Effect of early hydration temperature on hydration product and strength development of magnesium phosphate cement (MPC)

Journal Article · Tue Dec 15 00:00:00 EST 2015 · Cement and Concrete Research

DOI:https://doi.org/10.1016/J.CEMCONRES.2015.07.005· OSTI ID:22696529

You, Chao ^[1]; Qian, Jueshi ^[1]; Qin, Jihui ^[1]; Wang, Hongtao ^[2]; Wang, Qingzhen; Ye, Ziqi ^[1]

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1. College of Materials Science and Engineering, Chongqing University, Chongqing 400045 (China)
2. Department of Chemistry and Materials, Logistical Engineering University, Chongqing 401311 (China)

This paper investigates the effect of early hydration temperatures on hydration products and strength development of magnesium phosphate cement (MPC). MPC paste specimens with borate contents of 3%, 6%, 9% and 12% are prepared and cured in different air temperatures and in the adiabatic condition. The internal hydration temperatures are measured by pre-embedded temperature probes. MPC samples with different hydration temperatures are also obtained by using thin slice samples. The hydration products in MPC samples with different hydration temperatures are analyzed by X-ray diffractometer (XRD) and scanning electron microscope (SEM) and the strength development is also measured. The results show that NH{sub 4}MgPO{sub 4}·6H{sub 2}O is the major hydration product and beneficial to strength development of MPC at hydration temperature below 70 °C. NH{sub 4}MgPO{sub 4}·H{sub 2}O is another major product, which significantly decreases the strength, when the temperature is higher than a critical temperature between 70 °C and 75 °C. NH{sub 4}MgPO{sub 4}·H{sub 2}O can directly form in the MPC paste, and comes from the decomposition of NH{sub 4}MgPO{sub 4}·6H{sub 2}O when the temperature is above 75 °C. With temperature elevation and duration extension, NH{sub 4}MgPO{sub 4}·6H{sub 2}O decomposes rapidly, and even entirely when the temperature is above 100 °C. The borate content has no effect on the types of major hydration products and the critical temperature.

• OSTI ID: 22696529
• Journal Information: Cement and Concrete Research, Vol. 78, Issue Part B; Other Information: Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0008-8846
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BORATES
CEMENTS
CRITICAL TEMPERATURE
DECOMPOSITION
ELECTRON SCANNING
HYDRATION
MAGNESIUM PHOSPHATES
MAXIMUM PERMISSIBLE CONCENTRATION
SCANNING ELECTRON MICROSCOPY
WATER
X RADIATION
X-RAY DIFFRACTION
X-RAY DIFFRACTOMETERS