Rachid Zentar

International audience La prévision de la compacité (ou de la porosité) d'un mélange de grains secs est une vieille question, commune à bien des domaines techniques et scientifiques. Dans le domaine de la formulation des matériaux granulaires, on se restreint généralement à la question de la détermination des granularités conduisant aux compacités les plus fortes. Devant les difficultés théoriques qu'elle soulève, l'approche générale consistait à rechercher, par l'expérience à l'aide de courbes maîtresses, des distributions granulaires compactes et à tenter de s'en rapprocher en combinant les matériaux dont on dispose [SED 94].  En reprenant le problème dans son contexte général, et devant l'empirisme des approches conventionnelles, plusieurs modèles ont été développés antérieurement qui permettent de prédire avec une certaine précision la compacité d'un mélange granulaire. Le Modèle d'empilement compressible MEC proposé par DE LARRARD [DEL 00], q...

L'objectif de cet article est d'étudier le comportement rhéologique de la kaolinite. Une série d'essais rhéologiques de laboratoire a été réalisée à l'aide d'un rhéomètre de type MCR 102 à différentes vitesses de cisaillement. La pertinence de la résistance au cisaillement et de la viscosité apparente avec les rapports W/S est analysée en fonction des résultats expérimentaux. Pour prédire les données de contraintes de cisaillements et de vitesses de cisaillements différents modèles rhéologiques ont été utilisés. Les résultats indiquent que, le meilleur modèle rhéologique pour prédire les données est le modèle de Bingham modifié. Le seuil d'écoulement et la viscosité plastique de la kaolinite sont influencés par les rapports W/S. Les résultats de cette recherche peuvent contribuer à améliorer l'impression 3D de ce type de Matériel.

The work presented in this paper is undertaken in the framework of a methodology suggested to improve management of the marine and river sediments dredged in the north of France. The first stage of this methodology consists in determining the main characteristics of the sediments studied in relation to the field of valorisation considered. Thus, in this paper the physical, mineralogical and chemical properties of the two types of studied sediments are presented. Their environmental impacts are explored through leaching tests. From the obtained results, their beneficial use, in the field of road work, is discussed. Received 28 January 2008, accepted 27 November 2008, available online 9 February 2009. Translated version not certified, published under the responsibility of the article authors. 4.14 : Revue Paralia – n° 2 (2009)

Abstract Stabilization/solidification (S/S) of dredged sediments is an environmentally friendly, low-cost and time-efficient way to manage this waste (according to the European waste classification) in the context of valorization as novel resources. In this study, the main objective was to evaluate the efficiency of using a novel and green binder Calcium Sulfo-Aluminate (CSA) cement to solidified Dunkirk sediments. For comparison, the Ordinary Portland Cement (OPC) binder was used as a reference. For this purpose, several tests were performed on samples containing various types and amounts of binders. The experimental program included: modified Proctor compaction tests, immediate Californian Bearing Ratio (I-CBR) index tests, unconfined compressive strength tests, splitting tensile strength tests, measurements of elastic and secant modulus, and mineral and micropore structure analysis. It is realistic to conclude that the compaction performance of the CSA-/OPC-solidified sediments is significantly improves. The mechanical performance of compressive, tensile strength and elastic modulus increases with binder content and curing time. The simple model obtained to relate the compressive and tensile strength with elastic modulus allows predicting easily, for a given suitable set of characteristics, the type or the amount of binder needed. This model allows optimizing the amount of binder to reach a given properties of solidified sediments and hence improves the cost of developed material. The results also demonstrate the ability of solidified sediment to be valorized in road construction.

The management of marine sediments after dredging has become increasingly complex. In the context of sustainable development, traditional solutions such as immersion will be increasingly regulated. More than ever, with the shortage of aggregates from quarries, dredged material could constitute a new source of materials. In this study of the potential of using dredged marine sediments in road construction, the first objective is to determine the physical and mechanical characteristics of fine sediments dredged from a harbour in the north of France. The impacts of these materials on the environment are also explored. In the second stage, the characteristics of the fine sediment are enhanced for use as a road material. At this stage, the treatment used is compatible with industrial constraints. To decrease the water content of the fine sediments, natural decantation is employed; in addition, dredged sand is added to enhance the granular distribution and to reinforce the granular skeleton. Finally, the characteristics of the mix are enhanced by incorporating binders (cement and/or lime). The mechanical characteristics measured on the mixes are compatible with their use as a base course material. Moreover, the obtained results demonstrate the effectiveness of lime in the mixes. In terms of environmental impacts, on the basis of leaching tests and according to available thresholds developed for the use of municipal solid waste incineration (MSWI) bottom ash in road construction, the designed dredged mixes satisfy the prescribed thresholds.