Preparation of BeliteCalcium Sulfoaluminate Cement Clinker and Activation of Belite by Boron Dopants

Abstract:

Belitecalcium sulfoaluminateferrite (BCSAF) cement clinker was prepared from clay, bauxite and calcium carbonate. The influence that the mineral composition has on the compressive strength of cement paste was then analyzed. Boron was doped as a stabilizer, and the effects that Boron has on clinker calcination and hydration were investigated. The structure and composition of the BCSAF clinker was analyzed based on Xray powder diffraction, scanning electron microscopy, and thermal analysis. The results demonstrate that the earlyage strength of the cement paste depends mostly on the hydration of calcium sulfoaluminate, and that belite hydration makes great contributions to the lateage strength development. Ferrite is beneficial to the mass transfer during calcination. However, when the ferrite content is too high, the activity of belite tends to decrease. The doping of Boron, on one hand, helps to stabilize the belite at the α’ polymorph, improving the hydration activity of BCSAF cement at early ages. On the other hand, it prompts the chemical reactions during the clinker calcination, and reduces the formation of the transient product, gehlenite. As a result, the compressive strength of the cement paste at 3 d age is improved due to the Boron doping.

Key words:Belite; calcium sulfoaluminate; mineral composition; boron dopants