Crystallization Characteristic of Periclase in Clinker and Effect of Mg²⁺ on Hydrate of Cement Pastes

Abstract

Crystallization characteristic of periclase in clinker and effect of Mg²⁺ on hydrate of cement pastes were investigated. Morphologies and relative content of periclase were characterized with scanning electron microscopy and X-ray diffraction. Derivative thermogravimetry analysis and backscattered electron imaging were used to characterize the effect of Mg²⁺ on hydrate of cement pastes. The experimental results show that in ample space, periclase forms octahedron structure, and subhedral or anhedral crystal is formed in limited space. Due to the accelerated burning temperature and prolonged holding time, coarse pericalase crystals are formed. Mg(OH)2 particle thickness increases due to faster crystal growth rate along c axis at later age. Mg²⁺ can substitute Ca²⁺ in C-S-H or C-A-H to form magnesium silicate hydrate(M-S-H) or magnesium aluminate hydrate(M-A-H), and the substitution extent for C-A-H is higher than that for C-S-H. Cured in 80 °C water, the decalcification rate of C-A-H in pastes is higher than that cured in 50 °C water. M-A-H with an atomic Mg/Al ratio of 2 is formed through substitution of Ca by Mg in C-A-H.

Keywords

high magnesium clinker / periclase / magnesium silicate hydrate / magnesium aluminate hydrate

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