Effect of hydromagnesite addition on the properties and water resistance of magnesium oxysulfate (MOS) cement

• Published in: Cement and concrete research Vol. 143; p. 106387
• Main Authors: Guan, Yan, Hu, Zhiqi, Zhang, Zuhua, Chang, Jun, Bi, Wanli, Cheeseman, Chris R., Zhang, Tingting
• Format: Journal Article
• Language: English
• Published: Elmsford Elsevier Ltd 01.05.2021; Elsevier BV
• Subjects: Amorphous materials; Basic magnesium carbonate; Cement; Compressive strength; Hydromagnesite; Magnesium oxide; Magnesium oxysulfate cement; Physical properties; Rietveld method; Water resistance; Water stability; Rietveld method; Hydromagnesite; Water resistance; Magnesium oxysulfate cement
• ISSN: 0008-8846; 1873-3948
• DOI: 10.1016/j.cemconres.2021.106387

Magnesium oxysulfate (MOS) cement exhibits excessive cracking when exposed to water because of the reaction of residual MgO that forms extensive Mg(OH)2, which significantly limits the application breadth of MOS cement. This study investigates the effects of the addition of hydromagnesite ((MgCO3)4·Mg(OH)2·4H2O) on the hydration products of MOS cement and the microstructure and physical properties of MOS paste samples. It was found that the addition of hydromagnesite increased the compressive strength and water resistance of MOS cement. This effect is mainly due to the reaction between hydromagnesite and free MgO present in the cement that forms magnesium carbonate (MgCO3·Mg(OH)2·3H2O) and acts as an additional binding phase. The use of hydromagnesite as an additive for improving the water resistance of MOS cement leads to a decrease in the residual MgO content and improves the water stability of amorphous materials.