Sylvie Rossignol

• PhD
• Professor (Full) at Center european ceramic

In this study, the local‐scale structure of geopolymers shaped by extrusion or 3D printing was investigated and correlated to the reactivity of the raw materials. The reactivity of the different metakaolin mixtures was evaluated using zeta potential measurements with different alkali silicate solutions, followed by shaping via 3D printing; addition...

Geopolymer matrix composites (GMCs) are actively being developed for high‐temperature applications. In this work, we investigated different composite preparation parameters, such as the elaboration conditions (time, temperature and pressure) and composite dimensions (number of folds and surface area). In addition, we studied the effect of alkali ca...

The objective of this study was to investigate the impact of the geographic and climatic conditions on laterites properties and on geopolymerization based-laterite. Four different laterite deposits in the four geographical zones of Cameroon were studied. This included the center, north, south and west corners of Cameroon, having chemical compositio...

This study aims to demonstrate the differences between two series of metakaolin-based geopolymers obtained from silicate solutions with different potassium concentrations (5 and 6 mol/L). First, the differences between the two solutions were identified by performing ²⁹Si MAS-NMR, Raman and infrared spectroscopies. The reactivity of the solution was...

A microstructural approach to the prediction of heat flux transport in porous geopolymers is used experimentally to under- stand the effects of the pore size distribution and pores connectivity to the transfer of the thermal flux across the porous network of geopolymers. Controlling the mix design and the concentration of porogen agent, capillary p...

An optimized sol–gel protocol was carried out to produce an yttrium aluminum garnet (YAG) xerogel from aluminum alkoxide and an yttrium salt on a semi-pilot scale. This xerogel was successfully used without prior pyrolysis as a solid load with the aid of additives in the preparation of pastes. Thermal treatment of the green bodies, obtained by robo...

Geopolymers can be optimized to have interesting physical characteristics, which are influenced by the raw materials and additives utilized in their formulations. For this reason, various formulations of two metakaolin-based binders with filler additions of different natures, i.e., sands and carbonates, were tested. The aluminosilicate source used...

With the goal of developing refractory pastes to replace metal alloys used in turbine blades for Deep Space exploration, the French Space Agency, CNES, in collaboration with the Institute of Research for Ceramics, IRCER, has developed a preliminary research where dense alumina ceramics were formulated, printed and tested. This preliminary research...

This study was undertaken in the context of Cigéo project to investigate the use of geopolymer for potential applications in high level waste cell. The aim was to evaluate the structural evolution of potassium metakaolin based geopolymer as a function of time and temperature for geological nuclear waste disposal applications. The evolution of mecha...

In order to develop fire resistant geopolymer materials, it is necessary to understand the parameters controlling their thermal behavior such as the content of alkali or rare earth cations. This study highlights the effect of carbonate nature and amount on the thermal behavior of geopolymers in order to propose a model of thermal behaviour and pred...

This chapter aims to highlight the effect of clay mixture mineral composition and alkali concentration of potassium alkaline solutions on the thermal behavior of geopolymer materials. For this, three mixtures composed of kaolin (pure, impure kaolin or mixture of both), calcium carbonate, sand and potassium feldspar and three potassium alkaline sili...

Acid‐based geopolymers are known for their high temperature resistance and good mechanical performances. Some compositions also exhibit water resistance, which make them suitable for outdoor applications. This work aims to understand accurately the steps occurring during the geopolymerization process and focuses on the type of networks forming at e...

The shrinkage of geopolymer materials is an important parameter to control for several applications. In this topic, this study aims to investigate the role of used precursors (metakaolin and alkaline solution) and different additives (sand, normalized sand, wollastonite, and glass fibers) on the shrinkage. For this, different samples were synthesiz...

Thermophysical and microstructural behavior of eleven tropical woods widely available and commonly used was investigated. Experimental measurements of thermal conductivity and thermal diffusivity of wood were performed using the heat flow meter and transient plane source technique. The results show values in the range of 0.2–0.37 mm2/s for thermal...

The present work carried out the influence of curing cycles on the performance of laterite-based geopolymer composites. To do so, the end products were obtained by altering laterite with 15, 20, and 25 wt% of rice husk ash (RHA). Alkaline solution in a constant solid/liquid ratio of 0.35 was added together with fine and coarse aggregates (represent...

