Thermal power station in most countries is saddled with the problem of fly ash disposal and unless suitable avenues are found for its proper use, this would pose a gigantic problem to the power sector. Disposal of huge quantities of fly ashes without proper care causes considerable impact on the environment particularly the one leading to soil and groundwater contamination. On the other hand, fly ashes have many desirable properties which can find applications in civil engineering, especially in geotechnical engineering. The pozzolanic reactivity is one of the important properties of fly ashes that enhance its application. Thought the fly ashes with self – pozzolanic property are well utilized, fly ashes with insufficient free lime, such as class F fly ashes are being grossly underutilized and they form a considerable portion of fly ashes that are disposed. Yet another factor restricting the use of fly ash is the concern about the leachability of lime under field conditions particularly under saturated or partially saturated conditions. Hence an attempt is made in this thesis, to reduce the lime leachability of class F fly ashes with different additives. Thus, selection of right amounts of additives to reduce the lime leacability is an important aspect studied in this thesis. Effect of such as strength, compressibility, and CBR value is also investigated. Another simple way to reduce the problem of disposal of fly ash is to utilize it for the construction of waste disposal sites particularly for lining solid waste disposal facilities in place of the natural clay materials which are very often procured by excavating and transporting from far off places. Also, the capacities of fly ashes to sorb heavy metal that are likely to be present in the leachates generated from the industrial wastes have been studied. Of the other factors limiting the generous use of fly ashes is the leachability of several trace elements present in them. Hence the leachability of trace metals from fly ashes under different practical situations, before and after incorporating the selected additives for improving the engineering properties of fly ashes, has been studied. The thesis is presented in 10 chapters. The relevant background for the studies and scope of the work is given Chapter 1. Sources of the fly ashes collected for the investigating along with their physical and chemical properties are presented in chapter 2. Two low line fly ashes are collected directly from the electronic precipitators of the thermal power plants located at Neyvelli town of the Tamil nadu and Maddanur town of Andhra Pradesh, India, named NFA and MFA respectively. MFA has greater finer particle content than NFA. The particles of MFA Have rougher surface compared to those of NFA. Both of fly ashes have predominantly quartz and mullite phase in them. The silica, total lime and carbon contents which have major influence on the pozzolanic reactivity of fly ashes vary considerably in the both the fly ashes. Lime leachability is taken as the amount of lime that is converted into soluble form (by dissociation into calcium and hydroxyl ions) under a standardized condition. It can be used to asses the long term sustainability of the strength achieved in fly ashes with lime. Lime leachability studies have been conducted on the fly ashes stabilized with different additives in specially designed moulds. Results presented in Chapter 3 showed that leachability of lime in fly ashes increases with the increase in lime content though it is not in proportion to the increase in lime content. This is because the solubility of lime is less and is independent of the total lime present. The marginal reduction in leachability is mainly due to cemented matrix of fly ash inhibiting the leaching of time. The higher the strength of the matrix the lower is the leachability. Further it is made clear that at any lime content presence of gypsum reduces the time leachability which has been attributed to the transformation of pozzolanic compounds into less soluble form than the compounds formed with lime alone. With the increase in curing period, the amount of lime that leaches from the lime-stabilized fly ashes as well as those treated with gypsum to a considerable extent. The nature of alteration does not seem to change with time as revealed by a good correlation between lime leachability ratios obtained after 7 days and 14 days of curing periods. Chapter 4 presents the results of unconfined compressive strength tests carried out on fly ashes with varying lime and gypsum contents, before soaking and also soaking in several heavy metal solutions, along with the durability to the cycle of wetting and drying. The results revealed that the strength of low lime fly ashes increases with lime content significantly up to the optimum lime content of about 2.5 – 5% and gradually thereafter. Addition of gypsum of 1 – 2.5% increases the strength of fly ashes further at any lime content. Increase in strength with gypsum, which is quite significant at lower lime contents initially, is observed for a considerable period (up to 180 days) at higher lime contents. The increase in strength is as high as 40-fold in some instances. This increase in strength which is also more durable has been attributed to the formation of calcium – sodium – aluminium - silicate hydrate along with calcium silicate hydrate. Further, it is observed that fly ash which responds better to lime stabilization shows accelerated gain in strength due to the addition of gypsum at early curing periods than the fly ash that responds solely to lime. Decrease in lime leachability ratio is a good indication of the increased strength along with the increased durability. California Bearing Radio (CBR) values are of great significance in the utilization of fly ashes in bulk quantities for the construction of road and railway embankments and pavements. Studies conducted to determine the CBR values of fly ashes with different lime and gypsum contents after curing for different time periods are described in chapter 5. The CBR values are observed to increase with lime alone significantly up to 2.5% and only marginally beyond. But the increase in CRB values is considerable with gypsum at any lime content. The increase in CBR value is particularly more with 2.5% gypsum for fly ashes with 2.5% lime. The CBR values of stabilized fly ashes are generally higher for 5 mm depth of penetration