| Environnement, ingénierie & développement |  |
N°57 - Janvier-Février-Mars 2010
1. WASCON (Lyon, juin 2009) : où en est la valorisation des déchets en génie civil ?
2. Synthesis of binders using waste material
Industries produce large quantities of wastes that contain high fractions of silica and lime: sewage sludge, paper sludge, lime sludge, foundry sands, etc. Most of these wastes are currently disposed of in landfills, spread for agricultural purposes or incinerated. Two principal reasons lead to the proposition of environment-friendly alternatives to these present uses: the European directive 1999/CE of 26 April 1999 to limit the harmful effects of landfill disposal of waste, and the progressive decrease of spreading due to regulations.The project presented here aims to recycle wastes containing large quantities of mineralresources in order to synthesise hydraulic binders at temperatures not exceeding 1000°C. The ultimate goal is to manufacture hydraulic binders from 100% recycled waste, to be used mainly in road-building (backfill, sub-grade, etc.). The energy required for curing is obtained from substitute fuels produced from recycled waste.The project is divided into 4 phases:• Construction of a database of waste resources;• Selection in the laboratory of combinations of wastes for the synthesis of binders;• Industrial scale tests carried out in a rotary furnace;• Validation of the results in an industrial application (road test).This paper reports the results obtained so far.
3. The GeDSeT project: constitution of a decision support tool (DST) for the management and material recovery of waterways sediments in Belgium and Northern France
The European InterReg IV GeDSeT project (2008-2011) is a contribution to a sustainable management of waterways sediments, in order to develop good practice in a perspective of water resource protection and of the development of regional fluvial transport. Waterways sediments are a major environmental issue in the Walloon region of Belgium - Northern France trans-boundary region for several reasons, all of them resulting from the dense habitat, industrial pattern and waterways network, and of a long industrial history. Sediments affect water resources quality, through pollution, and availability, through flooding. Sediment dredging allows the development of environmentally-friendly regional fluvial transport, but also generates important waste deposits. Therefore material recovery for reuse in buildings or infrastructure is a key issue, as it allows a reduction of waste and limits the need for natural resources for the same use. In order to address waterways sediments management in a global way, the GeDSeT project intends to capitalise know-how regarding the criteria to take into account for a sustainable management, and to include them in a decision support methodology applicable to the transboundary context. Such decision support aims at developing good practice in a perspective of water resource management and development of regional fluvial transport. Relevant criteria include: - criteria evaluating the physical and chemical characteristics of the sediments to be dredged, […]
4. Influence of the cooling conditions on the nature and the size of the mineral phases in a Basic Oxygen Furnace (BOF) slag
This paper presents the influence of different cooling conditions on the nature and size of the major mineral phases present in a BOF slag. XRD, SEM and image analysis are used. The objective of this work is to optimise the industrial process in order to better recycle BOF slag.
5. Gas adsorption capacity of Municipal Solid Waste Incineration Bottom Ashes based materials
La présente étude porte sur la détermination des capacités d’adsorption des mâchefers d’incinération d’ordures ménagères (MIOM). Deux échantillons contenant des mâchefers ont été caractérisés vis-à-vis de leur propriétés physico-chimiques et structurales : analyse élémentaire, pH de surface, volume poreux et surface spécifique, observation microscopique couplée spectrométrie X. Les propriétés d’adsorption de ces matériaux vis-à-vis de l’H2S ont été déduites de mesures d’isotherme et cinétique en réacteur batch et leur performance en réacteur continu a été évaluée à partir de courbes de percée réalisées en lit fixe.Les résultats des caractérisations physico-chimique et structurale indiquent que les deux matériaux testés présentent des structures poreuses ainsi que des compositions et chimie de surface très proches et favorables à l’adsorption de gaz acide tel que l’H2S.Les isothermes et cinétiques d’adsorption de l’H2S ont été réalisées pour différentes conditions d’humidité et de température du gaz et pour différentes teneurs en eau des matériaux. Les résultats obtenus montrent l’influence globale de l’eau (humidité de l’air mais surtout teneur en eau de l’échantillon) sur les performances d’adsorption. Ainsi, pour les teneurs en eau élevées, les matériaux présentent des capacités d’adsorption du H2S équivalentes à celles de charbon actif mais pour des temps de contact […]
6. The study of the physico mechanical behaviour of a concrete with limestone sand renforced by synthetic fibers
Laghouat region (situated in the south Algeria) is among the parts of Algeria which have a large natural limestone deposit, which extends over the totality of the southern side of the Saharan Atlas. The exploitation of this material in the industry of coarse aggregates generates significant amounts of fine residues, currently badly or less exploited and meanwhile causes harm to the environment. In order to valorise this waste material and met the environmental requirements, the idea is to exploit these residues as limestone fine aggregate for concrete. Beside for enhancing the mechanical properties of concrete and exploit polypropylene fibres wastes resulting from the industry of brushes and sweep domestic, we decide to incorporate them in the limestone mortar.The study of the physical and mechanical properties of the limestone mortars reinforced by polypropylene fibres are presented in this article, with fibre content percentage varies between 0.5 and 4 wt%. In view of results obtained, we advance that the workability of limestone mortars is inversely influenced by the percentage content and the ratio l/d of polypropylene fibre, while their mechanical properties are generally enhanced.