This study aims to explore geopolymer binders and mortars based on local Moroccan clays and sands as coatings for the restoration of historical monuments in Morocco. For this, five substrates, one geopolymer binder, and two geopolymer mortars were investigated. The characterization of substrates reveals differences in terms of pH value, capillarity...

Kaolinite and its dehydroxylated forms are widely used in industry, including the growing field of geopolymers. Until now, a deep understanding of the dissolution mechanism of kaolinite particles in alkaline media is still lacking. This work aims to investigate the dissolution mechanisms through aluminum and silicon leaching of two references kaoli...

Three Moroccan clays, denoted A1, A3 and A5, were sampled from the Fez region with the aim of potential use as aluminosilicate precursors for geopolymer synthesis. Each clay was subjected to calcination at 700 °C and analyzed using DTA/TG, grain size distribution measurements, XRD, and FTIR spectroscopy before and after heat treatment. The results...

Pure model geopolymers present a promising potential for high-temperature binders for structural or coating applications. However, their well-known chemical stability, which can reach 1400°C in the case of K-activated geopolymer, is accompanied by deleterious dimensional behavior, with significant shrinkage on heating. The work in the present paper...

The huge availability of volcanic deposits in Mt. Etna volcano and the wide use of volcanic materials as aggregates in local architecture encouraged us to apply them in alkaline environment to produce geopolymeric binders to restore historical buildings of Mt. Etna area. Two clusters of samples for each volcanic precursor (volcanic ash and ghiara p...

This work aims to synthetize geopolymer composites and study the influence of the aluminum concentration, wollastonite and glass fibers on the properties of the fresh and hardened material. To this end, different metakaolin, wollastonite and glass fibers contents were used to synthesize geopolymer composites. The effect of reinforcement elements on...

Dimension reduction, cost efficiency, and environmental sustainability are important factors in absorbent designs. Geopolymers represent an eco-friendly and cost-efficient solution for such applications, and the objective of this study is to develop new geopolymer-based composites with tailored dielectric properties. To develop such composites, dif...

This work aims to adapt a formulation of a geopolymer composite to elaborate complex shapes. Here a hollow cylinder is chosen to investigate different possible solutions: building process according to the formulation. To this end, different content of metakaolin, wollastonite, and glass fibers was used to identify the feasibility of shaping of the...

Fire resistance performance is one of the most important requirements in geological storage conditions in order to improve the resistance of storage packages to high thermal constraints (in the case of a fire for example). With the need to develop new fire-resistant materials, the aim of the present study was to develop fire-resistant geopolymer bi...

The thermal behavior of a model MK based K‐geopolymer (Si/Al = 1.38 and K/Al = 0.68; obtained by alkaline activation of a very pure metakaolin) was investigated between room temperature and 1400°C in order to evaluate its potentiality for high‐temperature applications. The purpose of our study was to monitor the behavior of a geopolymer during a te...

The thermal behavior of a model MK‐based K‐geopolymer was investigated between room temperature and 1400°C in order to evaluate its potentiality for high‐temperature applications. The purpose of our study was to monitor the behavior of a geopolymer during a temperature rise in order to better understand its variations with respect to temperature. T...

The influence of drying on the microstructure, physical and chemical properties of some tropical wood species has been investigated using thermogravimetric analysis, differential scanning calorimetric (DSC), FTIR-ATR spectroscopy, mercury intrusion porosimetry (MIP) and environmental scanning electron microscopy (ESEM) analysis. Eleven tropical spe...

The influence of drying on the microstructure, physical and chemical properties of some tropical wood species has been investigated using Thermogravimetric Analysis, Differential Scanning Calorimetric (DSC), FTIR-ATR spectroscopy, Mercury Intrusion Porosimetry (MIP) and Environmental Scanning Electron Microscopy (ESEM) analysis. Eleven tropical spe...

This work investigates how silica and lignocellulose additives afect the production of metakaolin based-geopolymer foam flters. Lignocellulosic material from wood powder sawdust (S), silica from rice husk ash (RHA), calcined (Sa) and uncalcined (Sab) sand were separately used together with high amorphous silica fume (foaming agent) and integrated i...