than those for 2.5 mm one due to the high stiffness of the matrix formed even at low strain levels. The loss in CBR values with soaking is relatively more at lower curing the periods due to the improper cementation of particles. Even after this significant loss in CBR values, fly ashes with 2.5% lime and 2.5% gypsum register the maximum values after curing under soaked condition. Unlike in the case of unconfined compressive strength, lime leachability values could not be well correlated with the CBR values of fly ashes with different lime and gypsum contents since many more factors influence the CBR values than those of unconfined compressive strength alone. Chapter 6.brings out the effects of addition of lime alone and lime along with gypsum on the compressibility behaviour of the fly ashes. Since the fly ashes when treated with additives develop strength and exhibit lower compression with the passage of time, consolidation testing with conventional duration of load increment may not be appropriate. Hence an attempt has been made to assess the minimum duration of load increment necessary to study the compressibility characteristics of such materials. Thus the compressibility behaviour of fly ashes with additives has been studied using conventional consolidation test with different durations of load increments varying from 30 minutes to 48 hours. The results indicated that 30 minutes of duration of load increment can be used to assess the compressibility behaviour of such materials. The effect of lime which reduces the compression is seen to be maximum from the results obtained with the load duration increment of 30 minutes but gradually reduce with higher duration of load increment. It has also been observed that the rate of decrease in the compressibility is maximum up to 2.5% lime and thereafter gradual. The compressibility of lime –treated fly ashes further reduces when gypsum is incorporated, the optimum gypsum percentage being 2.5. This reduction in the compressibility of fly ashes enhanced by incorporating lime and gypsum makes them versatile in the construction of embankments and for structural fills, particularly reducing the time required in between laying of each lift. It has been brought out that decrease in the lime leachability decreases the compressibility of fly ashes. Fly ash has potential application in the construction of base liners of waste containment facilities. While most of the fly ashes improve in the strength with curing, the ranges of hydraulic conductivities they attain may often not meet the basic requirement of a liner material. Attempts to reduce the hydraulic conductivity by adding lime as gypsum along with lime to both the fly ashes are presented in chapter 7. Hydraulic conductivities of the compacted specimens have been determined in the laboratory using the falling head methods. It has been observed that the addition of gypsum reduces the hydraulic conductivity of the lime treated fly ashes. The reduction in the hydraulic conductivity of the fly ashes containing gypsum is significantly more of sample with high amounts of lime contents (as high as 1000 times) than those with lower amounts of lime. However, there is relatively more increases in the strengths of the samples with the inclusion of gypsum to the fly ashes even at lower lime contents. This is due to the fact that excess lime added to fly ash is not effectively converted in to pozzolanic compounds. Even the presence of gypsum is observed not to activate these reactions with excess lime. On the other hand the higher amount of lime in the presence of gypsum is observed to produce more cementitious compounds which block the pores in the fly ash. Amount of lime leached in the found to be directly related to the hydraulic conductivity inspite of many –fold variations in the hydraulic conductivity achieved by curing fly ash with lime and gypsum. The consequent reduction on the hydraulic conductivity of fly ash would be beneficial in reducing the leachability of trace elements in the fly ash when used as base liner. Fly ash contains trace metals and other substances in the sufficient quantities which may leach out over a period of time. The study has been extended to examine the leachability of a few selected trace metals viz., Cd, Cu, Cr, Mn, Pb and Zn from fly ash before and after incorporating additives has been reported in chapter 9. The standard laboratory leaching test for the combustion residues developed by Van der Sloot et al. has been employed to study the leachabilities of trace elements as a function of liquid to solid (L/S) ratio and pH. The leachability test were conducted on the powdered fly ash samples obtained from unconfined compressive strength tests, conducted after a curing period of 28 and 180 days. It observed that, there is a marked reduction in the relative leachabilities of trace elements present, at the end of 28 days which reduced only marginally at the end of 180 days. Chapter 9 reports the retention capacities of fly ashes for copper, lead and zinc metals ions. Various parameters like contact time, initial concentration and pH have been varied and their effect on retention mechanism studied. The retention order of metals ions, Cu+ 2 > Pb+2>Zn+2, is observed to be the same for both the fly ashes at all pH values. The dominant mechanisms responsible for the retention are precipitation at higher pH’s as hydroxides and adsorption at lower pH’s Due to presence of silica and alumina oxide surface in fly ash. First order kinetic plots have revealed that the rate constant value increases with increase in initial concentration and pH. Langmuir adsorption isotherms have been plotted to study the maximum adsorption isotherms have been plotted to study the maximum adsorption capacities for metal ions under different conditions. The older indicates that the adsorption is predominantly by silica surface than that by alumina or iron oxide surfaces. This thesis demonstrates that incorporation of gypsum along with lime in the optimal proportions not only reduces the lime leachability but also greatly enhances the strength and CBR values, reduces the compressibility and minimizes the leaching of trace elements present in them enhancing the potential of fly ashes for many applications. Detailed conclusions are presented in chapter 10. The study greatly helps in promoting the use of fly ashes for many geotechnical and geo-environmental applications.