7. Potential mobilization of inorganic contaminants in a french harbor sediment
As part of a French national research program called “SEDiGEST” concerning the management and the environmental risk assessment of contaminated marine harborsediments, the research presented in this paper focuses on the determination of theleachability of inorganic contaminants.In this objective, a methodology was developed and applied to investigate the mobility of inorganic contaminants as a function of physicochemical conditions. This methodology is based on the use of leaching tests in conjunction with mineralogical and textural analysis. Muddy sediment with important Organic Matter (OM) content (ca. 12 wt %) has been selected and collected from a French harbor. This sediment contained also ca. 109000 mg.kg-1 calcium (Ca), ca. 32 170 mg.kg-1 iron (Fe), ca.19 660 mg.kg-1 sulfur (S), ca. 2 120 mg.kg-1 zinc (Zn), ca. 1 730 mg.kg-1 copper (Cu), ca. 860 mg.kg-1 lead (Pb) and ca. 150 mg.kg-1 arsenic (As). In addition, this sediment had a natural pH and ORP (Oxidation Reduction Potential) of ca. 8.2 and ca. + 350 mV vs. Normal Hydrogen Electrode (NHE).Main results shown in this study indicate that the release of target contaminants (As, Cu, Pb and Zn) during a contact with deionized water is very limited (ca. <-0.1 wt %) by the very low solubility of solids, like sulfides or carbonated phases, and by the stability of their bearing solid phases (i.e., OM and/or sulfides) at natural slightly basic conditions. However, the natural pH of this matrix can vary with the loose of […]
8. Use of waste glass in cement-based materials
Demand for recycled glass has considerably decreased in recent years, particularly for mixed-glass. Glass is cheaper to store than to recycle, as conditioners require expenses for the recycling process. There are several alternatives for the reuse of composite-glass. According to previous studies, all these applications, which require pre-conditioning and crushing, are more or less limited and unable to absorb all the quantities of waste glass available. In order to provide a sustainable solution to glass storage, a potential and incentive way would be to reuse this type of glass in concretes.Depending on the size of the glass particles used in concrete, two antagonistic behaviours can be observed: alkali-silica reaction, which involves negative effects, and pozzolanic reaction, improving the properties of concrete. The work undertaken here dealt with the use of fine particles of glass and glass aggregates in mortars, either separately or combined. Two parameters based on standardised tests were studied: pozzolanic assessment by mechanical tests on mortar samples and alkali-reactive aggregate characteristics and fines inhibitor evaluations by monitoring of dimensional changes. It is shown that there is no need to use glass in the form of fines since no swelling due to alkali-silica reaction is recorded when the diameter of the glass grains is less than 1mm. Besides, fine glass powders having specific surface areas ranging from 180 to 540m² / kg reduce the expansions of […]
9. Identification of leaching-controlling process by differential analysis of acid neutralization for geochemical modeling – application to metal hydroxide sludge stabilization with coal fly ash –
L’identification des principales phases minérales contenues dans ces matériaux est nécessaire car ce sont ces phases minérales qui, en contact avec la phase aqueuse, vont réagir avec la phase aqueuse et libérer en solution les éléments polluants. Cette identification est très complexe du fait de l’influence du contexte géochimique sur la stabilité des hydrates cimentaires. La minéralogie du matériau peut être déterminée par des techniques d’observation microscopique (diffractométrie, analyse thermogravimétrique, microscopie électronique).Cette approche est cependant limitée et une modélisation géochimique basée sur les résultats de tests de lixiviation est nécessaire. En particulier, l’analyse différentielle des résultats du test de neutralisation acide permet de mettre en évidence les dissolutions de ces phases au cours de l’acidification de la matrice solide. Sur la base de ces résultats expérimentaux, un modèle géochimique peut être proposé. Après validation, les simulations permettent alors de considérer des conditions diverses d’exposition du matériau et de faire apparaître les points clé qui régissent le comportement du matériau.Les travaux présentés ici ont porté sur de boues d’hydroxydes synthétiques stabilisées/solidifiées par des liants hydrauliques. Les modélisations géochimiques ont été développées avec PHREEQC, logiciel bien adapté à l’étude des matériaux cimentaires.La mise en ouvre […]
10. Ecotoxic evaluation of mortar leachate using the amphibian larvae (Xenopus laevis)
Nowadays, many projects aim to reuse by-products (e.g. sewage sludge ash, sedimentsof dredging, MSWI…) in cement-based materials. However, some questions remainconcerning the environmental impacts of these wastes in this kind of application. Thecement-based materials in buildings or roads are subjected to leaching/draining byrainwater or subterranean water. Consequently, draining waters may constitute animportant reservoir for contaminants, such as water extractible elements, in the aquaticenvironment. So these elements, which are potentially pollutant, could be in contactwith living organisms of the ecosystems.The regulations in the field of waste materials are mainly based on the chemicalcomposition of the waste, or on the quantity of leached elements and use standard tests.However the quantity of elements that are potentially leachable does not necessarilyreflect the ecotoxic behaviour of the waste in the environment. The impact of a leachatedepends on many factors such as: the intrinsic toxicity of the elements, speciation ofmetals, the nature of the medium, and physical and chemical interactions leading to themodification of the bioavailability of the pollutants.In order to assess the ecotoxic potential of by-products used in cement-based materials,measurements were made to evaluate the effects of acute toxicity and the possibleeffects of toxicity on the genome (genotoxicity) of larvae of amphibians exposed tovarious concentrations of mortar leachates. This work is […]
11. Phosphorus speciation in dicalcium silicate polymorphs of basic oxygen furnace (BOF) slag - Preliminary results
This paper gives preliminary results of P speciation in basic oxygen furnace slag, rich in dicalcium silicates and with a phosphorus content that could jeopardize internal recycling within the steel mill.
