Journal of Food, Agriculture and Environment

Fire resistance of magnesium phosphate cement

Author(s):

Zhong-hua Li

Recieved Date: 2013-07-25, Accepted Date: 2013-10-13

Abstract:

In order to clear the service performance of magnesium phosphate cement under fire, the change laws of the compressive strength, chemical composition and appearance were researched after heated and preserved for 2 h in 100, 200, 500 and 800°C. Its deterioration mechanism was analyzed by DSC-TG and XRD compared with the sample under 20°C. The results show the compressive strength loss rate of magnesium phosphate cement increases with increase of temperature heated, and especially obviously after 100 and 800°C. The loss ratio of the compressive strength decreases with increases of water binder ratio and result from fly ash and slag added. P/M didn’t affect the loss ratio of the compressive strength. The colour of magnesium phosphate cement is changed from khaki, pale yellow, pale grey, black to finally gray. White crystals only separate out from a sample at 100, 200, 500°C and specimen heated at 100°C. DSC-TG and XRD results show MgNH₄PO₄·6H₂O is main products of the magnesium phosphate cement. It suffers from chemical reaction at 106-135°C and 643-683°C range. It firstly losses volatile NH₃ and generates MgHPO₄. Subsequently MgHPO₄ is dehydrated and changed into Mg₂P₂O₇. This causes a sudden drop in the compressive strength. Adjustment of water binder ratio and adximtures added doesn’t change deterioration mechanism of magnesium phosphate cement.

Keywords:

Magnesium phosphate cement, deteriorating mechanism, compressive strength, fire resistance

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Journal: Journal of Food, Agriculture and Environment
Year: 2013
Volume: 11
Issue: 3&4
Category: Environment
Pages: 2542-2546

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