D’après les limites d’acceptation pour la mise en décharge des déchets, les REFIOM (Résidus d’Epuration des Fumées d’Incinération d’Ordures Ménagères) sont considérés comme déchets dangereux, car ils libèrent des quantités importantes de chlorures et de métaux lourds lorsqu’ils entrent en contact avec de l’eau. Ces solides doivent par conséquent être traités avant leur mise en décharge. A côté des traitements visant l’acceptabilité des REFIOM en décharge, quelques recherches entrevoient la possibilité de valoriser ces résidus, notamment dans des matériaux cimentaires. Les recherches présentées ici s’inscrivent dans cette tendance nouvelle et visent l’élaboration d’un procédé combinant traitement et valorisation des REFIOM. Les REFIOM représentent en fait différents types de résidus provenant des installations que rencontrent les fumées issues de l’incinération des déchets. La composition des résidus diffère selon leur origine. Il est dès lors apparu essentiel de considérer chaque type de résidu séparément et de poursuivre l’élaboration d’un traitement sur un seul type de REFIOM. Nous avons choisi de concentrer les recherches sur les Cendres Volantes de Chaudière (CVC), ces résidus se retrouvant dans tout incinérateur. Le traitement des CVC est basé sur l’extraction de fractions valorisables et la séparation de fractions contaminées, permettant d’obtenir des résidus acceptables en décharge ou, idéalement eux-mêmes valorisables. Une séparation magnétique permet d’extraire environ 10% en poids des CVC mais ne semble pas exploitable dans le cadre du traitement des CVC car les particules magnétiques contiennent des impuretés (composés non magnétiques) et que le résidu final reste contaminé. Une étude de la répartition des éléments en fonction de la taille des particules (granulochimie) est effectuée sur les CVC. Il apparaît intéressant de séparer la fraction inférieure à 38 µm obtenue lors d’une séparation granulométrique, effectuée en voie humide en utilisant une solution dense. En effet, cette fraction semble être nettement plus contaminée en Pb (soluble) que le reste des CVC. Une telle séparation constitue dès lors la première étape du traitement des CVC. Elle est suivie par des étapes de lavage des fractions obtenues, visant à extraire les sels solubles (chlorures et métaux). Les lavages sont envisagés à contre-courant afin d’utiliser au mieux l’eau de lavage. Une recirculation interne des solutions est également prévue, de sorte que, théoriquement, le procédé ne génère pas d’effluents liquides. Une étape de précipitation de composés métalliques (PbS dans ce cas-ci) est prévue après le lavage des boues. Le procédé de traitement des CVC produirait ainsi des boues et des granulats décontaminés, des sels et des précipités métalliques. Seules certaines étapes du procédé ont été investiguées en laboratoire ; des essais supplémentaires sont encore nécessaires pour optimiser chaque étape, comprendre les phénomènes physico-chimiques qui se produisent et assurer des filières de valorisation. / Municipal Solid Waste Incineration (MSWI) fly ashes and Air Pollution Control (APC) residues are considered as hazardous waste according to the limits for the acceptance of waste at landfills, because high amounts of chlorides and heavy metals leach from the solids when those are in contact with water. These residues have thus to be treated before they can be accepted in landfill. Several treatments aim to limit the leaching of the residues. Beside these treatments, some research works go further the treatment and consider the valorisation of MSWI fly ashes and APC residues, e.a. in cementitious materials. The present work follows the new trend and aims to build up a process that combines treatment and valorisation of MSWI fly ashes and APC residues. MSWI fly ashes and APC residues come from the devices encountered by the flue gases from waste incineration. The residues composition differs according to their origin. It seems thus essential to consider each type of residues separately and to develop the treatment only on one sort of residue. Boiler Fly Ashes (BFA) were chosen because they exist in every modern MSWI plant. The BFA treatment is based on the extraction of valorisable fractions and on the separation of contaminated fractions, which makes the final residues less hazardous; these final residues would then be acceptable in landfill, or, even better, be valorisable. A magnetic sorting extracts ~10% (wt.) of BFA; however, such a separation would not be useful in a treatment process because the magnetic particles contain some impurities (non magnetic particles) and the final residue is still hazardous. The repartition of the elements according to the particles size has been studied on BFA. It seems interesting to separate the BFA at 38 µm by a wet sieving process using a dense solution. The lower fraction presents a higher contamination in Pb (soluble) than the larger. Consequently, the first step of the BFA treatment consists of a wet sieving. Washing steps follow the sieving and aim to extract soluble salts (chlorides, heavy metals). These washings work in a counter-current way to optimise the use of water. The solutions are recycled in the process, which implies the absence of liquid effluents. A precipitation step of some metallic compounds (PbS in this case) is foreseen after the washing of the lower fraction. The BFA treatment process would produce decontaminated sludge and coarse fractions, salts and metallic compounds. Some steps of the process have been investigated at lab-scale; further studies are necessary to optimise each step, to understand the observed reactions and to guarantee valorisation channels.

