Formation of chabazite in mixes of calcium aluminate cement and silica fume used for caesium immobilization

Abstract

The immobilization of caesium with a mix of calcium aluminate cement (CAC) and silica fume (SF) was studied at 50°C. The presence of caesium within the hydration solution leads to the formation of a zeolitic phase of the chabazite family, which immobilizes caesium within the cementitious mix. A severe leach test shows that the immobilization is efficient. Chabazite is also formed when a Cs solution is in contact with an already hydrated CAC-SF mix. The structure of zeolites involves ceramic bonds that are more stable with heat treatment than hydrate bonds, which explains why chabazite is not destroyed by heat treatment at a temperature as high as 750°C. The presence of chabazite is therefore interesting for any application that requires thermal treatment.

Application of Geopolymer in Stabilization/Solidification of Hazardous Pollutants: A Review

“…Ordinary Portland cement (OPC) is, of course, broadly adopted for the S/S process, due to its easy handling, low cost, and good S/S performance [ 17 ]. In addition, some other types of cement, such as magnesia-based cement, calcium aluminate cement, sulfate aluminate cement, etc., have been also adopted for the S/S of heavy metals [ 18 , 19 , 20 , 21 , 22 ]. However, cement-based S/S of waste is relatively fragile to physical and chemical degradation processes, which depends on factors, such as permeability, chemical and mineralogical composition, and microstructure [ 23 ].…”

Confining caesium in expanded natural Perlite

“…Furthermore, the measured solubility of pollucite is lower while the leakage of Cs from pollucite are three orders of magnitude less than those for silicate glasses. 1 Therefore, various synthetic methods have been considered for pollucite using self-propagating high-temperature synthesis (SHS), 2 reaction between gaseous Cs and fly ash, 3 hydrothermal, 4 arc melting technique, 5 ion exchange in zeolites 6 and crystallization from a glass. 7 Moreover, pollucite is a naturally occurring mineral with a three-dimensional structure that contains and irreversibly traps more Cs.…”

Capacidade De Adições Minerais Em Mitigar O Ataque Por Sulfatos De Sódio E Magnésio Em Argamassas De Cimento Portland

“…Por outro lado, a contagem dos picos em + 9,30º 2, segundo Fryda et al (1996), podemos ser explicados pela formação do mineral de Chabasita em sua composição calcítica ( [ 4 • 2 ] 12 · 6 2 ). Segundo os autores, a formação deste mineral se dá pelo elevado teor de sílica reativa no sistema e em conjunto a temperaturas mais elevadas, a partir de 40 ºC.…”