ED Sciences Chimiques
Carbonation and radiative cooling properties of calcium silicate for cement applications
by Ebtisam Tarek Mohammed SAEED (ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux)
The defense will take place at 12h15 - Sala de Grados, second floor University of the Basque Country (EHU/UPV), Facultad de Psicología, Tolosa Hiribidea 70, 20018 Donostia / San Sebastián, Gipuzkoa
in front of the jury composed of
- María Saiz SANTOS - Professeure - University of the Basque Country UPV/EHU - Examinateur
- María José COCERO - Full professor - University of Valladolid - Rapporteur
- François MARTIN - Full professor - University of Toulouse III - Examinateur
- Laurence CROGUENNEC - Directrice de recherche - Université de Bordeaux - Examinateur
- Katerina IOANNIDOU - Chargée de recherche - Université de Montpellier - Rapporteur
Calcium silicate minerals have attracted increasing attention due to their unique physicochemical properties and their potential applications in industrial and environmental fields. In particular, they have been widely investigated for CO₂ sequestration through mineral carbonation. However, natural silicate minerals often exhibit limited reactivity and typically require harsh reaction conditions, such as elevated temperatures, high pressures, or long reaction times, to achieve significant CO₂ conversion. Furthermore, the extraction and processing of natural silicates involve labor-intensive operations and specialized equipment to obtain sufficiently pure and finely ground materials. These limitations highlight the need for synthesizing nanostructured silicate precursors with enhanced reactivity that can capture CO₂ efficiently under mild conditions. In this work, Xonotlite, (Ca₆Si₆O₁₇(OH)₂) calcium silicate hydrate, was synthesized using supercritical water flow technology (SCW), enabling rapid production of highly pure xonotlite in just 7–10 seconds, with tunable crystal sizes. An amorphous form of xonotlite was also produced under ambient conditions, further reducing energy requirements. The carbonation of xonotlite results in the formation of stable calcium carbonate phases and amorphous silica, offering a promising pathway for carbon capture, utilization, and storage (CCUS) while generating valuable mineral by-products for various industrial applications. Furthermore, nanostructured wollastonite was synthesized through the dehydration of xonotlite at relatively low temperature in the presence of water. The resulting wollastonite exhibits higher specific surface area and enhanced dissolution kinetics compared with natural wollastonite, leading to improved carbonation performance. Carbonation experiments demonstrated significant CO₂ uptake and the formation of stable calcium carbonate together with amorphous silica. The results show that amorphous xonotlite promotes rapid formation of multiple CaCO₃ polymorphs, whereas highly crystalline xonotlite converts more slowly into stable calcite. Despite these differences in reaction kinetics, all synthesized phases exhibit comparable CO₂ storage potential. Beyond carbon sequestration, the development of advanced cement-based materials capable of improving the energy efficiency of buildings has also become an important research topic. One promising approach is passive radiative cooling, a phenomenon in which materials emit thermal radiation through the atmospheric transparency window (8–13 µm) while reflecting most of the incoming solar radiation. Materials exhibiting high solar reflectance and strong infrared emissivity can passively dissipate heat into outer space, enabling surfaces to cool below ambient temperature without energy consumption. Although radiative cooling technologies have been extensively studied in coatings and photonic materials, their integration into structural construction materials such as cement-based composites remains relatively unexplored. Xonotlite also exhibits favorable optical properties for radiative cooling applications, which have not previously been reported in the literature. Its nano- and microscale fibrous morphology, highly scattering bright-white microstructure, and high refractive index promote strong solar reflectance, while its intrinsic Si-O vibrational modes and porous framework enhance mid-infrared emissivity. Cement pastes incorporating synthesized xonotlite were therefore prepared and evaluated in terms of hydration behavior, mechanical performance, and optical properties. The results demonstrate that xonotlite can improve both the functional and mechanical performance of cement-based materials while providing enhanced radiative cooling capability. This thesis therefore introduces xonotlite as a novel reactive calcium silicate candidate for mineral carbonation and radiative cooling applications.
ED Entreprise Economie Société
The weight of inequality: environmental shocks, socio-economic gaps and obesity in Chile and India
by Valentina ALVAREZ SAAVEDRA (BSE - Bordeaux sciences économiques)
The defense will take place at 14h00 - Salle de séminaires BSE 16 Av. Léon Duguit, 33600, Pessac
in front of the jury composed of
- Matthieu CLEMENT - Professeur des universités - Université de Bordeaux - Directeur de these
- Pierre LEVASSEUR - Chargé de recherche - INRAE - CoDirecteur de these
- Julie LOCHARD - Professeure des universités - Université Paris-Est Créteil - Rapporteur
- Isabelle CHORT - Professeure des universités - Université de Pau et des Pays de l'Adour - Rapporteur
- Luca TIBERTI - Associate Professor - Università degli studi di Firenze - Examinateur
- Eric ROUGIER - Professeur des universités - Université de Bordeaux - Examinateur
Climate change, social inequality, and obesity are deeply interconnected crises of the 21st century. The rapid rise of overweight and obesity, especially in emerging economies, reflects structural constraints. Once associated with affluence, obesity now disproportionately affects poorer groups, and particularly women. Environmental shocks—including climate variability and natural disasters—amplify these vulnerabilities by disrupting livelihoods, diet quality, and opportunities for physical activity. Their combined effects fall disproportionately on vulnerable populations, trapping them in cycles of disadvantage with major implications for sustainable development and social justice. This thesis explores key relationships among environmental, economic, gender, and nutritional inequalities. Focusing primarily on Chile, an emblematic case of high inequality, climate vulnerability, and obesity prevalence, and complemented by evidence from India, a context marked by entrenched gender norms, the thesis comprises four independent empirical studies. Chapter 1 shows that weather anomalies exacerbate municipal income inequality in Chile primarily by increasing top income shares. Chapter 2 shows that temperature shocks increase bodyweight among low socio-economic status individuals through reductions in diet quality and physical activity, without notable effects on higher-status groups. Chapter 3 exploits the unexpected timing of the 2010 Chile earthquake to identify short-term increases in obesity, particularly among women and disadvantaged households. Chapter 4 examines how gender norms shape women's nutritional outcomes in India, showing that different dimensions of inequality, have distinct effects on bodyweight, contributing to the double burden of malnutrition. The findings highlight how environmental shocks and social inequality produce unequal nutritional outcomes. Although grounded in Chile and India, they speak to broader global challenges and underscore the need for integrated policies that combine climate adaptation, social protection, and equitable food and health systems. They also emphasize the importance of targeted interventions to protect vulnerable populations.