A Study of Alteration Phases on Glass-Bonded Zeolite and Sodalite using the Vapor Hydration Test

Abstract

This paper focuses on the reaction of glass-bonded zeolite and sodalite ceramic waste forms, naturally occurring sodalite, and their respective alteration phases that formed after reaction in a Vapor Hydration Test (VHT). Scanning electron microscope (SEM) analysis of the glass-bonded zeolite and sodalite samples indicate that NaCI is the major alteration phase present, along with KCI, Na-Al-Si, and Na-K-Ca-Al-Si phases. The order of precipitation of salt crystals from ceramic waste form occurred in the sequence NaCl ⇒ KC1 ⇒ CaCl2 and MgCl2. We also found aluminum silicate phases containing Ca, Mg, K-Na-Ca, K-Mg, Na-K-Mg, K-Ca-Na-Mg, as well as CaCO3, SiO2. The ratio of Si/Al in the alteration phases was noted to increase from approximately 1.5 to 5 during the progressive alteration of the samples. This trend indicates a relative increase in the contribution of silicon from the relatively Si-rich glass regions of the samples over time. Phases enriched in Cs, Ba and rare earth elements (RE) were also observed on the altered samples. Alteration phases initially appeared along the micro-fractures during the early stages of alteration. The number of micro-fractures, density of alteration phase cover, and grain size of alteration phases increased with reaction time and temperature.

Department(s)

Geosciences and Geological and Petroleum Engineering

Keywords and Phrases

Aluminum Compounds; Calcium Compounds; Ceramic Materials; Fracture; Glass Bonding; Hydration; Magnesium Compounds; Potassium Compounds; Radioactive Waste Disposal; Silicates; Sodium Chloride; Zeolites; Sodalite; Vapor Hydration Test; Radioactive Waste Vitrification

International Standard Serial Number (ISSN)

0272-9172

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 1999 Materials Research Society (MRS), All rights reserved.

Publication Date

01 Jan 1999

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