In this study, the formulation of alkali-activated grouts based on Callovo-Oxfordian argillite, with a long setting time (up to 24 h) and a moderate pH value (10–11), is investigated. The first step was to select the reference mixture based on calcined argillite (650 °C) and metakaolin. The selected binder presented an initial setting time of 11 h...

This study aims to develop a geopolymer binder, which requires a control of the reactive mixture setting time, viscosity and pH value. A previous study underlines the possibility of controlling the setting time, viscosity and pH value of geopolymer binders by the addition of phosphate- or boron–based compounds. To understand the structural evolutio...

Decreasing the pH value of a concentrated sodium silicate solution while maintaining its basic environment, largely affects solution stability. The charge modification induces by the presence of acidic species is expected to destabilize initial equilibrium, thus affecting original structure. Acidification along with dilution of a concentrated sodiu...

The progressive addition of the reactive silica from rice husk ash (10–50 wt%) changes the phases evolution and the microstructure of the laterites based geopolymer composites. It was found that the presence of soluble silica enhanced the formation of Si–(A)-OH–Fe bonds and changed considerably the FTIR and XRD patterns of the products: polysialate...

Knowledge of alkaline silicate solutions is crucial in order to optimize geopolymer properties. Geopolymers are new binders resulting from the activation of an aluminosilicate by an alkaline solution. It is well established that the solution reactivity strongly affects the geopolymerization and therefore the geopolymer working properties. As a cons...

This study presents a new design of a reduced volumetric ultra‐wideband (UWB) antenna using innovative dielectric based on the use of geopolymer material which is safe and eco‐friendly. The created antenna is intended to radiate in the air. The impedance mismatch due to interface dielectric/air at the aperture of the antenna imposes to choose diele...

This work aims to study the effect of the addition of reactive or unreactive aluminosilicate sources on the geopolymerisation reaction, and therefore on the geopolymer's working properties. To this end, six formulations with different metakaolin content, as well as the potential addition of mica fillers, were synthetized and investigated over time....

To improve the thermal stability of porous geopolymers, metabauxite and metatalc were used as partial replacement of metakaolin. The results of optical microscopy, Scanning Electron Microscopy (SEM), thermal sintering, mercury intrusion porosimetry (MIP) and hot disk investigations, were used to establish the effective stability of the porous compo...

The aims of this study correspond to (i) determine the feasibility of synthesize geomaterial from two main Pb-contaminated mining sediments (Sed1 and Sed2) without prior activation in substitution to metakaolin (MK), (ii) understand the mechanisms involved toward two types of silicate solution (Na and K one), and (iii) to evaluate the change in the...

The aim of this investigation was the development of a geopolymer grout. To achieve this goal, it is necessary to control the characteristics of the reactive mixture (i.e., between the dissolution of the mineral source and the consolidation of the binder) and its setting time. The targeted application (geological radioactive waste disposal) require...

Acid-based geopolymers exhibit interesting properties, such as higher temperature resistance (up to 1450 °C) and better mechanical properties, as compared to alkali-based geopolymers. The aim of this work was to highlight the origin of water and thermal resistances of acid-based geopolymers, demonstrated in our previous study, by ²⁷ Al, ²⁹ Si and ³...

The French national radioactive waste management agency (Andra) is studying the building of a deep geological disposal for High and Intermediate Level radioactive waste. If accepted, the disposal will lead all along the operating period to the excavation of a large amount of host rock, mainly constituted by argillite. With the aim of using this by‐...

Keywords: Geopolymer Silicate solution Raman spectroscopy Ionic conductivity + n si n n () (Al) (M) Viscosity A B S T R A C T Geopolymers are new binders resulting from the activation of an aluminosilicate source by an alkaline solution. It is well-established that the precursors that are used affect geopolymer formation. This study focuses on how...

The valorization of oyster or mussel shells toward metakaolin-based geomaterials was investigated. The aim is to better understand the feasibility and the reaction involved during the incorporation of shells (natural or cal-cined) into a metakaolin-based alkaline solution for potential building or contaminants sorbents applications. Mixtures are re...

