Effect of magnesium hydroxide on the properties of fireproof coatings for steel structure based on magnesium phosphate cement

Magnesium phosphate cement, renowned for its exceptional fire resistance, has been a key area of research in fireproof coatings for steel structures. This study introduces a significant amount of magnesium hydroxide to replace the dead-burned MgO in magnesium phosphate cement. The goal is to enhance fireproof performance by capitalizing on magnesium hydroxide's outstanding flame retardant and fire resistance properties. This paper primarily investigates the effects of substantial amounts of magnesium hydroxide on the compressive strength, dry density, and bonding strength of coatings and the quality, phase, and micro-morphology of coatings before and after flaming thermal shock. The findings indicate that when the substitution rate of magnesium hydroxide surpasses 50 %, the coatings exhibit commendable performance characteristics. After a curing duration of 28 days, the coatings attain a compressive strength of 0.5 MPa, a bonding strength exceeding 0.04 MPa, and a dry density remaining below 650 kg/m³. Furthermore, the coatings demonstrate remarkable resilience to thermal shock, maintaining structural integrity even under extreme flame thermal shocks exceeding 1000 °C, without any observable cracking or spalling. This noteworthy performance underscores the significant potential of this research in the industrial landscape.