The aim of this work was to develop an alkali activated matrix based mainly on fly ash, to determine the ability to fix lead in these matrices, the impact of added lead on mechanical properties and to reveal the way of lead fixation in these matrices. The matrices consisted mainly of fly ash (four from fluidized bed combustion, one pulverized coal combustion) with an admixture of blast furnace slag and sodium silicate as an activator. Lechates were prepared on the basis of the ČSN EN - 12457-4 standard, lead concentrations in them were measured using an atomic emission spectrometer with inductively coupled plasma. The strengths of the samples were measured after 28 days. Images, element maps and element spectra were taken to determine the structure using a scanning electron microscope with an electron dispersion spectrometer, the samples were analyzed on an infrared spectrometer with a Furier transform, X-ray diffraction analysis and electron spectroscopy for chemical analysis were also used. The individual measurements showed that lead is accumulated in the form of hydroxide. The impact of lead doping on strength of the matrix was different for individual samples. Matrices from both types of fly ash released minimal amounts of lead into leachates, so it is possible to use them to fixate lead.

In this thesis, characterization of two class F fly ashes (FA) from &Ccedil / atalagzi and Sug&ouml / z&uuml / thermal power plants were carried out and their utilization potentials in three different fields were examined. Characterization of sintered samples and determination of their utilization potentials in ceramic industry is the first research area in this thesis. For this purpose, the class F fly ash samples were first pressed into cylindrical specimen without the addition of any organic binders or inorganic additives, and then sintered to form ceramic materials. Effects of sintering temperature and time on sintering characteristics were investigated. In the experiments, the cylindrical specimens were first preheated to 300oC for 1 h to remove moisture and any other gases. The specimens were then fired at the temperatures of 1000oC, 1050oC, 1100oC and 1150oC for the sintering times of 0.5, 1.0, 1.5 and 2.0 hours. Heating rate of 10oC/min was kept constant throughout the experiments. Quality of sintered samples was evaluated in terms of ceramic specifications such as density, water absorption, porosity, shrinkage and splitting tensile strength. In addition, mineralogical and microstructural changes during sintering were determined with X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. According to literature data, better microstructure, the highest density and strength with the lowest porosity, water absorption and shrinkage values are the indications of the optimum sintering conditions. Based on these specifications, Sug&ouml / z&uuml / fly ash gave better results compared to &Ccedil / atalagzi fly ash, and the optimum conditions were achieved at the sintering temperature of 1150oC for the sintering time of 1.5 hours for both samples. Pozzolanic reactivity of the fly ashes and their utilization potentials in civil engineering applications were also examined in detail during this study. For this purpose, &Ccedil / atalagzi (CFA) and Sug&ouml / z&uuml / (SFA) fly ashes were first subjected to a specific hydraulic classification process developed at CAER (University of Kentucky, Center for Applied Energy Research) to recover ultrafine fly ash particles. The overflow products with average particle sizes of 5.2 &mu / m for CFA and 4.4 &mu / m for SFA were separated from the respective as-received samples with average particle sizes of 39 &mu / m and 21 &mu / m. After the classification stage, the pozzolanic activities of these ultrafine fly ash fractions (UFA) and as-received samples were examined by preparing a number of mortar (mixture of Portland cement (PC), FA or UFA as partial cement replacement, sand and water) and paste (mixture of PC, FA or UFA as partial cement replacement and water) specimens. Control samples containing only PC were also prepared and tested through the experiments for the comparison of the results. In the mortar experiments, three different PC replacement ratios by FA and UFA (10%, 20% and 30%) were used to examine the effects of FA and UFA samples on the fresh and hardened mortar properties such as water requirement, compressive strength, drying shrinkage and water expansion. These mortar tests indicated that ultrafine fractions of &Ccedil / atalagzi (CUFA) and Sug&ouml / z&uuml / (SUFA) fly ashes provided more than 10% reduction in water demand compared to the control sample for 30% PC replacement. The mortar cubes containing CUFA and SUFA samples exhibited also higher strength development rates after 14 days compared to the ones with as-received samples and PC only. At the end of the curing age of 112 days, both CUFA and SUFA provided more than 40% increase in compressive strength compared to the control sample for the PC replacement ratios higher than 20%. As a comparison, SUFA gave better results than CUFA in both water demand and compressive strength tests. The mortar bars prepared with the both FA and UFA samples exhibited very low shrinkage and expansion values. These values decreased generally with increasing PC replacement ratio especially after 14 days. In the paste experiments, thermogravimetric analyses (TGA) of the paste specimens prepared by using only with 20% PC replacement were carried out to determine pozzolanic reactivity of the samples. The difference between the remaining Ca(OH)2 (portlandite) contents in the paste specimens containing the fly ashes and the reference PC paste was used as a measure of pozzolanic reactivity. After 112 days, 68.56% and 62.68% Ca(OH)2 content of PC only pastes were obtained with the pastes containing CUFA and SUFA samples, respectively, corresponding to 11% and 13% more Ca(OH)2 consumptions in reference to the respective as-received samples. X-ray diffraction (XRD) analyses were also performed for comparison of main portlandite peak intensities in the paste specimens containing FA or UFA with those in the PC only paste during cement hydration. According to these XRD analyses, portlandite content in PC/UFA pastes decreased