We studied three metakaolinite-based geopolymers with Si/Al molar ratios of ∼ 2. Two of the alkali silicate solutions were Na-based and the other was K-based. Differential thermal/thermogravimetric analyser results were obtained up to 1000°C in air. Infrared spectroscopic studies were made at temperatures up to 700°C. Solid state nuclear magnetic resonance studies of 23 Na (and 29 Si) were also conducted after heating to temperatures up to 600°C. High-resolution transmission electron microscopy confirmed the structure of one of the Na-based geopolymers to be amorphous at the ∼ 10 nm scale on heating from ambient to 500°C and this was consistent with wide-angle X-ray diffraction data obtained at temperatures up to 435°C. It is proposed that the water which is essential for the geopolymer reaction in these materials to take place is present after curing as 1) "free" water, 2) interstitial water and 3) OH' groups. After curing a geopolymer in a closed container the "free" water is present in the intergranular regions, plus a thin external film. After heating to 150°C, this water which constitutes ∼60% of the starting water, is lost. Nearly all of the remaining interstitial water is lost after heating to 300°C. Hydroxyl groups in the geopolymers were present at quite low concentrations, together with carbonate groups.

D S Perera

E R Vance

K S Finnie

M G Blackford

J V Hanna

D J Cassidy

Ceramic Transactions Series

Ceramic Transactions

Disposition of Water in Metakaolinite Based Geopolymers

偏高岭土基地质聚合物中水的赋存状态

Disposition of Water in Metakaolinite Based Geopolymers

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