U-Phase [(CaO)[ (Al2O3) (SO3)(Na2O)]:nH2O] in Hydrating Cement with Sodium Sulfate

Author(s): Yuka Morinaga(1), Tomohiro Kajio(1), Elakneswaran Yogarajah(1), Toyoharu Nawa(1), and Eiji Owaki(2)
Paper category: Proceedings
Book title: Proceeding of the 71st RILEM Annual Week & ICACMS 2017
Editor(s): Manu Santhanam, Ravindra Gettu, Radhakrishna G. Pillai, Sunitha K. Nayar
ISBN:978-2-35158-195-7, 978-2-35158-190-2 (Set)
e-ISBN: 978-2-35158-191-9
Publisher: RILEM Publications SARL
Publication year: 2017
Pages: 547-556
Total Pages: 10
Language : English

Abstract:  Low-level nuclear waste of boiling water reactor (BWR) power plants consists of highly concentrated (㹼25 wt. %) Na2SO4, and the wastes are solidified with cementitious materials at elevated temperature. U-Phase [(CaO)㹶(Al2O3) (SO3)㹷(Na2O)㹸:nH2O] could be formed at high concentration of Na2SO4 solution and may cause deterioration of the cementitious materials through formation of the phase or transformation of U-Phase into Ettringite. A very few studies have reported the formation of U-phase in cement system at high concentration of Na2SO4, but the mechanism by which the U-Phase form, its stability in cementitious materials, and the conditions on the transformation of U-Phase into other phases are still not understood. Therefore, purpose of this study is to synthesize and characterize of U-phase to determine its thermodynamic properties at various temperature. XRD, 27Al MAS NMR and XRF were used for solid characterization. Based on the experimental results, the structure of U-Phase was proposed.

Online publication :2017
Publication type :full_text
Public price (Euros) : 0.00