Jean-Emmanuel Aubert

Quantitative mineralogical composition of complex mineral wastes – Contribution of the Rietveld method

The objective of the work presented in this paper is the quantitative determination of the mineral composition of two complex mineral wastes: a sewage sludge ash (SSA) and a municipal solid waste incineration fly ash (MSWIFA). The mineral compositions were determined by two different methods: the first based on calculation using the qualitative mineralogical composition of the waste combined with physicochemical analyses; the second the Rietveld method, which uses only X-ray diffraction patterns. The results obtained are coherent, showing that it is possible to quantify the mineral compositions of complex mineral waste with such methods. The apparent simplicity of the Rietveld method (due principally to the availability of software packages implementing the method) facilitates its use. However, care should be taken since the crystal structure analysis based on powder diffraction data needs experience and a thorough understanding of crystallography. So the use of another, complementary, method such as the first one used in this study, may sometimes be needed to confirm the results.

Plant aggregates and fibers in earth construction materials: A review

Abstract Earth as a building material is increasingly being studied for its low environmental impact and its availability. Plant aggregates and fibers have been incorporated into the earth matrix in the aim of enhancing performance for thousands of years but scientific studies began quite recently. The present paper reviews the state of the art of research on the influence of these various natural and renewable resources in unfired earth materials such as compressed earth blocks, plasters, and extruded and stabilized blocks. This review, based on 50 major studies, includes characterization of the particles and treatments, and recapitulative tables of the material compositions, and the physical, mechanical, hygrothermal and durability performances of earth-based materials. A lack of references on hygroscopic and durability properties was observed. Future research orientations are thus suggested to promote and develop this type of sustainable material, which provides a solution for saving energy and natural resources.

Quantification of Hydraulic Phase Contained in a Basic Oxygen Furnace Slag

AbstractThe aim of the work presented here was to quantify the mineralogical phases contained in a basic oxygen furnace slag (BOFS), and especially the hydraulic phases, so as to evaluate the reactivity of this material. The chemical and mineralogical characteristics of BOFS were analyzed. This slag was essentially composed of calcium, iron, silicon, and magnesium oxides contained in five main minerals: calcium silicate oxides (β-Ca2SiO4 and Ca3SiO5), a solid solution of calcium aluminum ferrite oxides (Ca2Fe1.52Al0.48O5), a solid solution of magnesium iron oxides (MgO0.432FeO0.568), and free lime CaO. The Rietveld method was used to determine the amount of each mineral phase and led to the following mineralogical composition: β-Ca2SiO4=32%, Ca3SiO5=2%, Ca2Fe1.52Al0.48O5=26%, MgO0.432FeO0.568=22%, and CaO=18%. BOFS thus contained a significant amount of hydraulic phase (dicalcium silicate and free lime), which was confirmed by the study of its reactivity using a hydrated paste.

Influence of various parameters on heat-induced internal sulphate attack

The work presented in this article studies the effects of some parameters that can be considered, a priori, as important in the appearance of delayed ettringite formation (DEF). The parameters studied are the nature of the binder, the water/cement (W/C) ratio, the preliminary microcracking (wetting–drying cycles) and the curing conditions. The results presented show that the chemical composition of cement is one of the main parameters controlling the appearance of DEF. The other parameters studied, (W/C ratio, wetting–drying cycles and temperature of curing water) principally modify the kinetics of the expansion: it seems that, the more favourable the conditions are to ionic and hydrous transfers, the sooner the expansion starts. Finally, the renewal of the curing water strongly affects the start of DEF. In one case of the study, the renewal of the curing water only accelerated the start of the expansion. In the second, it led to late starting of DEF (four years) whereas the same mixture cured continuously in water that was not renewed still had not expanded after more than five years. L’étude présentée dans cet article a pour objectif d’observer les effets de certains paramètres que l’on peut qualifier a priori d’importants vis-à-vis de l’apparition de la DEF. Les paramètres étudiés sont la nature du liant, le rapport E/C des mélanges, le préendommagement des éprouvettes (cycles d’humidification-séchage) et, enfin, les conditions de conservation des échantillons. Les résultats présentés montrent que la composition chimique du ciment est l’un des principaux paramètres contrôlant l’apparition de la DEF. Les autres paramètres étudiés (rapport E/C, cycles d’humidification-séchage et la température de l’eau de conservation des échantillons), modifient principalement la cinétique de l’expansion: il semble que plus les conditions sont favorables pour améliorer les transferts ioniques et hydriques, plus l’apparition des expansions est accélérée. Enfin, le renouvellement de l’eau de conservation affecte fortement le début de l’apparition de la DEF. Dans un cas d’étude, il n’a fait qu’accélérer le début de l’expansion. Dans un second cas, le renouvellement de l’eau de conservation a permis le déclenchement de la DEF au bout de 4 ans, alors que le même mélange conservé en permanence dans l’eau qui n’a pas été renouvelé n’avait pas encore montré de gonflement après plus de 5 ans.