The influence of spark plasma sintering (SPS) parameters (temperature, time, pressure) and the role of particle size on densification, microstructure and mechanical properties of commercial additive-free TiB2, SiC and composites thereof were studied by X-ray diffraction, scanning electron microscopy, the ultrasonic method and indentation. Three par...

Different formulations of geopolymers were synthesized in acidic media (phosphoric acid) starting from three different raw metakaolin materials to identify compositions of interest. Four different property groups were highlighted based on the most favorable thermal and water resistance properties (while maintaining acceptable mechanical properties)...

The sol–gel synthesis of yttrium aluminum garnet (YAG) was performed using different metal precursors (salts and alkoxides of aluminum and yttrium) and metal concentrations (up to a concentration factor of 7.4). The cross-reactivity of the aluminum and yttrium precursors is not clear, and generally, the sol–gel process leads to polyphasic samples c...

Alkaline silicate solutions have many applications, including sand agglomeration and geopolymer production. To ensure the widespread use of these applications, it is necessary to identify the parameters controlling their reactivity and interactions with other materials, such as sand and metakaolin. It has been evidenced that the key parameters for...

This study aims to understand the thermal behaviour of argillite based alkali-activated materials. Thermally heated argillites with different processes (furnace and flash process) and two alkaline solutions based on potassium or on a mix of potassium and sodium were used to synthesize consolidated materials. Then, the thermal resistance of the synt...

Here, the valorization of Callovo-Oxfordian (COx) argillite from the geological layer focused by the Cigéo project (Industrial Center for Geological Disposal of radioactive waste) is studied by Andra. Its reuse by alkali-activation is studied in order to develop thermally resistant binders. The thermal properties of various argillite-based samples...

Pyrolysis is an innovative environmentally-friendly process to thermally treat biomass residues at low temperatures and in the absence of oxygen without releasing suspended particles, smoke or greenhouse gases. The obtained solid residue is called biochar. The aim of this work is to characterize four biochar by-products and to evaluate the feasibil...

If accepted, the construction of Cigéo, a French geological disposal facility for radioactive waste, will lead to the excavation of a large quantity of Callovo-Oxfordian (COx) argillite. The valorization of this raw material by alkaline activation was studied. For this, COx argillite without and with thermal treatment at 750 °C using furnace and fl...

Two new designs of reduced volumetric ultra-wideband antennas (UWB) are proposed in this paper. These antennas are intended to radiate in the air medium over the frequency band of 0.3-3GHz. This work demonstrates that the combination of innovative dielectric materials along with either resistive load or the association of the radiation provided by...

The purpose of this study is the development of new aggregates based on geopolymer formulations in order to replace commercial lightweight aggregates (LWAs), which require high energy consumption due to its industrial sintering process. Geopolymers are innovative materials which are synthesized at low temperature and which exhibit efficient mechani...

Porous composites with the principal class of porosity in the range of those presented in the literature as ideal for the moisture control capacity of building environment are described. In the course of the design of the matrices, micrometric pores are introduced to give to the pore systems a bi- or multimodal characters with the aim of improving...

This study focused on identifying the differences in a clay quarry that is used in brick production to understand the variation between samples based on two kinds of clays: the first kind was suitable for brick production, but the second one did not show good production efficiency. Various samples were characterized by physical and chemical methods...

The present study aims to determine the influence of aluminum and calcium availability from two different aluminosilicate sources (COx argillite and sediment), thermally treated at 750 °C, on the formation, the structure and the working properties of the resulting alkali-activated materials. Despite their similar chemical composition, some differen...

This study reports on the stereo digital image correlation (SDIC) method and its extension in the case of fracture analysis. The aim of this work is to propose an improvement to the SDIC method for solving uncertainty problems in the vicinity of a discontinuous displacement field (cracks). It was developed using the classical minimization process,...

This study focused on understanding the behavior of brick clay containing a low calcium amount in an alkaline silicate solution. Silicate solutions were used and calcium (in calcite mineral form) was added during the brick clay preparation. The addition of calcium induces (i) a delay in the oligomer formation, (ii) a modification of the polycondens...

