Nanocomposites and nanomaterials

Synthesis of Bi2O3-SiO2 and Gd2O3-SiO2 core-shell structures towards improvement of fresh and hardened properties of cement-based composites
Sikora P.1, Cendrowski K.1, Federowicz K.1, Techman M.1
1 Faculty of Civil and Environmental Engineering, West Pomeranian University of Technology in Szczecin, Al. Piastow 50a, 70-311 Szczecin, Poland 
E-mail: pawel.sikora@zut.edu.pl

Concrete is one of the most widely used materials for radiation shielding in radiation therapy facilities, hospitals, nuclear reactors as well as in military applications. In general, materials such as lead, with a high atomic number (High-Z), are preferred for absorbing ionizing radiation. Unfortunately, in the recent years serious concerns are raised regarding use of lead due to its potentially hazardous effects. 
In recent years, special attention has been particularly paid to nanosized admixtures, which lead to far greater improvements in cementitious systems, in comparison to their micro-sized counterparts. Inclusion of high dosage of metal oxide nanoparticles results in decrement of heat of hydration as well as can negatively affect mechanical, microstructural and durability-related properties of cement-based composites. Therefore, methods towards improving the reactivity of metal oxide nanoparticles are required.
This study is devoted to synthesis of Bi2O3-SiO2 and Gd2O3-SiO2 core-shell structures towards improvement of fresh and hardened properties of cement-based composites. Hydration studies including isothermal calorimetry and thermogravimetric analysis were performed. In addition, rheological and mechanical properties were determined.
Study showed that cement can be effectively replaced with up to 10 wt% of nanoparticles without deteriorating substantially the properties of Portland cement paste. Therefore, inclusion of such nanoparticles into cementitious system can find its utilization in production of radiation shielding cement-based composites.
Acknowledgement: This research was funded in part by the National Science Centre, Poland within Project No. 2020/39/D/ST8/00975 (SONATA-16).