Nanocomposites and nanomaterials

Rheological and early age properties of cement pastes modified with nano- and micro-particles used for shielding applications
Sikora P.1,2, Chougan M.3, Liard M4., Ghaffar S.H.3
1 Faculty of Civil and Environmental Engineering, West Pomeranian University of Technology in Szczecin, Al. Piastow 50, 70-311 Szczecin, Poland 
E-mail: pawel.sikora@zut.edu.pl
2 Building Materials and Construction Chemistry, Technische Universität Berlin, Gustav-Meyer-Allee 25, 13355 Berlin, Germany
3 Department of Civil and Environmental Engineering, Brunel University London, Uxbridge, UB8 3PH, United Kingdom
4 Sika Technology AG – Central Research, Zurich, Switzerland

In recent years, there has been growing concern regarding the production of lead-free radiation shielding materials. Concrete is known to be one of the cheapest radiation shielding materials with a good capability to immobilize various materials (including waste and by-products). Moreover, concrete offers both satisfactory neutron and gamma-ray shielding properties. To develop concrete with adequate satisfactory radiation shielding properties, a high dosage of additives is required. However, the incorporation of nano- and micro-particles, especially those heavy-weight used as a cement replacement, might lead to significant alteration of the fresh cement pastes properties such as rheology and setting time. Therefore, to produce lead-free radiation shielding concrete, knowledge on the performance of cement paste incorporating nano- and micro-particles is required. 
This work aims to evaluate the effects of the most popular lead-alternative nano- and micro-particles on fresh and early age cement paste mechanical properties. Cement was replaced with additives up to 30 wt.-%, and the effects of various particles, including Fe3O4, Bi2O3, B4C, and Gd2O3 on the heat of hydration, setting time, rheology, and strength properties were evaluated. Moreover, a comprehensive study on the thixotropic behaviour of cement pastes was performed. This comprehensive study could lead to potential technology adaptation, where new materials have been developed for implementation.