Hydration behavior of magnesium potassium phosphate cement and stability analysis of its hydration products through thermodynamic modeling

Journal Article · Tue Aug 15 04:00:00 EDT 2017 · Cement and Concrete Research

DOI:https://doi.org/10.1016/J.CEMCONRES.2017.03.015· OSTI ID:22697120

Zhang, Tao ^[1]; Chen, Huisu ^[1]; Li, Xiangyu ^[2]; Zhu, Zhigang ^[1]

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1. Jiangsu Key Laboratory of Construction Materials, School of Materials Science and Engineering, Southeast University, Nanjing 211189 (China)
2. College of Architecture and Civil Engineering, Taiyuan University of Technology, Taiyuan (China)

Magnesium potassium phosphate cement (MKPC) is normally applied in civil engineering because of its short setting time and superior mechanical properties. This study investigates the hydration behavior and hydration products of MKPC influenced by molar ratio between magnesia and phosphate (M/P ratio) through thermodynamic method. Results show that the composition of ultimate hydration products are controlled by concentration of KH{sub 2}PO{sub 4} and MgO, activity of water and pH value of solution. When M/P ratio is lower than 0.64, the hydration product is MgHPO{sub 4}·3H{sub 2}O; When M/P ratio is between 0.64 and 0.67, the hydration products are MgHPO{sub 4}·3H{sub 2}O and Mg{sub 2}KH(PO{sub 4}){sub 2}·15H{sub 2}O. When M/P ratio is between 0.67 and 1.00, hydration products are Mg{sub 2}KH(PO{sub 4}){sub 2}·15H{sub 2}O and KMgPO{sub 4}·6H{sub 2}O; When M/P ratio is higher than 1.00, the hydration product is KMgPO{sub 4}·6H{sub 2}O together with unreacted MgO. This study also investigated the effect of additives, namely B(OH){sub 3}, H{sub 3}PO{sub 4}, K{sub 2}HPO{sub 4} and KH{sub 2}PO{sub 4}. - Highlights: • A database particularly for MKPC system at 25°C, 0.1 MPa was established and verified. • The pH value corresponding to specific M/P ratio in MKPC system is successfully predicted at 25°C, 0.1 MPa. • The composition of hydration products influenced by M/P ratio and some additives is successfully predicted at 25°C, 0.1 MPa.

• OSTI ID: 22697120
• Journal Information: Cement and Concrete Research, Journal Name: Cement and Concrete Research Vol. 98; ISSN CCNRAI; ISSN 0008-8846
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
BORIC ACID
CEMENTS
CIVIL ENGINEERING
HYDRATION
MAGNESIUM OXIDES
MAXIMUM PERMISSIBLE ACTIVITY
MECHANICAL PROPERTIES
PH VALUE
PHOSPHORIC ACID
POTASSIUM PHOSPHATES
PRESSURE RANGE MEGA PA
THERMODYNAMICS
WATER