addition to formulate the SCC, and a comparison was carried out on their effect on the properties of SCC. Our study also showed that the substitution of fine dune sand (DS) by cement in the composition of the SCC, contributes to a slight variation of workability in the fresh state parameters still remaining in the field of SCC required by the AFGC recommendations. The experimental results show that the compressive strengths and modulus of elasticity of SCC improved by substituting of 20% cement by DS

Contribution à la valorisation du sable de dune de l erg occidental (Algérie)

Le sud de l Algérie est connu pour ces immenses dunes de sable qui recouvrent une partie de son territoire (Sahara). Ce sable présente des caractéristiques qui permettent d entrevoir une valorisation dans le domaine de la construction sous forme de Béton à Ultra Hautes Performances (BUHP). Ce type de béton utilise en grande quantité de la fumée de silice, addition ultrafine qui lui confère ses performances très élevées, mais qui est aussi relativement rare et chère. Son remplacement par une autre addition à propriétés équivalentes, tel que le métakaolin, peut aussi être envisagé. L objectif de cette étude est donc à la fois de valoriser le sable de dune de l erg occidental du sud ouest de l Algérie mais aussi de diminuer les coûts de fabrication des Bétons à Ultra Hautes Performances en y incorporant du métakaolin à la place de la fumée de silice. Les performances à déterminer sont des performances mécaniques instantanées, en compression et en flexion, et différées, sous forme de retrait et de fluage, ainsi que des propriétés de durabilité. Dans un premier temps, nous avons caractérisé les sables de dune algériens. Puis, nous avons procédé à la recherche d une formulation de BUHP, adéquate en terme de mise en œuvre et permettant de remplacer la fumée de silice par le métakaolin. Enfin, nous avons étudié la valorisation proprement dite du sable de dune. Les bétons obtenus présentent des performances mécaniques très élevées, allant jusqu à une résistance en compression de 250 MPa, une résistance en traction par flexion de 45 MPa et une résistance à la traction directe d environ 20 MPa, avec le mode de traitement thermique approprié. Ils présentent aussi un très bon comportement différé, y compris sous charge, ainsi que d excellents indicateurs de durabilité. Cette étude montre que la valorisation du sable de dune étudié est tout à fait possible dans les BUHP, et en particulier les BUHP fibrés, et que le remplacement de la fumée de silice par le métakaolin n altère pas les propriétés de ces bétonsThe south of Algeria is known for these immense sand dunes which cover part of its territory (the Sahara). This sand present of the characteristics which make it possible to foresee a valorization in the field of construction in the form of concrete with Ultra High Performances (UHPC). This type of concrete uses in great quantity of the silica fume, ultrafine addition which confers its very high performances to him, but which is also relatively rare and expensive. Its replacement by another addition with equivalent properties, such as the metakaolin, can also be considered. The objective of this study is thus at the same time to develop the sand of dune of the Western erg of the western south of Algeria but also to reduce the manufacturing costs of the Concretes with Ultra High Performances while incorporating in it of the metakaolin in the place of the silica fume. The performances to be determined are mechanical performances instantaneous, in compression and inflection, and differed, in the form of shrinkage and of creep, as well as properties of durability. Initially, we characterized Algerian sands of dune. Then, we proceeded in the search of a formulation of UHPC, adequate in term of implementation and allowing replacing the silica fume by the metakaolin. Lastly, we studied the valorisation itself of the sand of dune. The concretes obtained present very high mechanical performances, going until a resistance in compression of 250 MPa, a resistance in traction by inflection of 45 MPa and a tensile strength direct from approximately 20 MPa, with the mode of suitable heat treatment. They present also a very good differed behaviour, including under load, as well as excellent indicators of durability. This study shows that the valorization of the sand of dune studied is completely possible in the UHPC, and in particular the fiber UHPC, and that the replacement of the silica fume by the metakaolin do not deteriorate the properties of these concretesTOULOUSE-INSA (315552106) / SudocSudocFranceF

Durability of the Ultra High Performances Concrete containing metakaolin

WOS:000375166900102International audienceThe aim of this study is to determine the durability performances of the Ultra High Performances Concretes containing the silica fume instead of metakaolin. In our previous article entitled "Metakaolin in the Formulation of the UHPC", we sought a formulation of UHPC, adequate in term of implementation and allowing replacing the silica fume by the metakaolin. The valorization of the metakaolin in the UHPC has been studied. The obtained concretes present very high mechanical performances, reaching a resistance in compression of 250 MPa, a resistance in traction by inflection of 45 MPa and a tensile direct strength of approximately 20 MPa, under a suitable heat treatment mode. It has been previously shown, with this same formulation, that it was possible to replace the silica fume by the metakaolin which does not affects the durability performances of these concretes. The results of the permeability of oxygen diffusion, migration of the chloride ions and carbonation confirm good durability properties of UHPC containing metakaolin. (C) 2016 Elsevier Ltd. All rights reserved

Metakaolin in the formulation of UHPC

International audienceSilica fumes have characteristics that make them exceptional in cement matrices and, in particular, in UHPC. Nevertheless, they have important disadvantages: lack of availability, cost and color. The search for substitute products thus appears important if the use of UHPC is to become more widespread in the concrete industry, e.g. in the fields of mechanical engineering (machine parts, tools, molds, etc.) and civil engineering (pipes for water or waste water conveyance for example).The substitute product used in this study was metakaolin obtained by fixed-bed calcination. It proved to be almost equivalent to silica fume in terms of mechanical properties and durability. Kaolinite, the clay from which metakaolin is produced, readily available in most countries, so the price of this ultra fine is acceptable. Moreover, its white color gives it an esthetic advantage