significantly after 14 days compared to the PC only paste. All of these tests and analyses showed that a highly reactive lower cost pozzolan with very fine particle size and higher surface area compared to regular fly ash pozzolans can be produced from both &Ccedil / atalagzi and Sug&ouml / z&uuml / fly ashes using a relatively simple hydraulic classification technology. Cenosphere recovery potentials from &Ccedil / atalagzi and Sug&ouml / z&uuml / fly ashes were also studied in this thesis. Determination of cenosphere content was done under optical microscope by particle counting on the basis of point and area. Based on the point-counting data, CFA and SFA samples originally contain 11.30% and 4.50% cenospheres, respectively. Variations of cenosphere contents in the fly ash samples were examined by using float-sink, screening and air classification tests. The results pointed out that cenosphere contents decreased with decreasing size and increasing density for both samples. According to the float-sink tests, &Ccedil / atalagzi fly ash has much more floating products and more cenospheres than Sug&ouml / z&uuml / fly ash for the same density interval. Based on the air classification results, cenospheres were concentrated in the underflow products, and cenosphere contents increased with increasing air pressure and decreasing motor speed for both samples. The most efficient cenosphere separation technique among the examined methods was screening. Cenosphere contents of CFA and SFA increased to 21.65% and 11.83%, respectively by only using simple screening through 38 &mu / m.

L'optimisation de la composition des vitrifiats de REFIOM en les rendant alcali-résistants en vue de leur conférer une bonne durabilité chimique en milieu alcalin pour être ensuite utilisés dans les matrices cimentaires a été étudiée. La méthodologie suivie consiste à étudier le comportement à la lixiviation en mode statique de verres modèles alcali-résistants de type CEMFIL et de vitrifiats de REFIOM auxquels on a rajouté SiO2, Na2O et ZrO2 pour leur conférer un caractère alcali-résistant. Les tests de lixiviation menées à 90°C et à différents temps (de 6 heures à 28 jours) ainsi que les autres techniques d'analyse chimique (ICP-AES, MEB-EDS, SIMS, ERDA, RBS, PIXE) sur ces verres ont montré que ce sont les vitifiats de REFIOM dont la composition a été optimisée qui présentent la meilleure durabilité chimique quelque soit le pH / The main goal of this research work is to optimize the composition of vitrified REFIOM into alkali-resistant glasses in order to enhance their durability and in alkaline media. The expected industrial application deals with the use of these glasses associated with concrete in composite materials. The experimental approach is based on static leaching tests of model alkali-resistant glasses and vitrified REFIOM in witch we have added SiO2, Na2O et ZrO2 in order they become alkali-resistant vitrified REFIOM. The leachates have been analysed by ICP-AES and the solid surfaces characterized by scanning electron microscopy, electron microprobe analysis, secondary ion mass spectrometry depth profiling, and synchrotron radiation spectroscopies. All those analysis showed that alkali-resistant REFIOM are the best durability in every media

Fly ash and blast furnace slag are the two major industrial solid by-products generated in most countries including India. Although their utilization rate has increased in the recent years, still huge quantities of these material remain unused and are stored or disposed of consuming large land area involving huge costs apart from causing environmental problems. Environmentally safe disposal of Fly ash is much more troublesome because of its ever increasing quantity and its nature compared to blast furnace slag. Bulk utilization of these materials which is essentially possible in civil engineering in general and more particular in geotechnical engineering can provide a relief to environmental problems apart from having economic benefit. One of the important aspects of these waste materials is that they improve physical and mechanical properties with time and can be enhanced to a significant level by activating with chemical additives like lime and cement. Class-C Fly ashes which have sufficient lime are well utilized but class-F Fly ashes account for a considerable portion that is disposed of due to their low chemical reactivity. Blast furnace slag in granulated form is used as a replacement for sand to conserve the fast declining natural source. The granulated blast furnace slag (GBS) is further ground to enhance its pozzolanic nature. If GBS is activated by chemical means rather than grinding, it can provide a good economical option and enhance its utilization potential as well. GGBS is latent hydraulic cement and is mostly utilized in cement and concrete industries. Most uses of these materials are due to their pozzolanic reactivity. Though Fly ash and GGBS are pozzolanic materials, there is a considerable difference in their chemical composition. For optimal pozzolanic reactivity, sufficient lime and silica should be available in desired proportions. Generally, Fly ash has higher silica (SiO2) content whereas GGBS is rich in lime (CaO) content. Combining these two industrial wastes in the right proportion may be more beneficial compared to using them individually. The main objective of the thesis has been to evaluate the suitability of the class-F Fly ash/GGBS mixtures with as high Fly ash contents for Geotechnical and Geo-environmental applications. For this purpose, sufficient amount of class-F Fly ash and GGBS were collected and their mixtures were tested in the laboratory for analyzing their mechanical behavior. The experimental program included the evaluation of mechanical properties such as compaction, strength, compressibility of the Fly ash/GGBS mixtures at different proportions with GGBS content varying from 10 to 40 percent. An external agent such as chemical additives like lime or cement is required to accelerate the hydration and pozzolanic reactions in both these materials. Hence, addition of varying percentages of lime is also considered. However, these studies are not extended to chemically activate GBS and only GGBS is used in the present study. Unconfined compressive