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1、Performance of magnesium phosphate cement at elevated temperaturesPerformance of magnesium phosphate cement at elevatedtemperaturesLi Yue a ,b ,Shi Tongfei a ,b ,Chen Bing c ,?,Li Yaqiang a ,baThe Key Laboratory of Urban Security and Disaster Engineering,MOE,Beijing University of Technology,Beijing
2、100124,PR China bBeijing Key Lab of Earthquake Engineering and Structural Retro?t,Beijing University of Technology,Beijing 100124,PR China cDepartment of Civil Engineering,Shanghai Jiaotong University,Shanghai 202140,PR Chinah i g h l i g h t sWe studied effect of elevated temperature on MPC.Propert
3、ies of MPC after exposure to high temperature were evaluated. The presence of ?y ash and sand decrease residual strength of MPC. Microstructural examination of MPC after exposure to high temperatures.a r t i c l e i n f o Article history:Received 17February 2021Received in revised form 25March 2021A
4、ccepted 1May 2021Available online 16May 2021Keywords:MPCHigh temperature Residual strength Microstructurea b s t r a c tThis research studied effect of elevated temperature on properties of magnesium phosphate cement (MPC).Properties,including strength,colour,mass loss,and microstructure,of MPC spec
5、imens before and after exposure different high temperature were measured or observed in this paper.Seven sample mixtures contained varying amounts of ?y ash and sand are considered in the experimental program.The mechanical properties of MPC were measured by heating 40?40?160mm sample to 130,500and
6、1000C at a rate of 10C/min.The obtained results demonstrate that strength of MPC decreased sig-ni?cantly when the temperature passed 130C.After 130C,the amplitude of strength decreased of MPC became less with the increasing of temperature.The results of Differential thermal analysis (DTA)and thermo-
7、gravimetric analysis (TG)indicate that the crystal water in MKP 6H 2O were lost at the tempera-ture of 125C.The loss of crystal water in MKP 6H 2O was the main reason of strength decreasing and mass loss of MPC after exposure to high temperature.The results also show that the presence of ?y ash and
8、sand decrease residual strength of MPC.2021Elsevier Ltd.All rights reserved.1.IntroductionMPCs,formed by through-solution acid-based reaction between dead burnt magnesia and phosphate salts,were ?rst discovered and developed as dental cement in the late 19th century 14.In 1970,magnesium phosphate ce
9、ments were developed as rapid repair materials in civil engineering 5.During decades of devel-opment,MPCs have been employed in many ?elds.These include the uses of:stabilized and solidi?ed,light magnesium phosphate cement foamed material,dental or bone restorations,repair and rehabilitation of stru
10、cture and 3D powder printing materials 612.MPCs have several advantages against conventional Portland cement such as rapid setting time,high early strength,good bonding with Portland cement,little drying shrinkage andgood resistance to abrasion 1316.These superior properties endow MPCs with the pote
11、ntial to be widely used in structures.Traditional magnesium phosphate cement was prepared from the chemical reaction of dead burned magnesia oxide (MgO)and ammonium dihydrogen phosphate (NH 4H 2PO 4)919.The chem-istry and structure of similar materials were studied by Abdelrazig et al.13.The hexahyd
12、rate was identi?ed as the main reaction product in the commercial MPC mortar,which is the most stable.However,the main problem with these mortars is that during for-mation and even after,they tend to release ammonia.Hence,though they are comparatively inexpensive,their use is limited to outdoor appl
13、ication.But,one interesting feature of Sugama and Kukackas study 18attracts researchersattention,is that the strength kept rising as they heated this cement up to 1300C.The stability of MPCs at high temperature is an important characteristics because conventional Portland cements are not stable at h
14、igh temperatures and,hence,cannot be used for refrac-tory applications.Phosphate cements can be very useful in thishttp:/ Ltd.All rights reserved.?Corresponding author.Tel.:+86139*.E-mail address:hntchenhttp:/ (B.Chen).respect because they can be cast into required shapes at room tem-perature and si
15、nteres at high temperature.Due to the release of pungent ammonia,potassium dihydrogen phosphate (KH 2PO 4)was proposed to replace ammonium dihydrogen phosphate to pre-pare MPCs,which solved the drawback of the preparation of the MPC and proved that the main product was MgKPO 46H 2O.Chau et al.15investigated the structure of the hydration product that adds KH 2PO 4and indicated that the structure of MgKPO 46H 2O was the same as that of struvite.However,the literature on MKP min-eral is scare.Sivaprasad et al.and Wagh et al.consider this materi
