The Improvement Effects of NaH2PO4 and KH2PO4 on the Properties of Magnesium Oxysulfate Cement

• Published in: Journal of Wuhan University of Technology. Materials science edition Vol. 36; no. 1; pp. 50 - 57
• Main Authors: Wang, Nan, Yu, Hongfa, Bi, Wanli, Guan, Yan, Gong, Wei, Zhang, Na, Wu, Chengyou
• Format: Journal Article
• Language: English
• Published: Wuhan Wuhan University of Technology 01.02.2021; Springer Nature B.V
• Subjects: Additives; Cement; Cementitious Materials; Chemistry and Materials Science; Compressive strength; Infrared analysis; Infrared spectroscopy; KDP crystals; Magnesium; Materials Science; Microstructure; Phase composition; Porosity; Potassium phosphates; Scanning electron microscopy; Sodium phosphate; Thermogravimetric analysis; X-ray diffraction; compressive strength; microstructure; magnesium oxysulfate cement; volume stability; phosphates
• ISSN: 1000-2413; 1993-0437
• DOI: 10.1007/s11595-021-2377-y

Sodium dihydrogen phosphate (NaH 2 PO 4 ) and potassium dihydrogen phosphate (KH 2 PO 4 ) were selected as additives for magnesium oxysulfate (MOS) cement. The phase composition and the microstructure of MOS cement were characterized using X-ray diffraction (XRD), thermogravimetric analysis (TG-DSC), Flourier transform infrared spectroscopy (FT-IR), mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). It is found that both NaH 2 PO 4 and KH 2 PO 4 lead to an increase in the compressive strength and an improvement in the volume stability of MOS cement. The XRD, MIP and SEM results show that the addition of NaH 2 PO 4 or KH 2 PO 4 does not change the phase composition of MOS cement but promotes the formation of strength phase of 5Mg(OH) 2 ·MgSO 4 ·7H 2 O (5·1·7 phase). This phase brings a considerable improvement in the microstructure of MOS cement, which has a positive effect on the properties of MOS cement.