PhD Thesis Defense | Ebtisam Tarek Mohammed Saeed

Published: Maiatza 19, 2026

Carbonation and radiative cooling properties of calcium silicates for cement applications

May 29, 12:15

Sala de Grados, Facultad de Psicología

(second floor)

Candidate: Ebtisam Tarek Mohammed Saeed

Supervisors: Dr. Jorge Sánchez Dolado, and Dr. Cyril Aymonier

 

SUMMARY

The construction sector is a major contributor to global CO2 emissions and urban heat buildup, creating the need for sustainable cementitious materials. This thesis investigates the synthesis and multifunctional applications of calcium silicate minerals, particularly xonotlite, for CO2 sequestration and passive radiative cooling in cement-based materials. Xonotlite was synthesized using supercritical water flow technology, enabling rapid production of highly pure nanostructured material within 7 s, and was further converted into β-wollastonite at low temperature (460 °C) compared to conventional methods. The CO2 sequestration potential of these materials was evaluated by aqueous mineral carbonation at 50 bar and 60 °C. Results showed that carbonation behavior depends on precursor crystallinity, which controls dissolution rate, supersaturation, and calcium carbonate polymorph formation. Xonotlite achieved 60 wt.% CaCO3, and synthetic wollastonite reached up to 66 wt.% CaCO3. In addition, xonotlite was investigated as an additive for passive radiative cooling cement. Xonotlite exhibited high solar reflectance (Rsun= 95%) and high thermal emissivity (εAW= 0.93). When incorporated into cement, solar reflectance increased to 96%, while mechanical properties improved, with the dynamic elastic modulus increasing from 44 GPa to 66 GPa.

These results demonstrate that xonotlite-based materials enable multifunctional cement systems combining CO2 sequestration, improved mechanical performance, and radiative cooling for sustainable construction.

Rapid supercritical water synthesis enables the production of highly pure nanofibrous xonotlite within few seconds. The synthesized xonotlite demonstrates novel multifunctional applications in CO2 mineral carbonation and passive radiative cooling cement materials with enhanced solar reflectance and thermal emissivity for mitigating CO2 emissions and urban heat island effects.

BIOGRAPHY

About me and the output of PhD work:

I am a Ph.D. researcher in cotutelle between the University of the Basque Country (UPV/EHU) in the doctoral program Physics of Nanostructures and Advanced Materials and University of Bordeaux in Physical Chemistry of Condensed Matter. My research is centered on the development of advanced materials using supercritical water synthesis for CO2 sequestration and sustainable cementitious materials for passive radiative cooling applications.

During my Ph.D., I contributed as first author to the European patent application Process for Capturing and/or Sequestering Carbon Dioxide with Xonotlite (EP26305237.5, 2026). I am also author and co-author of Q1 publications related to the development of sustainable cementitious composites and cool concrete systems using carbonated food-waste-derived materials for urban heat island mitigation and CO₂ capture applications (https://orcid.org/0000-0003-4928-5425). My broader research interests also include nanofluids, electrochemical materials, and thermochromic coatings.

I have presented my PhD research at international conferences, including the 1st RILEM International Conference on Mineral Carbonation for Cement and Concrete 2024 in Aachen, Germany, and the 20th European Meeting on Supercritical Fluids (EMSF 2024) in Maribor, Slovenia. I was also awarded the Best Oral Presentation at the II PhD Day 2025 of the Faculty of Chemistry (EHU/UPV).

Prior to my Ph.D., I completed a Master’s degree in Nanoscience at the University of the Basque Country and a Master’s degree in Applied Chemistry at University of Jaén, with research experience in ZnO nanostructures and functional inorganic nanomaterials for energy and environmental applications.

My main goals are to contribute bridge the gap between scientific research and real-world sustainable technologies with environmental impact, and to always make my mom proud.