strength tests have been carried out on various Fly ash/ GGBS mixtures at different proportions at different curing periods. The test results demonstrated rise in strength with increase in GGBS content and with 30 and 40 percent of GGBS addition, the mixture showed higher strength than either of the components i.e. Fly ash or GGBS after sufficient curing periods. Addition of small amount of lime increased the strength tremendously which indicated the occurrence of stronger cementitious reactions in the Fly ash/GGBS mixtures than in samples containing only Fly ash. Improvement of the strength of the Fly ash/GGBS mixtures was explained through micro-structural and mineralogical studies. The microstructure and mineralogical studies of the original and the stabilized samples were investigated by scanning electron microscopy (SEM) and X-Ray diffraction techniques respectively. These studies together showed the formation of cementitious compounds such as C-S-H, responsible for imparting strength to the pozzolanic materials, is better in the mixture containing 30 and 40 percent of GGBS content than in individual components. Resilient and permanent deformation behavior on an optimized mix sample of Fly ash and GGBS cured for 7 day curing period has been studied. The Resilient Modulus (Mr) is a measure of subgrade material stiffness and is actually an estimate of its modulus of elasticity (E). The permanent deformation behavior is also important in predicting the performance of the pavements particularly in thin pavements encountered mainly in rural and low volume roads. The higher resilient modulus values indicated its suitability for use as subgrade or sub-base materials in pavement construction. Permanent axial strain was found to increase with the number of load cycles and accumulation of plastic strain in the sample reduced with the increase in confining pressure. Consolidation tests were carried on Fly ash/GGBS mixtures using conventional oedometer to assess their volume stability. However, such materials develop increased strength with time and conventional rate of 24 hour as duration of load increment which requires considerable time to complete the test is not suitable to assess their volume change behavior in initial stages. An attempt was thus made to reduce the duration of load increment so as to reflect the true compressibility characteristics of the material as close as possible. By comparing the compressibility behavior of Fly ash and GGBS between conventional 24 hour and 30 minutes duration of load increment, it was found that 30 minutes was sufficient to assess the compressibility characteristics due to the higher rate of consolidation. The results indicated the compressibility of the Fly ash/GGBS mixtures slightly decreases initially but increase with increase in GGBS content. Addition of lime did not have any significant effect on the compressibility characteristics since the pozzolanic reaction, which is a time dependent process and as such could not influence due to very low duration of loading. Results were also represented in terms of constrained modulus which is a most commonly used parameter for the determination of settlement under one dimensional compression tests. It was found that tangent constrained modulus showed higher values only at higher amounts of GGBS. It was also concluded that settlement analysis can also be done by taking into account the constrained modulus. The low values of compression and recompression indices suggested that settlements on the embankments and fills (and the structures built upon these) will be immediate and minimal when these mixtures are used. In addition to geotechnical applications of Fly ash/GGBS mixture, their use for the removal of heavy metals for contaminated soils was also explored. Batch equilibrium tests at different pH and time intervals were conducted with Fly ash and Fly ash/GGBS mixture at a proportion of 70:30 by weight as adsorbents to adsorb lead ions. It was found that though uptake of lead by Fly ash itself was high, it increased further in the presence of GGBS. Also, the removal of lead ions increased with increase in pH of the solution but decreases at very high pH. The retention of lead ions by sorbents at higher pH was due to its precipitation as hydroxide. Results of the adsorption kinetics showed that the reaction involving removal of lead by both the adsorbents follow second-order kinetics. One of the major problems which geotechnical engineers often face is construction of foundations on expansive soils. Though stabilization of expansive soils with lime or cement is well established, the use of by-product materials such as Fly ash and blast furnace slag to achieve economy and reduce the disposal problem needs to be explored. To stabilize the soil, binder comprising of Fly ash and GGBS in the ratio of 70:30 was used. Different percentages of binder with respect to the soil were incorporated to the expansive soil and changes in the physical and engineering properties of the soil were examined. Small addition of lime was also considered to enhance the pozzolanic reactions by increasing the pH. It was found that liquid limit, plasticity index, swell potential and swell pressure of the expansive soil decreased considerably while the strength increased with the addition of binder. The effect was more pronounced with the addition of lime. Swell potential and swell pressure reduced significantly in the presence of lime. Based on the results, it can be concluded that the expansive soils can be successfully stabilized with the Fly ash-GGBS based binder with small addition of lime. This is also more advantageous in terms of lime requirement which is typically high when Fly ash, class-F in particular, is used alone to stabilize expansive soils. Based on the studies carried out in the present work, it is established that combination of Fly ash and GGBS can be advantageous as compared to using them separately for various geotechnical applications such as for construction of embankments/fills, stabilization of expansive soils etc. with very small amount of lime. Further, these mixtures have better potential for geo-environmental applications such as decontamination of soil. However, it is still a challenge to activate GBS without grinding.

