Bonding Strength and Durability of Spray Printing Ultra-Rapid Setting Magnesium Phosphate Cement Coating

doi:10.16552/j.cnki.issn1001-1625.2024.1356

Abstract

Abstract: In order to ensure the working time, the magnesium phosphate cement coating needs to be mixed with a large amount of retarder under the conventional spraying process, which not only weakens the early hour strength of the coating, but also increases the cost of raw materials. Based on this, this paper adopted the integrated spray printing equipment with mixing and spraying function, and realized the preparation and spraying construction of the ultra-rapid setting magnesium phosphate cement coating without retarder by the spray mode of dry powder inlet and wet material outlet. The development law of bonding strength of the coating under different curing environments and the improvement effect of frost resistance under freeze-thaw cycle were further studied. The results show that when the magnesium-phosphorus molar ratio (M/P) is 6 and the water-binder ratio (W/B) is 0.18, the bonding strength of the ultra-rapid setting magnesium phosphate cement coating is the best, and the bonding strength can reach 2.46 MPa after 60 d. Compared with the air curing at the same age, the bonding strength of the ultra-rapid setting magnesium phosphate cement coating in the early stage of seawater and salt lake brine curing is significantly increased by 43.2% and 22.5%, respectively. In the early stage of curing, seawater and salt lake brine can promote the hydration reaction of unreacted magnesium oxide and potassium dihydrogen phosphate in the coating to generate more struvite, thereby enhancing the bonding strength of the coating. The bonding strength of the coating decreases slightly at the later stage of curing, but it can still be maintained 0.84 MPa.Compared with uncoated concrete, the compressive strength retention rate and relative dynamic elastic modulus of ultra-rapid setting magnesium phosphate cement coated concrete increase by 111.5% and 33.1%, respectively, and the mass loss rate decreases by 76.3% after 150 times freeze-thaw cycles. The research results provide a theoretical basis for the application of spray printing ultra-rapid setting magnesium phosphate cement coating in concrete structure protection engineering under harsh environment.

Key words: magnesium phosphate cement coating, spray printing, ultra-rapid setting, seawater, salt lake brine, bonding strength, frost resistance

CLC Number:

TU525.9

LIANG Yun, YU Qiuchun, DENG Yongjie, DONG Sijia, LI Weihong, LI Dongwei. Bonding Strength and Durability of Spray Printing Ultra-Rapid Setting Magnesium Phosphate Cement Coating[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2025, 44(6): 1967-1978.

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