QIN Ji, HE Xing, CHANG Ying

(School of Materials and Chemical Engineering, Hubei University of Technology, Wuhan 430070, Hubei, China)

Abstract: α-Hemihydrate gypsum (α-HH) with excellent dispersibility and crystallinity was prepared by using a pressurized aqueous solution method with lactic acid gypsum as the raw material. The as-prepared products were characterized by using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and laser particle size analysis (LPS). The 2 h flexural strength of the α-hemihydrate gypsum product was evaluated by using a flexural strength tester. Effects of organic acid content on crystal morphology and crystallinity, glycerol content on crystal dispersibility and crystallinity of α-high strength gypsum were studied and discussed. It was found that the product obtained by adding 0.11 wt.% modifier possessed a high crystallinity, an average crystal size 29.36 μm and an average aspect ratio of about 1, while the flexural strength of the sample formed from these gypsum binders after 2 h hardening reached 5.68 MPa.

Key words: α-hemihydrate gypsum; dispersibility; crystallinity; flexural strength