D’après les limites d’acceptation pour la mise en décharge des déchets, les REFIOM (Résidus d’Epuration des Fumées d’Incinération d’Ordures Ménagères) sont considérés comme déchets dangereux, car ils libèrent des quantités importantes de chlorures et de métaux lourds lorsqu’ils entrent en contact avec de l’eau. Ces solides doivent par conséquent être traités avant leur mise en décharge. A côté des traitements visant l’acceptabilité des REFIOM en décharge, quelques recherches entrevoient la possibilité de valoriser ces résidus, notamment dans des matériaux cimentaires. <p>Les recherches présentées ici s’inscrivent dans cette tendance nouvelle et visent l’élaboration d’un procédé combinant traitement et valorisation des REFIOM. <p>Les REFIOM représentent en fait différents types de résidus provenant des installations que rencontrent les fumées issues de l’incinération des déchets. La composition des résidus diffère selon leur origine. Il est dès lors apparu essentiel de considérer chaque type de résidu séparément et de poursuivre l’élaboration d’un traitement sur un seul type de REFIOM. Nous avons choisi de concentrer les recherches sur les Cendres Volantes de Chaudière (CVC), ces résidus se retrouvant dans tout incinérateur. <p>Le traitement des CVC est basé sur l’extraction de fractions valorisables et la séparation de fractions contaminées, permettant d’obtenir des résidus acceptables en décharge ou, idéalement eux-mêmes valorisables. <p>Une séparation magnétique permet d’extraire environ 10% en poids des CVC mais ne semble pas exploitable dans le cadre du traitement des CVC car les particules magnétiques contiennent des impuretés (composés non magnétiques) et que le résidu final reste contaminé. <p>Une étude de la répartition des éléments en fonction de la taille des particules (granulochimie) est effectuée sur les CVC. Il apparaît intéressant de séparer la fraction inférieure à 38 µm obtenue lors d’une séparation granulométrique, effectuée en voie humide en utilisant une solution dense. En effet, cette fraction semble être nettement plus contaminée en Pb (soluble) que le reste des CVC. Une telle séparation constitue dès lors la première étape du traitement des CVC. Elle est suivie par des étapes de lavage des fractions obtenues, visant à extraire les sels solubles (chlorures et métaux). Les lavages sont envisagés à contre-courant afin d’utiliser au mieux l’eau de lavage. Une recirculation interne des solutions est également prévue, de sorte que, théoriquement, le procédé ne génère pas d’effluents liquides. Une étape de précipitation de composés métalliques (PbS dans ce cas-ci) est prévue après le lavage des boues. <p>Le procédé de traitement des CVC produirait ainsi des boues et des granulats décontaminés, des sels et des précipités métalliques. Seules certaines étapes du procédé ont été investiguées en laboratoire ;des essais supplémentaires sont encore nécessaires pour optimiser chaque étape, comprendre les phénomènes physico-chimiques qui se produisent et assurer des filières de valorisation. <p>/<p>Municipal Solid Waste Incineration (MSWI) fly ashes and Air Pollution Control (APC) residues are considered as hazardous waste according to the limits for the acceptance of waste at landfills, because high amounts of chlorides and heavy metals leach from the solids when those are in contact with water. These residues have thus to be treated before they can be accepted in landfill. Several treatments aim to limit the leaching of the residues. Beside these treatments, some research works go further the treatment and consider the valorisation of MSWI fly ashes and APC residues, e.a. in cementitious materials. <p>The present work follows the new trend and aims to build up a process that combines treatment and valorisation of MSWI fly ashes and APC residues. <p>MSWI fly ashes and APC residues come from the devices encountered by the flue gases from waste incineration. The residues composition differs according to their origin. It seems thus essential to consider each type of residues separately and to develop the treatment only on one sort of residue. Boiler Fly Ashes (BFA) were chosen because they exist in every modern MSWI plant. <p>The BFA treatment is based on the extraction of valorisable fractions and on the separation of contaminated fractions, which makes the final residues less hazardous; these final residues would then be acceptable in landfill, or, even better, be valorisable. <p>A magnetic sorting extracts ~10% (wt.) of BFA; however, such a separation would not be useful in a treatment process because the magnetic particles contain some impurities (non magnetic particles) and the final residue is still hazardous. <p>The repartition of the elements according to the particles size has been studied on BFA. It seems interesting to separate the BFA at 38 µm by a wet sieving process using a dense solution. The lower fraction presents a higher contamination in Pb (soluble) than the larger. Consequently, the first step of the BFA treatment consists of a wet sieving. Washing steps follow the sieving and aim to extract soluble salts (chlorides, heavy metals). These washings work in a counter-current way to optimise the use of water. The solutions are recycled in the process, which implies the absence of liquid effluents. A precipitation step of some metallic compounds (PbS in this case) is foreseen after the washing of the lower fraction. <p>The BFA treatment process would produce decontaminated sludge and coarse fractions, salts and metallic compounds. Some steps of the process have been investigated at lab-scale; further studies are necessary to optimise each step, to understand the observed reactions and to guarantee valorisation channels. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

