Effect of drying methods on the microstructures and properties of cured calcium aluminate cement pastes

Abstract

Drying process is necessary in the preparation and application of refractory castables. In this work, the effects of conventional drying, microwave drying and freeze drying on the composition and properties of cured calcium aluminate cement (CAC) pastes were comparatively investigated. The differences in the microstructures evolution process under various drying mechanisms were discussed. The results show that metastable CAH₁₀ and C₂AH₈ are completely transformed into stable phases in the conventional dried pastes, while a small amount of flaky C₂AH₈ remained in pastes dried via microwave. Nevertheless, the major hydrates in the freeze-dried pastes are CAH₁₀ and C₂AH₈. In addition, the pores in pastes dried by microwave are mainly distributed in the range of 20–2000 nm, while the freeze-dried pastes contain more gel pores and show higher elastic modulus. A new approach to effectively regulate the pore structure of CAC bonded materials via non-conventional drying methods is proposed in the present work.