Carbonation of municipal solid waste incineration electrostatic precipitator fly ashes in solution

Carbonation was applied to a Pb- and Zn-contaminated fraction of municipal solid waste incineration electrofilter fly ashes in order to reduce heavy metal leaching. Carbonation tests were performed in solution, by Na2CO3 addition or CO2 bubbling, and were compared with washing (with water only). The injection of CO2 during the washing did not modify the mineralogy, but the addition of Na2CO3 induced the reaction with anhydrite, forming calcite. Microprobe analyses showed that Pb and Zn contamination was rather diffuse and that the various treatments had no effect on Pb and Zn speciation in the residues. The leaching tests indicated that carbonation using Na2CO3 was successful because it gave a residue that could be considered as non-hazardous material. With CO2 bubbling, Pb and Zn leaching was strongly decreased compared with material washed with water alone, but the amount of chromium extracted became higher than the non-hazardous waste limits for landfilling.

Effect of wetting-drying cycles on mortar samples affected by DEF

This article, which deals with the effect of wetting–drying (W-D) cycles on materials affected by delayed ettringite formation (DEF), has two main objectives. The first is to observe whether W-D cycles pre-damage samples, by using the replica technique. Scanning electron microscopy (SEM) observations of replicas show that W-D cycles lead to microcracks in the samples. The second objective of the study is to observe whether the cycles are necessary for development of DEF or if they only accelerate DEF. A study of the expansion of the samples shows that cycles accelerate the appearance of expansion but they are not a prerequisite for triggering DEF. Cet article, qui porte sur l’effet des cycles d’humidification-séchage des matériaux atteints de DEF, a deux objectifs principaux. Le premier objectif est d’observer par l’utilisation de la technique de la réplique, si les cycles d’humidification-séchage pré-endommageaient les échantillons. Les résultats obtenus par le suivi des répliques ont permis de conclure que les cycles pré-endommagent les éprouvettes. Le second objectif de cette étude, est d’observer si les cycles sont nécessaires au développement de la DEF ou s’ils ne font qu’accélérer la DEF. Le suivi des expansions a montré que les cycles permettent d’accélérer l’apparition des expansions, mais qu’ils ne sont pas un préalable nécessaire pour le déclenchement de la DEF.

Effect of Plant Aggregates On Mechanical Properties Of earth bricks

AbstractA building material is mainly characterized by its mechanical performance, which provides proof of its quality. However, the measurement of the compressive or flexural strength of an earth-...

Management of mineral wastes in cement-based materials

ABSTRACT This paper, which enters in a sustainable development approach, aims to present a method developed by Laboratoire Matériaux et Durabilité des Constructions (LMDC) in Toulouse, for the assessment of the recycling of waste as secondary raw materials in cementbased materials used in civil engineering applications. The approach includes two parts carried out simultaneously: (i) a technological part, the aim of which is the evaluation of the effect of wastes on the chemical, physical and mechanical properties of fresh and hardened concrete; (ii) an environmental part, mainly based on leaching tests, in order to evaluate the environmental impact of wastes used in concrete materials. The method is illustrated with various cases taken from past studies performed in LMDC.