This study was undertaken to valorize naturally occurring clays in the synthesis of new geopolymers materials from the mixture of commercial metakaolins and calcined clays (550 °C). For the purpose of this work, three raw clay samples were collected from various locations in Tunisia where clayey deposits extended over large areas. A simple synthesi...

Alkaline silicate solutions are used for different industrial applications. Structural studies of these solutions performed by fourier transform infrared and nuclear magnetic resonance spectroscopies have shown the presence of cyclic species. However, these techniques do not allow determining the variations of chain and ring size depending on the c...

The effects of alkaline solution and calcined clays on vibrational spectra and mechanical properties were studied on several geopolymer samples prepared from two alkaline solutions (S1, S2), calcined clays and three metakaolins. Structural evolution of the prepared geopolymers was characterized using FTIR spectroscopy and compression tests. Our res...

Brick clay mixtures are raw materials with the potential for use in geomaterials other than tiles or bricks. This study concerns the effect of mixed alkali cation solutions on the polycondensation reactions of geomaterials based on brick clay mixtures. To evidence the feasibility and the understanding of such effects, FTIR and Raman spectroscopy, t...

A considerable quantity of Callovo-Oxfordian (COx) argillite will be excavated due to deep geological radioactive waste disposal. Till now, there is no viable solution to make use of the excavated argillite. This paper investigates the possibility of producing alkali-activated materials based on argillite. The raw argillite is mainly composed of il...

Due to their interesting properties, geopolymers have found various applications in different domains. The evaluation of the dielectric properties of a geopolymer matrix for RF applications is innovative. In this context, this paper focuses, first, on the evaluation of the suitability of a geopolymer matrix with dielectric materials, and then on th...

A brick clay mixture from a company localized in the north west of France is used for this study. The feasibility of producing geopolymer materials from a clay mixture was investigated. The final aim is to find a new application for this aluminosilicate material. One metakaolin (for a reference), the brick clay mixture, and the clay mixture calcine...

This chapter examines how the interaction between the geopolymer binder and alkaline earth cations such as Ca, Mg or Sr to determine the effect of the presence of these elements on polycondensation reactions. Fourier-transform infrared (FTIR) spectroscopy in ATR mode was used to investigate the structural evolution of the geopolymer mixtures. The F...

This chapter focuses on the influence of alkali cations in pure and mixed alkali cation solutions on the polycondensation reaction during geopolymer formation. Metakaolin is the most used raw material for studies because it allows inhibition of the purity issues and provides a model geopolymer. Another key parameter is the characteristics of the si...

The purpose of the present study is to control the polycondensation reaction of various geopolymer samples based on six metakaolins and two potassium alkaline solutions with different reactivities. First, metakaolin characterization revealed three levels of reactivity, which increase essentially with the increase in the degree of purity, amorphous...

Algerian kaolinic clay from Tamazert and two alkalines solutions (potassium silicate and mixed potassium sodium silicate solutions) whose Si/K and Si/(K+Na) molar ratio of 0.58 and 0.80 respectively are used for the preparation of geopolymers. The raw material calcined at 750°C characterized by XRD and DTA/TG. The results carried out by infrared sp...

The aim of this study is to assess the effects of the addition of aluminum (NaAlO2) into the activating solution on the geopolymerization reactions and the characteristics of the porous network. It was established by liquid state NMR that the speciation of the aluminosilicate oligomers and then the mean degree of polymerization were modified by the...

This paper presents results from experimental studies on the thermal resistance and dilatometry analysis of various geopolymer formulations, which were prepared by mixing alkaline solutions, metakaolin and reinforcements. Nine compositions were tested by dilatometric analysis and thermal resistance at high temperature (800 °C). Structural and micro...

Geopolymers are innovative mineral binders. These materials are still under research development in order to better understand the formation mechanism, the local structure and the final working properties. The aim of this study is to provide predictive tools permitting to control the geopolymerisation reaction. At first, it is important to determin...

Clay based ceramic composite materials with hydraulic permeability were elaborated using sawdust as porogent agent. Their mechanical, morphological, microstructural and pore network properties were investigated. Mixtures in various ratios of two kaolinite clay minerals, Ba (highly plastic) and Va (sand-rich) constitute the five ceramic matrixes stu...