Performance of cement-slag-titanate nanofibers composite immobilized radioactive waste solution through frost and flooding events

Abstract

Innovation of cement-based composites is a recently strongly emerging technology. Nanotechnology is one of the potential alternatives to improve cement characteristics and to decrease the amount of cement used in various applications, which consequently reduces the energy required for cement production and carbon dioxide emission caused by cement industry. The improvement of cementitious materials is still an important target to produce modified compounds of valuable mechanical, chemical and physical characterizations. In this paper, Portland cement mixed with iron slag was hydrated with an aqueous titanate nanofibers suspension to create cement nanocomposites as environmentally friendly material with novel properties. In this sense, nanoparticles as additive material allow for improving the mechanical durability of cement and retard the permeability of cement-based materials. SEM, FT-IR and X-ray diffraction analyses confirmed the Ca(OH)2 conversion towards calcium silicate hydrate. Porosity and compressive strength measurements were also performed through variable parameters and under different conditions. Durability tests and chemical stabilization were carried out at freezing/thawing condition during extended cycles of up to 6 months. The effect of flooding in various aqueous media including acidic and alkaline ones was evaluated during extended periods of immersion. Moreover, the radioactive contaminant 137Cs was immobilized by the novel cement nanocomposite to test the nanocomposite’s chemical stability by monitoring the leaching of 137Cs. Resulting data were used to positively assess the feasibility of this compound to be used for immobilization of radioactive and other hazardous wastes. The produced composite attained proper consistency when exposed to frost attack or flooding in various media up to 180 days.