Les REFIOM (Résidus d'Epuration des Fumées d'Incinération des Ordures Ménagères) issus de l'incération des déchets ménagers contiennent des métaux lourds comme le plomb ou le cadmium et sont en France uniquement stockés en centre d'enfouissement technique de classe 1 pour dangereux, en étant stabilisés par une vitrification. Afin de trouver des solutions pour le stockage ou la valorisation à long terme des REFIOM sans danger pour l'environnement, nous avons ciblé les vitrocéramiques et les céramiques frittées à hautes températures et hautes pressions. Nous avons utilisé des méthodes de la minéralogie physique par l'intermédiaire de synthèses à hautes températures, de synthèses à hautes températures et à hautes pressions en autoclave à chauffage externe, d'observations en microscopie électronique à balayage, de microanalyses chimiques EDX (Energy Dispersive X-Ray spectrometry), d'analyses en microsondes, de caractérisation structurale par diffraction de rayons X et d'expériences de lixiviation dynamique. Nous avons mis au point des protocoles de synthèses et d'analyses. Par ce biais, nous constatons pour les vitrocéramiques que le plomb ou le cadmium sont incorporés dans des cristallites et dans des nouvelles phases cristallines, eux-mêmes englobés dans une matrice vitreuse. Cette voie dite "double barrière" (cristaux + verre) semble prometteuses pour l'immobilisation du plomb et du cadmium (au regard des analyses EDX et des expériences de lixiviation). Pour les céramiques frittées, comme pour les SYNROC (SYNthetic ROCk) synthétisées pour les déchets nucléaires, de nouvelles phases cristallines incorporant Pb et Cd sont observées et seraient a priori résistantes pour le stockage de ces éléments toxiques. Dans ces deux cas de nouveaux matériaux capables d'incorporer massivement du plomb et du cadmium ont été mis en évidence. Des tests de durabilité permettront d'envisager une valorisation éventuelle de tels matériaux / MSWI 5Municipal Solide Waste Incinerator) fly ashes from the incineration of domestic waste contain heavy metals such as lead or cadmium. In France, these fly ashes are only stored under vitrified forms in class-1 type landfills for hazardous waste. In order to find solutions for long-term storage or valorization of the MSWI fly ashes, we studied glass-ceramics and sintered ceramics at high pressures and/or hight temperature. We used methods of mineral physics to : synthetize at high temperature, synthetize at higt temperature and high pressure using autoclaves with external heating system, observe by electron microcopy, make EDX (Energy Dispersive X-Ray spectrometry) chemical microanalysis, make microprobe analysis, structurally characterize and perform leaching test. We established experimental protocols for the synthesis and analysis of produced materials. For glass-ceramics, we observe that lead and cadmium are incorporated inside expected crystallites and new crystal phases, themselves embedded by a glassy matrix. This so-called "double barrier" (crystals + glass) is a promising way towards a substainable of lead and cadmium (after EDX analysis and leaching experiements). For sintered ceramics, as for the SYNROC (SYNthetic ROCk) with nuclear waste, new crystal phases incorporating Pb and Cd are found and might display a high resistant for the storage of these toxic elements. In both cases, new materials incorporating large amounts of lead and cadmium were formed. Durability tests may give new ways for a valorization of such materials

Soil is one of the largest ecosystems being ignored by human activities. Our farming practices and urban constructions have contributed to its degradation, with far-reaching consequences for the water cycle’s equi- librium.Reconnect with nature and learn the methods to assist in its recovery are essential for the survival of all inhabitants on this planet.  My degree project consists of a large research into the water cycle of urban areas, studying the particular case of Stockholm, that leads to the problems of degraded soil. The aim is to understand the relation- ship between water cycle and soil ecosystems and explore potential solutions.  As a result, I have designed KURITA, a learning tool founded upon the ecofeminism values of care, that serves as a learning method for citi- zens to reconnect with soil values and actively participate in its restor- ative process.