Carbonation and radiative cooling properties of calcium silicates for cement applications

PhD Program

Speaker

Ebtisam Tarek Mohammed Saeed

When

2026/05/29
12:00

Place

Sala de Grados, Facultad de Psicología EHU (second floor), Donostia / San Sebastián

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PhD Thesis defense by Ebtisam Tarek Mohammed Saeed

Supervisor: Jorge Sánchez Dolado (CFM, DIPC Associate), and Cyril Aymonier (ICMCB)

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.