12. Environmental assessment of a BOF steel slag used in road construction : The ECLAIR research program
Steel production generates great amounts of by-products as steel slag. Unlike blast furnace slag, the use of Basic Oxygen Furnace slag (BOF slag) has been restrained due to insufficient volume stability and to the lack of environmental regulations. This study aimed at investigating the potential release and impact of pollutants, especially Cr and V that are present in rather high concentrations in slag, from a BOF slag used in a civil engineering structure (an industrial platform), using a multi-scale approach. The oneyear follow up of the experimental platform showed that concentrations of Cr and V were generally low in seepage waters, and in leachates from leaching test. Microanalyses carried out on slag allowed us to confirm the location of these metals in rather stable ferrous mineral phases, but V was also bound to more reactive silicates. No real toxicity effect of seepage waters has been revealed from eco-toxicological tests carried out with earthworms.
13. Groundwater impact simulations for establishing criteria for the recycling of alternative materials in road construction
L’objectif de cet article est de présenter les résultats d’une modélisation des impacts potentiels sur la qualité des eaux souterraines liés à l’utilisation de matériaux alternatifs ou hors spécifications en sous couches routières ou en parking. Ces impacts potentiels ont été calculés dans le cadre des travaux du groupe de travail relatif à l'acceptabilité de matériaux alternatifs ou hors spécifications en techniques routières, mis en place par le Ministère de l’Ecologie de l’Energie du Développement Durable et de l’Aménagement du Territoire (MEEDDAT). Cet article présente les résultats de plusieurs scénarios d’utilisation : assise de chaussée de voirie ; assise de chaussée de parking ; remblai technique.Les modélisations ont été effectuées avec les codes de calcul du domaine public ModFLOW 2000 de l’USGS (pour la simulation des écoulements) et MT3DMS de l’US EPA (pour la simulation et le transport des polluants) en considérant 2 configurations hydrologiques, ainsi qu’une recharge de 300 mm/an et une recharge de 100 mm/an. Les modélisations de transport ont été réalisées en supposant plusieurs hypothèses sécuritaires : (1) infiltration des éluats issus de la lixiviation des matériaux considérés par les eaux de pluie directement dans les eaux souterraines à une « concentration source », notée Co, supposée constante et de durée illimitée ; (2) absence d’atténuation dans la zone non saturée) ; (3) […]
14. Ecotoxicological risks of road runoff water sediments on aquatic ecosystems
La gestion des résidus de l'assainissement routier (sédiments récupérés au fond des ouvrages de collecte des eaux de chaussées, balayures de chaussées, résidus de fossés) est un enjeu important sur les plans environnemental et socioéconomique. En plus du renforcement de la législation en matière de gestion des déchets, la valorisation de ces matériaux hétérogènes, produits en grandes quantités sur l'ensemble du territoire national, est limitée du fait de leurs caractéristiques physico-chimiques et de leur charge polluante (métaux lourds, hydrocarbures...).Le LCPC de Nantes a développé un procédé de traitement des résidus de l'assainissement routier dans le but d'aider à leur valorisation en travaux publics (Pétavy et al., 2007). Le procédé consiste en un criblage granulométrique des sédiments en fractions valorisables et en fractions non valorisables du fait de leur contamination et de la taille des particules (fines < 60 μm).Dans l'étude présentée dans cet article, des résidus bruts et traités ont été caractérisés sur le plan physico-chimique et soumis à des tests de lixiviation pour simuler le contact avec les eaux météoriques des matériaux mis en œuvre et l'extraction des polluants par l'eau. Des essais écotoxicologiques monoet plurispécifiques (microcosmes composés d'algues microscopiques, de lentilles d'eau, de daphnies, d'amphipodes et de chironomes) ont été […]